# The Effects of Cold Exposure (Cold Water Immersion, Whole- and Partial-Body Cryostimulation) on Cardiovascular and Cardiac Autonomic Control Responses in Healthy Individuals: A Systematic Review, Meta-Analysis and Meta-Regression.

Hela Jdidi, Benoit Dugué, Claire de Bisschop, Olivier Dupuy, Wafa Douzi

► To cite this version:

Hela Jdidi, Benoit Dugué, Claire de Bisschop, Olivier Dupuy, Wafa Douzi. The Effects of Cold Exposure (Cold Water Immersion, Whole- and Partial-Body Cryostimulation) on Cardiovascular and Cardiac Autonomic Control Responses in Healthy Individuals: A Systematic Review, Meta-Analysis and Meta-Regression. Journal of Thermal Biology, 2024, pp.103857. 10.1016/j.jtherbio.2024.103857. hal-04554821

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# The Effects of Cold Exposure (Cold Water Immersion, Whole- and Partial- Body Cryostimulation) on Cardiovascular and Cardiac Autonomic Control Responses in Healthy Individuals: A Systematic Review, Meta-Analysis and Meta-Regression.

Hela Jdidi¹, Benoit Dugué¹≈, Claire de Bisschop¹≈, Olivier Dupuy¹,², Wafa Douzi¹

¹ University of Poitiers, Laboratory «Mobilité, Vieillissement, Exercice (MOVE)—UR 20296»
Faculty of Sport Sciences, 86000 Poitiers, France.

² University of Montreal, School of Kinesiology and Physical Activity Sciences (EKSAP),
Faculty of Medicine, , Montreal, QC HC3 3J7, Canada

≈ Equal contribution

hela.jdidi@univ-poitiers.fr; benoit.dugue@univ-poitiers.fr; Olivier.dupuy@univ-poitiers.fr;
claire.de.bisschop@univ-poitiers.fr; wafa.douzi01@univ-poitiers.fr

Corresponding author: [hela.jdidi@univ-poitiers.fr](mailto:hela.jdidi@univ-poitiers.fr)

University of Poitiers

8, allée Jean Monnet, 86 000 Poitiers - France

Tel : +33 6 27 77 22 83; Fax : +33 5 49 45 33 96

E-mail : [hela.jdidi@univ-poitiers.fr](mailto:hela.jdidi@univ-poitiers.fr)

**Data accessibility statement:** Data supporting our study findings are available within the article or supplementary materials.

**Funding Sources:** The authors declare that no financial support was received.

**Conflicts of interest:** The authors declare no conflict of interest.

**CRediT author statement:** W.D and H.J: Conceptualization, Literature search, Articles Screening, Data extraction, Formal analysis, Writing- Original draft preparation. W.D, H.J, B.D, C.d.B and O.D: Visualization, Investigation, Writing- Reviewing and Editing. W.D Supervision.

**Ethical Committee/Institutional Review Board (IRB) approval:** Not applicable

**Registration:** The review protocol was registered in PROSPERO under the ID: CRD42023467597, and it can be accessed via the following link: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=467597. No amendments have been made since its initial registration.
# The Effects of Cold Exposure (Cold Water Immersion, Whole- and Partial- Body Cryostimulation) on Cardiovascular and Cardiac Autonomic Control Responses in Healthy Individuals: A Systematic Review, Meta-Analysis and Meta-Regression.

Hela Jdidi¹, Benoit Dugué¹≈, Claire de Bisschop¹≈, Olivier Dupuy¹,², Wafa Douzi¹

¹ University of Poitiers, Laboratory «Mobilité, Vieillissement, Exercice (MOVE)—UR 20296»
Faculty of Sport Sciences, 86000 Poitiers, France.

² University of Montreal, School of Kinesiology and Physical Activity Sciences (EKSAP),
Faculty of Medicine, , Montreal, QC HC3 3J7, Canada

≈ Equal contribution

hela.jdidi@univ-poitiers.fr; benoit.dugue@univ-poitiers.fr; Olivier.dupuy@univ-poitiers.fr;
claire.de.bisschop@univ-poitiers.fr; wafa.douzi01@univ-poitiers.fr

Corresponding author: [hela.jdidi@univ-poitiers.fr](mailto:hela.jdidi@univ-poitiers.fr)

University of Poitiers

8, allée Jean Monnet, 86 000 Poitiers - France

Tel : +33 6 27 77 22 83; Fax : +33 5 49 45 33 96

E-mail : [hela.jdidi@univ-poitiers.fr](mailto:hela.jdidi@univ-poitiers.fr)

**Data accessibility statement:** Data supporting our study findings are available within the article or supplementary materials.

**Funding Sources:** The authors declare that no financial support was received.

**Conflicts of interest:** The authors declare no conflict of interest.

**CRediT author statement:** W.D and H.J: Conceptualization, Literature search, Articles Screening, Data extraction, Formal analysis, Writing- Original draft preparation. W.D, H.J, B.D, C.d.B and O.D: Visualization, Investigation, Writing- Reviewing and Editing. W.D Supervision.

**Ethical Committee/Institutional Review Board (IRB) approval:** Not applicable

**Registration:** The review protocol was registered in PROSPERO under the ID: CRD42023467597, and it can be accessed via the following link: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=467597. No amendments have been made since its initial registration.
**Abstract**

**Background:** Cryostimulation and cold-water immersion (CWI) have recently gained widespread attention due to their association with changes in cardiovascular and cardiac autonomic control responses. Therefore, the aim of the present systematic review and meta-analysis was to identify the global impact of such cold exposures on cardiovascular and cardiac autonomic activity.

**Methods:** Three databases (PubMed, Embase, Web-of-Science) were used. Studies were eligible for inclusion if they were conducted on healthy participants using cryostimulation and/or CWI. The outcomes included measurements of blood pressure (BP), heart rate (HR), and heart rate variability (HRV) indices: RR interval (RR), Root mean square of successive RR interval differences (RMSSD), low frequency band (LF), high frequency band (HF), and LF/HF ratio.

**Results:** Among the 27 articles included in our systematic literature review, only 24 were incorporated into the meta-analysis. Our results reveal a significant increase in HRV indices: RMSSD (Standardized mean difference (SMD) = 0.61, p<0.001), RR (SMD = 0.77, p<0.001), and HF (SMD = 0.46, p<0.001), as well as significantly reduced LF (SMD = -0.41, p<0.001) and LF/HF ratio (SMD = -0.25, p<0.01), which persisted up to 15 minutes following cold exposure. Significantly decreased heart rate (SMD = -0.16, p<0.05), accompanied by slightly increased mean BP (SMD = 0.28, p<0.001), was also observed. These results seem to depend on individual characteristics and the cooling techniques.

**Conclusion:** Our meta-analysis suggests that cryostimulation and/or CWI exposure enhance parasympathetic nervous activity. There is scarce scientific literature regarding the effect of individual characteristics on cold-induced physiological responses.

**KEYWORDS:** Cardiac autonomic control; Autonomic nervous system; Cardiovascular system; cold exposure; Cold water immersion; Partial-body cryotherapy/cryostimulation; Whole-body cryotherapy/cryostimulation.
**Abstract**

**Background:** Cryostimulation and cold-water immersion (CWI) have recently gained widespread attention due to their association with changes in cardiovascular and cardiac autonomic control responses. Therefore, the aim of the present systematic review and meta-analysis was to identify the global impact of such cold exposures on cardiovascular and cardiac autonomic activity.

**Methods:** Three databases (PubMed, Embase, Web-of-Science) were used. Studies were eligible for inclusion if they were conducted on healthy participants using cryostimulation and/or CWI. The outcomes included measurements of blood pressure (BP), heart rate (HR), and heart rate variability (HRV) indices: RR interval (RR), Root mean square of successive RR interval differences (RMSSD), low frequency band (LF), high frequency band (HF), and LF/HF ratio.

**Results:** Among the 27 articles included in our systematic literature review, only 24 were incorporated into the meta-analysis. Our results reveal a significant increase in HRV indices: RMSSD (Standardized mean difference (SMD) = 0.61, p<0.001), RR (SMD = 0.77, p<0.001), and HF (SMD = 0.46, p<0.001), as well as significantly reduced LF (SMD = -0.41, p<0.001) and LF/HF ratio (SMD = -0.25, p<0.01), which persisted up to 15 minutes following cold exposure. Significantly decreased heart rate (SMD = -0.16, p<0.05), accompanied by slightly increased mean BP (SMD = 0.28, p<0.001), was also observed. These results seem to depend on individual characteristics and the cooling techniques.

**Conclusion:** Our meta-analysis suggests that cryostimulation and/or CWI exposure enhance parasympathetic nervous activity. There is scarce scientific literature regarding the effect of individual characteristics on cold-induced physiological responses.

**KEYWORDS:** Cardiac autonomic control; Autonomic nervous system; Cardiovascular system; cold exposure; Cold water immersion; Partial-body cryotherapy/cryostimulation; Whole-body cryotherapy/cryostimulation.
Introduction

Cold exposure techniques such as whole-body cryostimulation (WBC), partial-body cryostimulation (PBC), and cold-water immersion (CWI) have recently gained widespread attention in the overall context of health and, more specifically recovery after exercise and rehabilitation. Cryostimulation refers to a technique of body cooling, in which individuals are exposed to extremely cold air (usually between -50°C and -160°C) for short periods of time (typically between 2 and 5 minutes). It encompasses two techniques, WBC wherein the individual is entirely exposed to cold air in an environmentally controlled chamber, and PBC, where the individual is similarly exposed, in a barrel-shaped device called cryo-sauna, while excluding the head. While cryotherapy and cryostimulation both refer to the same kind of cold stimulus, they involve patients in the former and healthy individuals in the latter. Cold water immersion entails immersing the entire body, except for the head, or the lower body up to the umbilicus, in water with temperatures typically below 15°C. These techniques are well-reputed for their potential benefits in terms of improved sleep quality and reduced pain, fatigue, inflammation, oxidative stress, and muscle soreness after physical exercise (Douzi et al., 2019b, 2019a; Moore et al., 2023). These features may be directly or indirectly related to changes in cardiovascular and cardiac autonomic control activities.

The autonomic nervous system (ANS) consists of two continuously active and functionally
distinct divisions, namely the parasympathetic nervous system (PNS) and the sympathetic
nervous system (SNS). The ANS plays an important role in the control of cardiac activity. At
rest, the coordinated activity of the PNS and the SNS helps to maintain stable heart rate (HR)
(Yugar et al., 2023). In this regard, heart rate variability (HRV) has been widely recognized as
a reliable and noninvasive method for the assessment of autonomic cardiovascular regulation
and sympatho-vagal interaction (Mäkinen et al., 2008). HRV is defined as a series of
measurements of successive RR interval (intervals between QRS complexes of normal sinus
depolarization) variations in the HR record (Sztajzel, 2004; van Ravenswaaij-Arts et al., 1993).
HRV assessment can be conducted by means of different methods. The time domain method
examines the variability of the RR intervals between consecutive heartbeats such as the root
mean square of successive RR interval differences (RMSSD), while the frequency domain
approach evaluates the power distribution of HR oscillations across different frequency bands
including low-frequency (LF), and high-frequency (HF) bands (Shaffer and Ginsberg, 2017;
van Ravenswaaij-Arts et al., 1993). Parasympathetic nervous system effects tend to be more
rapid (typically within 1 second) after a stimulus, as - compared to sympathetic activity, which
Introduction

Cold exposure techniques such as whole-body cryostimulation (WBC), partial-body cryostimulation (PBC), and cold-water immersion (CWI) have recently gained widespread attention in the overall context of health and, more specifically recovery after exercise and rehabilitation. Cryostimulation refers to a technique of body cooling, in which individuals are exposed to extremely cold air (usually between -50°C and -160°C) for short periods of time (typically between 2 and 5 minutes). It encompasses two techniques, WBC wherein the individual is entirely exposed to cold air in an environmentally controlled chamber, and PBC, where the individual is similarly exposed, in a barrel-shaped device called cryo-sauna, while excluding the head. While cryotherapy and cryostimulation both refer to the same kind of cold stimulus, they involve patients in the former and healthy individuals in the latter. Cold water immersion entails immersing the entire body, except for the head, or the lower body up to the umbilicus, in water with temperatures typically below 15°C. These techniques are well-reputed for their potential benefits in terms of improved sleep quality and reduced pain, fatigue, inflammation, oxidative stress, and muscle soreness after physical exercise (Douzi et al., 2019b, 2019a; Moore et al., 2023). These features may be directly or indirectly related to changes in cardiovascular and cardiac autonomic control activities.

The autonomic nervous system (ANS) consists of two continuously active and functionally
distinct divisions, namely the parasympathetic nervous system (PNS) and the sympathetic
nervous system (SNS). The ANS plays an important role in the control of cardiac activity. At
rest, the coordinated activity of the PNS and the SNS helps to maintain stable heart rate (HR)
(Yugar et al., 2023). In this regard, heart rate variability (HRV) has been widely recognized as
a reliable and noninvasive method for the assessment of autonomic cardiovascular regulation
and sympatho-vagal interaction (Mäkinen et al., 2008). HRV is defined as a series of
measurements of successive RR interval (intervals between QRS complexes of normal sinus
depolarization) variations in the HR record (Sztajzel, 2004; van Ravenswaaij-Arts et al., 1993).
HRV assessment can be conducted by means of different methods. The time domain method
examines the variability of the RR intervals between consecutive heartbeats such as the root
mean square of successive RR interval differences (RMSSD), while the frequency domain
approach evaluates the power distribution of HR oscillations across different frequency bands
including low-frequency (LF), and high-frequency (HF) bands (Shaffer and Ginsberg, 2017;
van Ravenswaaij-Arts et al., 1993). Parasympathetic nervous system effects tend to be more
rapid (typically within 1 second) after a stimulus, as - compared to sympathetic activity, which
typically takes more than five seconds (Nunan et al., 2010). Consequently, HF power has been proposed as an indicator of PNS modulation, while LF power predominantly represents SNS modulation (Harinath et al., 2005; Ramaekers, 1998). Of note, the LF/HF ratio is considered to reflect the sympatho-vagal balance (Malik, 1996). More specifically, an increased LF/HF ratio is often interpreted as an indicator of sympathetic dominance, while a decrease is thought to reflect parasympathetic drive. In addition, RMSSD is used as an additional indicator for PNS activity (Hausswirth et al., 2013; Westerlund et al., 2006).

Cold exposure is considered as a highly stressful situation imposed on the human body, which rapidly elicits the deployment of immediate, short-term regulatory mechanisms (Zalewski et al., 2013), most of which are associated with cardiovascular and cardiac autonomic control functions. Notably, a significant increase in plasma noradrenaline levels is observed, reflecting activation of the SNS (Hausswirth et al., 2013). Baroreceptors located in the carotid sinus and aortic arch stimulate autonomic bulb centers to initiate parasympathetic activation in view of restoring physiological homeostasis (Douzi et al., 2020; Pump et al., 2001). Increased parasympathetic activity at rest has long been linked with a better health and a state of well-being, which can be further enhanced through regular physical activity and healthy lifestyle habits (Louis et al., 2015; Udo et al., 2013). In this context, previous works have demonstrated that cryostimulation increases RR intervals, RMSSD and HF power values that correspond to increased PNS activity (Hausswirth et al., 2013; Zalewski et al., 2014b). Consequently, cold exposure may be an efficient intervention to enhance parasympathetic activity.

Numerous studies have investigated the cold exposure effects on blood pressure (Fonda et al., 2014; Muller et al., 2012; Zalewski et al., 2014b), HR (Hausswirth et al., 2013; Sramek et al., 2000; Theurot et al., 2021), and HRV (Louis et al., 2020, 2015; Zalewski et al., 2014b). Nevertheless, it is crucial to note that despite the pertinent findings revealed in individual studies, comprehensive synthesis in this area in the existing literature is still lacking. To the best of our knowledge, there is currently no available meta-analysis having examined the cardiac autonomic control and cardiovascular system responses after cryostimulation and/or CWI exposure. Therefore, a meta-analysis is of importance to fill this gap by providing a more comprehensive overview and robust analysis of the existing literature. The main objective of this review is therefore to identify the real impact of cryostimulation and/or CWI exposure on cardiovascular and cardiac autonomic control activity. Our study also aims to uncover potential moderating factors, such as participant characteristics (age, sex, body mass index and physical level), as well as moderators associated with cold exposure such as cooling technique, and
typically takes more than five seconds (Nunan et al., 2010). Consequently, HF power has been proposed as an indicator of PNS modulation, while LF power predominantly represents SNS modulation (Harinath et al., 2005; Ramaekers, 1998). Of note, the LF/HF ratio is considered to reflect the sympatho-vagal balance (Malik, 1996). More specifically, an increased LF/HF ratio is often interpreted as an indicator of sympathetic dominance, while a decrease is thought to reflect parasympathetic drive. In addition, RMSSD is used as an additional indicator for PNS activity (Hausswirth et al., 2013; Westerlund et al., 2006).

Cold exposure is considered as a highly stressful situation imposed on the human body, which rapidly elicits the deployment of immediate, short-term regulatory mechanisms (Zalewski et al., 2013), most of which are associated with cardiovascular and cardiac autonomic control functions. Notably, a significant increase in plasma noradrenaline levels is observed, reflecting activation of the SNS (Hausswirth et al., 2013). Baroreceptors located in the carotid sinus and aortic arch stimulate autonomic bulb centers to initiate parasympathetic activation in view of restoring physiological homeostasis (Douzi et al., 2020; Pump et al., 2001). Increased parasympathetic activity at rest has long been linked with a better health and a state of well-being, which can be further enhanced through regular physical activity and healthy lifestyle habits (Louis et al., 2015; Udo et al., 2013). In this context, previous works have demonstrated that cryostimulation increases RR intervals, RMSSD and HF power values that correspond to increased PNS activity (Hausswirth et al., 2013; Zalewski et al., 2014b). Consequently, cold exposure may be an efficient intervention to enhance parasympathetic activity.

Numerous studies have investigated the cold exposure effects on blood pressure (Fonda et al., 2014; Muller et al., 2012; Zalewski et al., 2014b), HR (Hausswirth et al., 2013; Sramek et al., 2000; Theurot et al., 2021), and HRV (Louis et al., 2020, 2015; Zalewski et al., 2014b). Nevertheless, it is crucial to note that despite the pertinent findings revealed in individual studies, comprehensive synthesis in this area in the existing literature is still lacking. To the best of our knowledge, there is currently no available meta-analysis having examined the cardiac autonomic control and cardiovascular system responses after cryostimulation and/or CWI exposure. Therefore, a meta-analysis is of importance to fill this gap by providing a more comprehensive overview and robust analysis of the existing literature. The main objective of this review is therefore to identify the real impact of cryostimulation and/or CWI exposure on cardiovascular and cardiac autonomic control activity. Our study also aims to uncover potential moderating factors, such as participant characteristics (age, sex, body mass index and physical level), as well as moderators associated with cold exposure such as cooling technique, and
cooled body areas. Subgroup and meta-regression analysis will be used to provide valuable guidance aimed at personalizing the intervention and at optimizing the use of cold exposure in various settings, including rehabilitation programs and post-exercise recovery. Furthermore, it is worth noting that time course analysis of cold exposure responses with regard to cardiovascular and cardiac autonomic control has not been incorporated into previous studies. Thereby, our meta-analyses may provide more complete and precise assessments of cold exposure effects and help to identify possible variations in physiological responses over time.

# Methods

## 1. Literature search strategy

PubMed, Embase and Web-of-Science databases were searched without time or filter limitations. The search syntax included the following keywords: [(Whole body cryotherapy) OR (Whole body cryostimulation) OR (partial body Cryotherapy) OR (partial body Cryostimulation) OR (Cryostimulation) OR (Cryotherapy) OR (Cold water immersion)] AND [(Hemodynamic responses) OR (heart rate) OR (heart rate variability) OR (autonomic nervous system) OR (sympathetic activity) OR (parasympathetic activity) OR (arterial blood pressure) OR (blood pressure)]. All possible medical subject headings (MeSH) terms and synonyms were mapped. Reference lists of the included articles were examined manually to collect further studies not electronically identified. Searches were completed in September 2023.

The search results were imported and processed using Rayyan systematic review software (Ouzzani et al., 2016). Two authors performed the search independently. Retrieved articles were assessed for duplication. After removing duplicates, studies were screened first by title and abstract and then by published full text.

## 2. Eligibility Criteria

The PECOS (participants, exposure, comparators, outcomes, and study design) model was used to determine the inclusion criteria. Studies were eligible for inclusion if they met the following criteria: (a) the studies were conducted on healthy participants using cold exposure interventions: WBC, wherein individuals are entirely exposed to cold air at temperatures below -50°C; PBC, wherein the body is similarly exposed, while excluding the head; and CWI, which involves immersing the entire body, except for the head, or the lower body up to the umbilicus, in water with temperatures below 15°C. No exposure duration limitation was applied (b) the experimental group results for different measurements before and after intervention were available (c) the studies used validated tests and outcomes regarding MAP, SBP, DBP, HR, R-R, RMSSD, LF, HF and/or LF/HF. Studies were excluded if: (a) the intervention was carried
cooled body areas. Subgroup and meta-regression analysis will be used to provide valuable guidance aimed at personalizing the intervention and at optimizing the use of cold exposure in various settings, including rehabilitation programs and post-exercise recovery. Furthermore, it is worth noting that time course analysis of cold exposure responses with regard to cardiovascular and cardiac autonomic control has not been incorporated into previous studies. Thereby, our meta-analyses may provide more complete and precise assessments of cold exposure effects and help to identify possible variations in physiological responses over time.

# Methods

## 1. Literature search strategy

PubMed, Embase and Web-of-Science databases were searched without time or filter limitations. The search syntax included the following keywords: [(Whole body cryotherapy) OR (Whole body cryostimulation) OR (partial body Cryotherapy) OR (partial body Cryostimulation) OR (Cryostimulation) OR (Cryotherapy) OR (Cold water immersion)] AND [(Hemodynamic responses) OR (heart rate) OR (heart rate variability) OR (autonomic nervous system) OR (sympathetic activity) OR (parasympathetic activity) OR (arterial blood pressure) OR (blood pressure)]. All possible medical subject headings (MeSH) terms and synonyms were mapped. Reference lists of the included articles were examined manually to collect further studies not electronically identified. Searches were completed in September 2023.

The search results were imported and processed using Rayyan systematic review software (Ouzzani et al., 2016). Two authors performed the search independently. Retrieved articles were assessed for duplication. After removing duplicates, studies were screened first by title and abstract and then by published full text.

## 2. Eligibility Criteria

The PECOS (participants, exposure, comparators, outcomes, and study design) model was used to determine the inclusion criteria. Studies were eligible for inclusion if they met the following criteria: (a) the studies were conducted on healthy participants using cold exposure interventions: WBC, wherein individuals are entirely exposed to cold air at temperatures below -50°C; PBC, wherein the body is similarly exposed, while excluding the head; and CWI, which involves immersing the entire body, except for the head, or the lower body up to the umbilicus, in water with temperatures below 15°C. No exposure duration limitation was applied (b) the experimental group results for different measurements before and after intervention were available (c) the studies used validated tests and outcomes regarding MAP, SBP, DBP, HR, R-R, RMSSD, LF, HF and/or LF/HF. Studies were excluded if: (a) the intervention was carried
out on patients or animals; (b) the cold exposure intervention was applied during or after
physical exercise. If cold exposure was used before physical activity, specifically for
therapeutic purposes or in settings where the measurements were taken after physical exercise,
the study was likewise excluded (c) the published works were in the form of books, citations,
conference proceedings, systematic reviews, and narrative reviews. Our study protocol was
conducted in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and
Meta-Analyses (PRISMA) statement (Page et al., 2021). The review protocol was registered in
PROSPERO, an international registry for systematic reviews (ID: CRD42023467597).

3. Data Extraction and Coding

Each study was blinded regarding authors, affiliations, and journals. The information were anonymized by a co-author, who was not involved in the data extraction process. The relevant details were revealed only after the data extraction process had been completed. Data were summarized in a spreadsheet (Microsoft Excel software). All included studies were coded using the following moderators: sex, age, body mass index, cold exposure intervention (cryostimulation, CWI), type of cryostimulation (WBC, PBC). The moderators were coded using a nominal scale. Mean and standard deviation were extracted from texts and tables. In cases where data were unavailable, the corresponding authors of the study were contacted. If no response was received, the study was excluded from our analysis. When data were presented in graphs, WebPlot Digitizer (Pacifica, CA, USA, Version: 4.5) was used (Drevon et al., 2017).

4. Methodological quality assessment

The methodological quality of the included studies was evaluated using the 11-item
Physiotherapy Evidence Database (PEDro) scale. A score of 1 indicates that the study satisfied
the item and a score of 0 indicates that the item was not satisfied (Maher et al., 2003). Two
authors independently assessed the methodological quality with discussion and search for
consensus over any difference in observed scores. Studies with a score equal or greater than 6
were considered to be high-quality, studies with scores equal to 4 or 5 were considered to be
medium-quality, and studies with a score lower than 4 were considered to be low-quality
(Maher et al., 2003).

5. Statistical analysis

Standardized mean differences (SMDs) between pre- and post-intervention for each
experimental group were calculated using Hedges' g (Hedges, 1981). Since the effect of a cold
exposure intervention may differ according to age, BMI, sex, or other moderators we used a
random effects model. The SMDs were weighted by the inverse of the variance to calculate an
overall effect and its 95% confidence interval (CI). If the CI crosses the value 0, it indicates a
out on patients or animals; (b) the cold exposure intervention was applied during or after
physical exercise. If cold exposure was used before physical activity, specifically for
therapeutic purposes or in settings where the measurements were taken after physical exercise,
the study was likewise excluded (c) the published works were in the form of books, citations,
conference proceedings, systematic reviews, and narrative reviews. Our study protocol was
conducted in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and
Meta-Analyses (PRISMA) statement (Page et al., 2021). The review protocol was registered in
PROSPERO, an international registry for systematic reviews (ID: CRD42023467597).

3. Data Extraction and Coding

Each study was blinded regarding authors, affiliations, and journals. The information were anonymized by a co-author, who was not involved in the data extraction process. The relevant details were revealed only after the data extraction process had been completed. Data were summarized in a spreadsheet (Microsoft Excel software). All included studies were coded using the following moderators: sex, age, body mass index, cold exposure intervention (cryostimulation, CWI), type of cryostimulation (WBC, PBC). The moderators were coded using a nominal scale. Mean and standard deviation were extracted from texts and tables. In cases where data were unavailable, the corresponding authors of the study were contacted. If no response was received, the study was excluded from our analysis. When data were presented in graphs, WebPlot Digitizer (Pacifica, CA, USA, Version: 4.5) was used (Drevon et al., 2017).

4. Methodological quality assessment

The methodological quality of the included studies was evaluated using the 11-item
Physiotherapy Evidence Database (PEDro) scale. A score of 1 indicates that the study satisfied
the item and a score of 0 indicates that the item was not satisfied (Maher et al., 2003). Two
authors independently assessed the methodological quality with discussion and search for
consensus over any difference in observed scores. Studies with a score equal or greater than 6
were considered to be high-quality, studies with scores equal to 4 or 5 were considered to be
medium-quality, and studies with a score lower than 4 were considered to be low-quality
(Maher et al., 2003).

5. Statistical analysis

Standardized mean differences (SMDs) between pre- and post-intervention for each
experimental group were calculated using Hedges' g (Hedges, 1981). Since the effect of a cold
exposure intervention may differ according to age, BMI, sex, or other moderators we used a
random effects model. The SMDs were weighted by the inverse of the variance to calculate an
overall effect and its 95% confidence interval (CI). If the CI crosses the value 0, it indicates a
non-statistically significant effect. Conversely, if the CI does not cross 0, it suggests a
statistically significant effect (Borenstein et al., 2009). Cohen's classification was used to
interpret the magnitude of SMD: < |0.50|: small; |0.50| to |0.80|: moderate; > |0.80|: large
(Cohen, 1998). The percentage of variability between studies was assessed using the I² statistic,
which represents statistical heterogeneity (Borenstein et al., 2009). I² values were classified as
low (25%), medium (50%) or high (75%) (Higgins et al., 2003). Subgroup and meta-regression
analyses were conducted to identify potential sources of variance and heterogeneity. Meta-
regression analysis was carried out for both categorical variables (i.e., sex [men vs women],
cryostimulation type [WBC vs PBC]), and continuous variables. For the latter, the means of
BMI, body fat %, and age were extracted from data presented in each individual study. The null
hypothesis according to which the effect of cold exposure was similar between categories of a
moderator variable was tested using a Q test based on analysis of variance (Borenstein et al.,
2009). Once the null hypothesis was rejected, pairwise comparisons were performed with a Z
test. The statistical significance level was set at p < 0.05.

To evaluate possible publication bias, funnel plot potential asymmetry test was used.
Stability of the pooled effect size was assessed by sensitivity analyses, which involves removing
individual studies from the analysis and calculating the impact of excluding each study on the
overall result. All calculations were made with Comprehensive Meta-analysis software (version
3; Biostat, Englewood, NJ, USA).

The level of evidence was established using a specific scale based on methodological quality
and statistical heterogeneity (Neal et al., 2016):

o The level of evidence was considered as strong when pooled results were obtained from three or more studies, including at least two high-quality studies that were statistically homogeneous.

o The level of evidence was considered as moderate when pooled results were obtained from multiple studies that were statistically heterogeneous, including at least one high-quality study, or, from multiple medium-quality or low-quality studies that were statistically homogeneous.

o The level of evidence was considered as limited when results were obtained from one high-quality study, or, from multiple medium- or low-quality studies that were statistically heterogeneous. The level of evidence was considered as very limited when it was obtained from one medium-quality study or one low-quality study.
non-statistically significant effect. Conversely, if the CI does not cross 0, it suggests a
statistically significant effect (Borenstein et al., 2009). Cohen's classification was used to
interpret the magnitude of SMD: < |0.50|: small; |0.50| to |0.80|: moderate; > |0.80|: large
(Cohen, 1998). The percentage of variability between studies was assessed using the I² statistic,
which represents statistical heterogeneity (Borenstein et al., 2009). I² values were classified as
low (25%), medium (50%) or high (75%) (Higgins et al., 2003). Subgroup and meta-regression
analyses were conducted to identify potential sources of variance and heterogeneity. Meta-
regression analysis was carried out for both categorical variables (i.e., sex [men vs women],
cryostimulation type [WBC vs PBC]), and continuous variables. For the latter, the means of
BMI, body fat %, and age were extracted from data presented in each individual study. The null
hypothesis according to which the effect of cold exposure was similar between categories of a
moderator variable was tested using a Q test based on analysis of variance (Borenstein et al.,
2009). Once the null hypothesis was rejected, pairwise comparisons were performed with a Z
test. The statistical significance level was set at p < 0.05.

To evaluate possible publication bias, funnel plot potential asymmetry test was used.
Stability of the pooled effect size was assessed by sensitivity analyses, which involves removing
individual studies from the analysis and calculating the impact of excluding each study on the
overall result. All calculations were made with Comprehensive Meta-analysis software (version
3; Biostat, Englewood, NJ, USA).

The level of evidence was established using a specific scale based on methodological quality
and statistical heterogeneity (Neal et al., 2016):

o The level of evidence was considered as strong when pooled results were obtained from three or more studies, including at least two high-quality studies that were statistically homogeneous.

o The level of evidence was considered as moderate when pooled results were obtained from multiple studies that were statistically heterogeneous, including at least one high-quality study, or, from multiple medium-quality or low-quality studies that were statistically homogeneous.

o The level of evidence was considered as limited when results were obtained from one high-quality study, or, from multiple medium- or low-quality studies that were statistically heterogeneous. The level of evidence was considered as very limited when it was obtained from one medium-quality study or one low-quality study.
○ The level of evidence was considered as very limited when pooled results were not statistically significant and came from multiple studies that were statistically heterogeneous.

## Results

### 1. Overall effect

The flow diagram of the search process is illustrated in Figure 1. The literature search led to the identification of 2669 potential studies eligible for inclusion in our analysis. Over 2000 (2172) articles were screened after removing duplicates, and 40 were assessed for eligibility. Thirteen studies (Barwood et al., 2017; Bonde-Petersen et al., 1992; Damijan and Uhrynski, 2012; Fox et al., 2003; Gregson et al., 2011; Hayward, 1984; Hayward and Eckerson, 1984; O'Brien et al., 2000; Tipton et al., 2000, 1998; Tipton and Golden, 1987; Versteeg et al., 2023; Zhang et al., 2003) were excluded from our analysis. The reasons for exclusion of each study are detailed in Appendix 1 (Supplementary material (SM)). Twenty-seven articles were included in our systematic review. Among them, 3 studies (Mawhinney et al., 2020; Westerlund et al., 2006, 2004) were excluded from the meta-analysis and meta-regression owing to the unavailability of relevant data. Finally, 24 articles were included in the meta-analysis and meta-regression. No additional articles were manually identified by examining the reference lists of the articles included.

A summary of the included studies is presented in Table 1. Additionally, the results of individual studies and pooled effect size are graphically displayed in forest plots (Appendix 2, see SM). Funnel plots used to identify a possible publication bias are presented in Appendix 3 (see SM). Symmetrical distribution of all measures around the mean effect size indicates that the sampling error was random. The results of leave-one-out sensitivity analysis showed that the estimated effect of cold exposure on all cardiovascular and autonomic nervous system variables is robust and not driven by any single study (Appendix 4, see SM). The PEDro scores obtained from each included study are presented in Table 2. The methodological quality average was 6.00 ± 1.06, with scores ranging from 4 to 8. Nine studies were considered of moderate quality, including one that scored 4 and eight that scored 5, while 15 studies were categorized as high quality, with PEDro scores of 6 or higher (Maher et al., 2003).
○ The level of evidence was considered as very limited when pooled results were not statistically significant and came from multiple studies that were statistically heterogeneous.

## Results

### 1. Overall effect

The flow diagram of the search process is illustrated in Figure 1. The literature search led to the identification of 2669 potential studies eligible for inclusion in our analysis. Over 2000 (2172) articles were screened after removing duplicates, and 40 were assessed for eligibility. Thirteen studies (Barwood et al., 2017; Bonde-Petersen et al., 1992; Damijan and Uhrynski, 2012; Fox et al., 2003; Gregson et al., 2011; Hayward, 1984; Hayward and Eckerson, 1984; O'Brien et al., 2000; Tipton et al., 2000, 1998; Tipton and Golden, 1987; Versteeg et al., 2023; Zhang et al., 2003) were excluded from our analysis. The reasons for exclusion of each study are detailed in Appendix 1 (Supplementary material (SM)). Twenty-seven articles were included in our systematic review. Among them, 3 studies (Mawhinney et al., 2020; Westerlund et al., 2006, 2004) were excluded from the meta-analysis and meta-regression owing to the unavailability of relevant data. Finally, 24 articles were included in the meta-analysis and meta-regression. No additional articles were manually identified by examining the reference lists of the articles included.

A summary of the included studies is presented in Table 1. Additionally, the results of individual studies and pooled effect size are graphically displayed in forest plots (Appendix 2, see SM). Funnel plots used to identify a possible publication bias are presented in Appendix 3 (see SM). Symmetrical distribution of all measures around the mean effect size indicates that the sampling error was random. The results of leave-one-out sensitivity analysis showed that the estimated effect of cold exposure on all cardiovascular and autonomic nervous system variables is robust and not driven by any single study (Appendix 4, see SM). The PEDro scores obtained from each included study are presented in Table 2. The methodological quality average was 6.00 ± 1.06, with scores ranging from 4 to 8. Nine studies were considered of moderate quality, including one that scored 4 and eight that scored 5, while 15 studies were categorized as high quality, with PEDro scores of 6 or higher (Maher et al., 2003).
<figure><img src="image_1.png" /><figcaption>**Figure 1.** Flowchart of the study selection process.</figcaption></figure>

MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; HR: Heart rate; RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low/high frequency power; EXP.G: Experimental Groups
<figure><img src="image_2.png" /><figcaption>**Figure 1.** Flowchart of the study selection process.</figcaption></figure>

MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; HR: Heart rate; RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low/high frequency power; EXP.G: Experimental Groups
<table><caption>Table 1. Summary of the included studies investigating the impact of cold exposure on cardiovascular and cardiac autonomic control responses.</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Study design</th><th colspan="3">Participant characteristics</th><th colspan="3">Cold exposure characteristics</th><th rowspan="2">Main Outcomes</th></tr><tr><th>Sex</th><th>Age (years)</th><th>BMI (Kg/m²)</th><th>Physical level</th><th>Type</th><th>Temperature (°C)</th><th>Duration (min)</th></tr></thead><tbody><tr><td>Theurot et al., 2021</td><td>• RCCT</td><td>• Men (n=9)<br>• Women (n=9)</td><td>• 22.3 ± 1.8<br>• 22.8 ± 1.4</td><td>• 24.6 ± 2.5<br>• 21.8 ± 2.3</td><td>Physically active</td><td>PBC</td><td>-150</td><td>3</td><td>• ↗ HR, LF, and LF/HF ratio after PBC in men and women.<br>• ↗ RMSSD and HF after PBC in men and women.</td></tr><tr><td>Hausswirth et al., 2013</td><td>• nRCT</td><td>• Men</td><td>• 34.6 ± 11.5<br>• 33.3 ± 13.8</td><td>• 24.2 ± 3.0<br>• 25.0 ± 3.3</td><td>NA</td><td>• PBC (n=15)<br>• WBC (n=15)</td><td>-160<br>-110</td><td>3</td><td>• ↗ HR after WBC and PBC (WBC > PBC)<br>• ↗ RMSSD and HF after PBC and WBC (WBC ≈ PBC)<br>• ↗ SAP and DAP after WBC.<br>• ↗ T°sk for all body regions immediately after WBC and PBC exposure, persisting up to 20 min after the session.<br>• ↗ T°tm only after WBC exposure.</td></tr><tr><td>Hammond et al., 2020</td><td>• nRCCT</td><td>• Men (n=9)<br>• Women (n=8)</td><td>• 23.1 ± 3.4<br>• 26.0 ± 7.0</td><td>25.9 ± 2.3<br>23.3 ± 2.7</td><td>Physically active</td><td>WBC</td><td>-140</td><td>3</td><td>• → HR and DAP after WBC in men and women<br>• ↗ SAP after WBC in men and women<br>• Men ≈ women for HR SAP and DAP after WBC.</td></tr><tr><td>Louis et al., 2015</td><td>• RCT</td><td>• Men</td><td>• 34.7 ± 11.5<br>• 34.8 ± 9.1</td><td>• 24.2 ± 3.0<br>• 25 ± 5.8</td><td>Physically active</td><td>• PBC (n=10)<br>• WBC (n=10)</td><td>-160<br>-60</td><td>3</td><td>• ↗ HR after WBC and PBC (WBC > PBC)<br>• ↗ RMSSD and HF after PBC and WBC (WBC ≈ PBC)<br>• → SAP and DAP after WBC and PBC</td></tr></tbody></table>
<table><caption>Table 1. Summary of the included studies investigating the impact of cold exposure on cardiovascular and cardiac autonomic control responses.</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Study design</th><th colspan="3">Participant characteristics</th><th colspan="3">Cold exposure characteristics</th><th rowspan="2">Main Outcomes</th></tr><tr><th>Sex</th><th>Age (years)</th><th>BMI (Kg/m²)</th><th>Physical level</th><th>Type</th><th>Temperature (°C)</th><th>Duration (min)</th></tr></thead><tbody><tr><td>Theurot et al., 2021</td><td>• RCCT</td><td>• Men (n=9)<br/>• Women (n=9)</td><td>• 22.3 ± 1.8<br/>• 22.8 ± 1.4</td><td>• 24.6 ± 2.5<br/>• 21.8 ± 2.3</td><td>Physically active</td><td>PBC</td><td>-150</td><td>3</td><td>• ↗ HR, LF, and LF/HF ratio after PBC in men and women.<br/>• ↗ RMSSD and HF after PBC in men and women.</td></tr><tr><td>Hausswirth et al., 2013</td><td>• nRCT</td><td>• Men</td><td>• 34.6 ± 11.5<br/>• 33.3 ± 13.8</td><td>• 24.2 ± 3.0<br/>• 25.0 ± 3.3</td><td>NA</td><td>• PBC (n=15)<br/>• WBC (n=15)</td><td>-160<br/>-110</td><td>3</td><td>• ↗ HR after WBC and PBC (WBC > PBC)<br/>• ↗ RMSSD and HF after PBC and WBC (WBC ≈ PBC)<br/>• ↗ SAP and DAP after WBC.<br/>• ↗ T°sk for all body regions immediately after WBC and PBC exposure, persisting up to 20 min after the session.<br/>• ↗ T°tm only after WBC exposure.</td></tr><tr><td>Hammond et al., 2020</td><td>• nRCCT</td><td>• Men (n=9)<br/>• Women (n=8)</td><td>• 23.1 ± 3.4<br/>• 26.0 ± 7.0</td><td>25.9 ± 2.3<br/>23.3 ± 2.7</td><td>Physically active</td><td>WBC</td><td>-140</td><td>3</td><td>• → HR and DAP after WBC in men and women<br/>• ↗ SAP after WBC in men and women<br/>• Men ≈ women for HR SAP and DAP after WBC.</td></tr><tr><td>Louis et al., 2015</td><td>• RCT</td><td>• Men</td><td>• 34.7 ± 11.5<br/>• 34.8 ± 9.1</td><td>• 24.2 ± 3.0<br/>• 25 ± 5.8</td><td>Physically active</td><td>• PBC (n=10)<br/>• WBC (n=10)</td><td>-160<br/>-60</td><td>3</td><td>• ↗ HR after WBC and PBC (WBC > PBC)<br/>• ↗ RMSSD and HF after PBC and WBC (WBC ≈ PBC)<br/>• → SAP and DAP after WBC and PBC</td></tr></tbody></table>
<table><tr><td>Dębiec-Bak<br>et al., 2013</td><td>• E P-P</td><td>Mixed group<br>• Men (n=103)<br>• Women<br>(n=137)</td><td>• 22.74 ±<br>0.99<br>• 22.86 ±<br>0.94</td><td>NA</td><td>NA</td><td>WBC</td><td>-60<br>-60<br>-100<br>-100<br>-120<br>-120<br>-140<br>-140</td><td>1<br>3<br>1<br>3<br>1<br>3<br>1<br>3</td><td>• ↗ T°sk for all body regions immediately after WBC and PBC exposure, persisting up to 20 min after cold exposure.<br>• ↗ Ttm° after WBC and PBC exposure (WBC > PBC).</td></tr><tr><td>Cuttell et<br>al., 2017</td><td>• E P-P</td><td>• Men (n=10)<br>• Women<br>(n=8)</td><td>• 27.7 ± 6.9<br>• 27.6 ± 6.3</td><td>• 23.6 ± 2.4<br>• 23.2 ± 2.8</td><td>Untrained</td><td>WBC</td><td>-110</td><td>3</td><td>• ↗ SAP, and DAP in all examined subgroups.<br>• All measured values remained in physiological range.<br>• ↗ T°sk for all body regions immediately after WBC (Lower limbs > other body area).<br>• The lowest cooling temperatures (120 and 140 °C) and longer exposure time (3 min) caused the greater ↗ in T°sk</td></tr><tr><td>Fonda et<br>al., 2014</td><td>• RnCCT</td><td>• Men (n=12)</td><td>• 23.9 ± 4.2</td><td>• 21.5 ± 2.1</td><td>NA</td><td>WBC</td><td>-140</td><td>1.5<br>2<br>2.5<br>3</td><td>• ↗ HR in men and women over time until 35 min after WBC (Men ≈ women).<br>• ↗ MAP in men and women over time until 35 min after WBC (Men > women)<br>• ↗ T°c in men and women after 35 min of WBC<br>• ↗ T°sk in men and women immediately, 5 min and 10 min after WBC (Women> men)<br>• ↗ Ttm in men and women after WBC<br>• → HR, SAP, and DAP after all WBC exposure durations<br>• ↗ T°sk for all body regions immediately after WBC<br>• T°sk significantly lower after longer exposure ( 2.5 min and 3 min)</td></tr></table>
<table><tr><td>Dębiec-Bak<br>et al., 2013</td><td>• E P-P</td><td>Mixed group<br>• Men (n=103)<br>• Women<br>(n=137)</td><td>• 22.74 ±<br>0.99<br>• 22.86 ±<br>0.94</td><td>NA</td><td>NA</td><td>WBC</td><td>-60<br>-60<br>-100<br>-100<br>-120<br>-120<br>-140<br>-140</td><td>1<br>3<br>1<br>3<br>1<br>3<br>1<br>3</td><td>• ↗ T°sk for all body regions immediately after WBC and PBC exposure, persisting up to 20 min after cold exposure.<br>• ↗ Ttm° after WBC and PBC exposure (WBC > PBC).</td></tr><tr><td>Cuttell et<br>al., 2017</td><td>• E P-P</td><td>• Men (n=10)<br>• Women<br>(n=8)</td><td>• 27.7 ± 6.9<br>• 27.6 ± 6.3</td><td>• 23.6 ± 2.4<br>• 23.2 ± 2.8</td><td>Untrained</td><td>WBC</td><td>-110</td><td>3</td><td>• ↗ SAP, and DAP in all examined subgroups.<br>• All measured values remained in physiological range.<br>• ↗ T°sk for all body regions immediately after WBC (Lower limbs > other body area).<br>• The lowest cooling temperatures (120 and 140 °C) and longer exposure time (3 min) caused the greater ↗ in T°sk</td></tr><tr><td>Fonda et<br>al., 2014</td><td>• RnCCT</td><td>• Men (n=12)</td><td>• 23.9 ± 4.2</td><td>• 21.5 ± 2.1</td><td>NA</td><td>WBC</td><td>-140</td><td>1.5<br>2<br>2.5<br>3</td><td>• ↗ HR in men and women over time until 35 min after WBC (Men ≈ women).<br>• ↗ MAP in men and women over time until 35 min after WBC (Men > women)<br>• ↗ T°c in men and women after 35 min of WBC<br>• ↗ T°sk in men and women immediately, 5 min and 10 min after WBC (Women> men)<br>• ↗ Ttm in men and women after WBC<br>• → HR, SAP, and DAP after all WBC exposure durations<br>• ↗ T°sk for all body regions immediately after WBC<br>• T°sk significantly lower after longer exposure ( 2.5 min and 3 min)</td></tr></table>
<table><tr><td>Zalewski et al., 2014a</td><td>• E P-P</td><td>• Men (n=25)</td><td>• 30.1 ± 3.7</td><td>• 25.9 ± 2.8</td><td>NA</td><td>WBC</td><td>-120</td><td>3</td><td>• ↗ HR after WBC<br>• → MAP, SAP, and DAP after WB<br>• ↗ LF and HF after WBC then ↗ at WBC + 3h and WBC + 6h<br>• ↗ LF/HF ratio after WBC then ↗ at WBC + 3h and WBC + 6h<br>• ↗ T°C 50-60 min following WBC.</td></tr><tr><td>Zalewski et al., 2013</td><td>• E P-P</td><td>• Men (n=30)</td><td>• 32.8 ± 6.9</td><td>• 25.6 ± 2.9</td><td>NA</td><td>WBC</td><td>-120</td><td>3</td><td>• ↗ HR after WBC then returned to basal values at WBC + 3h and WBC + 6h<br>• → MAP, SAP, and DAP after WBC</td></tr><tr><td>Lubkowska and Suska, 2011</td><td>• E P-P</td><td>• Men (n=40)</td><td>• 22.0 ± 0.7</td><td>• 22.3 ± 2.93</td><td>NA</td><td>WBC</td><td>-130</td><td>3</td><td>• ↗ MAP, SAP, and DAP after WBC then returned to basal values at WBC + 10 min and WBC + 20 min.<br>• ↗ HR after WBC then returned to basal values at WBC + 10 min and WBC + 20 min.</td></tr><tr><td>Lubkowska and Szyguła, 2010</td><td>• E P-P</td><td>• Men (n=25)</td><td>• 21.3 ± 0.94</td><td>• 23.19 ± 1.9</td><td>Physically active</td><td>WBC</td><td>-130</td><td>3</td><td>• ↗ MAP, SAP, and DAP after WBC then returned to basal values at WBC + 10 min.<br>• ↗ HR after WBC then returned to basal values at WBC + 10 min.<br>• → HR, MAP, SAP, and DAP after 15 sessions of WBC.</td></tr><tr><td>Louis et al., 2020</td><td>• RCT</td><td>• Men (n=40)</td><td>• 21.3 ± 0.94</td><td>• 23.19 ± 1.9</td><td>Physically active</td><td>WBC</td><td>-60<br>-110</td><td>3</td><td>• ↗ HR after WBC at -60 °C and at -110 °C.<br>• ↗ SAP and SAP only after WBC at -110 °C.<br>• ↗ RMSSD after WBC at -60 °C and at -110 °C.<br>• ↗ HF only after WBC at -110 °C.<br>• ↗ LF/HF ratio after WBC at -60 °C and at -110 °C.</td></tr></table>
<table><tr><td>Zalewski et al., 2014a</td><td>• E P-P</td><td>• Men (n=25)</td><td>• 30.1 ± 3.7</td><td>• 25.9 ± 2.8</td><td>NA</td><td>WBC</td><td>-120</td><td>3</td><td>• ↗ HR after WBC<br>• → MAP, SAP, and DAP after WB<br>• ↗ LF and HF after WBC then ↗ at WBC + 3h and WBC + 6h<br>• ↗ LF/HF ratio after WBC then ↗ at WBC + 3h and WBC + 6h<br>• ↗ T°C 50-60 min following WBC.</td></tr><tr><td>Zalewski et al., 2013</td><td>• E P-P</td><td>• Men (n=30)</td><td>• 32.8 ± 6.9</td><td>• 25.6 ± 2.9</td><td>NA</td><td>WBC</td><td>-120</td><td>3</td><td>• ↗ HR after WBC then returned to basal values at WBC + 3h and WBC + 6h<br>• → MAP, SAP, and DAP after WBC</td></tr><tr><td>Lubkowska and Suska, 2011</td><td>• E P-P</td><td>• Men (n=40)</td><td>• 22.0 ± 0.7</td><td>• 22.3 ± 2.93</td><td>NA</td><td>WBC</td><td>-130</td><td>3</td><td>• ↗ MAP, SAP, and DAP after WBC then returned to basal values at WBC + 10 min and WBC + 20 min.<br>• ↗ HR after WBC then returned to basal values at WBC + 10 min and WBC + 20 min.</td></tr><tr><td>Lubkowska and Szyguła, 2010</td><td>• E P-P</td><td>• Men (n=25)</td><td>• 21.3 ± 0.94</td><td>• 23.19 ± 1.9</td><td>Physically active</td><td>WBC</td><td>-130</td><td>3</td><td>• ↗ MAP, SAP, and DAP after WBC then returned to basal values at WBC + 10 min.<br>• ↗ HR after WBC then returned to basal values at WBC + 10 min.<br>• → HR, MAP, SAP, and DAP after 15 sessions of WBC.</td></tr><tr><td>Louis et al., 2020</td><td>• RCT</td><td>• Men (n=40)</td><td>• 21.3 ± 0.94</td><td>• 23.19 ± 1.9</td><td>Physically active</td><td>WBC</td><td>-60<br>-110</td><td>3</td><td>• ↗ HR after WBC at -60 °C and at -110 °C.<br>• ↗ SAP and SAP only after WBC at -110 °C.<br>• ↗ RMSSD after WBC at -60 °C and at -110 °C.<br>• ↗ HF only after WBC at -110 °C.<br>• ↗ LF/HF ratio after WBC at -60 °C and at -110 °C.</td></tr></table>
<table><tr><td>Coppi et al., 2022</td><td>•E P-P</td><td>• Men (n=10)</td><td>• 38.0 ± 12.0</td><td>• 19.5 ± 2.0</td><td>Physically active</td><td>WBC</td><td>NA</td><td>3</td><td>• ↗ Tsk° immediately after WBC (-110°C > -60°C), persisting up to 20 min after exposure (only at -110°C)<br/>• ↗ T°tm until 20 min after WBC (-110°C > -60°C)</td></tr><tr><td>Westerlund et al., 2004</td><td>•E P-P</td><td>• Women (n=10)</td><td>• 38 ± 3</td><td>• 24 ± 3</td><td>Sedentary</td><td>WBC</td><td>-60<br/>-110</td><td>2</td><td>• ↗ SAP after WBC (-110°C > -60 °C)<br/>• ↗ DAP after WBC (-110°C > -60 °C)</td></tr><tr><td>Westerlund et al., 2006</td><td>•E P-P</td><td>• Women (n=10)</td><td>• 38 ± 3</td><td>• 24 ± 3</td><td>Moderately physically active</td><td>WBC</td><td>-60<br/>-110</td><td>2</td><td>• ↗ RR, RMSSD and HF after CWI<br/>• ↗ HF and LF/HF ratio after CWI</td></tr><tr><td>Rose et al., 2023</td><td>•RCT</td><td>• Men</td><td>• 23.4 ± 4.6</td><td>• 24.4 ± NA</td><td>NA</td><td>• PBC (n=8)<br/>• Head-out CWI (n=9)</td><td>• -110 to -140 °C<br/>9 °C</td><td>3</td><td>• ↗ HR after PBC<br/>• ↗ HR after CWI<br/>• ↗ SAP and DAP after PBC and CWI</td></tr><tr><td>Muller et al., 2012</td><td>•RCCT</td><td>• Men (n=9)</td><td>• 23.0 ± 2.0</td><td>• 25.9 ± NA</td><td>NA</td><td>Lower body CWI</td><td>13</td><td>60</td><td>• ↗ SAP at 10 min and 60 of CWI.<br/>• ↗ DAP at 10 min, 40 min, and 60 of CWI.<br/>• ↗ SAP at 10, 40 min, 50 min, and 60 of CWI.<br/>• ↗ HR at 20 min of CWI.<br/>• ↗ Tsk° 15 min, 20 min, 45 min and 60 min of CWI<br/>• ↗ T°re at 60 min of CWI.</td></tr><tr><td>Sramek et al., 2000</td><td>•RCCT</td><td>• Men (n=10)</td><td>• 22.2 ± 2.4</td><td>NA</td><td>NA</td><td>Head-out CWI</td><td>14</td><td>60</td><td>• ↗ HR, SAP, and DAP after CWI<br/>• ↗ T°re after CWI.</td></tr><tr><td>Eimonte et al., 2021</td><td>•CRCT</td><td>• Men (n=12)</td><td>• 23.0 ± 4.0</td><td>• 23.67 ± 1.85</td><td>Physically active</td><td>Head-out CWI</td><td>14</td><td>10</td><td>• ↗ HR after CWI<br/>• ↗ Tsk° immediately after CWI persisting up to 1h.<br/>• ↗ T°re from 45 to 70 min after CWI</td></tr></table>
<table><tr><td>Coppi et al., 2022</td><td>•E P-P</td><td>• Men (n=10)</td><td>• 38.0 ± 12.0</td><td>• 19.5 ± 2.0</td><td>Physically active</td><td>WBC</td><td>NA</td><td>3</td><td>• ↗ Tsk° immediately after WBC (-110°C > -60°C), persisting up to 20 min after exposure (only at -110°C)<br/>• ↗ T°tm until 20 min after WBC (-110°C > -60°C)</td></tr><tr><td>Westerlund et al., 2004</td><td>•E P-P</td><td>• Women (n=10)</td><td>• 38 ± 3</td><td>• 24 ± 3</td><td>Sedentary</td><td>WBC</td><td>-60<br/>-110</td><td>2</td><td>• ↗ SAP after WBC (-110°C > -60 °C)<br/>• ↗ DAP after WBC (-110°C ≈ -60 °C)</td></tr><tr><td>Westerlund et al., 2006</td><td>•E P-P</td><td>• Women (n=10)</td><td>• 38 ± 3</td><td>• 24 ± 3</td><td>Moderately physically active</td><td>WBC</td><td>-60<br/>-110</td><td>2</td><td>• ↗ RR, RMSSD and HF after CWI<br/>• ↗ HF and LF/HF ratio after CWI</td></tr><tr><td>Rose et al., 2023</td><td>•RCT</td><td>• Men</td><td>• 23.4 ± 4.6</td><td>• 24.4 ± NA</td><td>NA</td><td>• PBC (n=8)<br/>• Head-out CWI (n=9)</td><td>• -110 to -140 °C<br/>9 °C</td><td>3</td><td>• ↗ HR after PBC<br/>• ↗ HR after CWI<br/>• ↗ SAP and DAP after PBC and CWI</td></tr><tr><td>Muller et al., 2012</td><td>•RCCT</td><td>• Men (n=9)</td><td>• 23.0 ± 2.0</td><td>• 25.9 ± NA</td><td>NA</td><td>Lower body CWI</td><td>13</td><td>60</td><td>• ↗ SAP at 10 min and 60 of CWI.<br/>• ↗ DAP at 10 min, 40 min, and 60 of CWI.<br/>• ↗ SAP at 10, 40 min, 50 min, and 60 of CWI.<br/>• ↗ HR at 20 min of CWI.<br/>• ↗ Tsk° 15 min, 20 min, 45 min and 60 min of CWI<br/>• ↗ T°re at 60 min of CWI.</td></tr><tr><td>Sramek et al., 2000</td><td>•RCCT</td><td>• Men (n=10)</td><td>• 22.2 ± 2.4</td><td>NA</td><td>NA</td><td>Head-out CWI</td><td>14</td><td>60</td><td>• ↗ HR, SAP, and DAP after CWI<br/>• ↗ T°re after CWI.</td></tr><tr><td>Eimonte et al., 2021</td><td>•CRCT</td><td>• Men (n=12)</td><td>• 23.0 ± 4.0</td><td>• 23.67 ± 1.85</td><td>Physically active</td><td>Head-out CWI</td><td>14</td><td>10</td><td>• ↗ HR after CWI<br/>• ↗ Tsk° immediately after CWI persisting up to 1h.<br/>• ↗ T°re from 45 to 70 min after CWI</td></tr></table>
<table><tr><td>Vogelaere et al., 1995</td><td>•E P-P</td><td>• Men (n=15)</td><td>• 31.2 ± 2.3</td><td>• 22.2 ± NA</td><td>NA</td><td>Head-out CWI</td><td>15</td><td>60</td><td>• ↗ HR at 5 min and 10 min of CWI.<br>• ↗ HR at 20 min of CWI.<br>• →T°re during CWI<br>• ↗ Tsk° from 2 to 60 min following CWI</td></tr><tr><td>Jansky et al., 1996</td><td>•E P-P</td><td>• Men (n=10)</td><td>• 22.5 ± 1.8</td><td>NA</td><td>Physically active</td><td>Head-out CWI</td><td>14</td><td>60</td><td>• → HR after the 1<sup>st</sup> and the 18<sup>th</sup> sessions of CWI.<br>• ↗ SAP and DAP after CWI<br>• ↗ SAP and DAP after 18<sup>th</sup> session of CWI compared to the 1<sup>st</sup> session.<br>• ↗ T°sk during CWI</td></tr><tr><td>Kwiecien et al., 2019</td><td>•E P-P</td><td>• Men (n=11)</td><td>• 27.0 ± 7.0</td><td>• 24.2 ± NA</td><td>Physically active</td><td>Lower body CWI</td><td>15</td><td>15</td><td>• ↗ HR after CWI.<br>• ↗ RMSSD after CWI<br>• → SAP and DAP after CWI<br>• ↗ T°sk and T°c during CWI</td></tr><tr><td>Mantoni et al., 2007</td><td>•E P-P</td><td>• Men (n=13)</td><td>• 32.0 ± 7.0</td><td>• 25.4 ± NA</td><td>NA</td><td>Head-out CWI</td><td>0</td><td>0.5</td><td>• ↗ HR after CWI.</td></tr><tr><td>Barwood et al., 2014</td><td>•E P-P</td><td>Mixed group<br>• Men (n=8)<br>• Women (n=4)</td><td>• 20.0 ± 1.0</td><td>• 23.8 ± NA</td><td>NA</td><td>Head-out CWI</td><td>15</td><td>7</td><td>• ↗ HR after CWI.</td></tr><tr><td>Mantoni et al., 2008</td><td>•E P-P</td><td>Mixed group<br>• Men (n=5)<br>• Women (n=4)</td><td>• 29.0 ± 10.2</td><td>NA</td><td>NA</td><td>Head-out CWI</td><td>0</td><td>1</td><td>• ↗ HR after CWI.</td></tr><tr><td>Brazaitis et al., 2014</td><td>•E P-P</td><td>• Men (n=14)</td><td>• 21.6 ± 0.5</td><td>• 20.7 ± 1.3</td><td>Physically active</td><td>Head-out CWI</td><td>14</td><td>Until the T°re reached 35.5 °C or 170 min had elapsed</td><td>• ↗ HR after CWI.<br>• ↗ HR after 17<sup>th</sup> session of CWI compared to the 1<sup>st</sup> session.<br>• ↗ T°sk and T°re after CWI</td></tr></table>
<table><tr><td>Vogelaere et al., 1995</td><td>•E P-P</td><td>•Men (n=15)</td><td>•31.2 ± 2.3</td><td>•22.2 ± NA</td><td>NA</td><td>Head-out CWI</td><td>15</td><td>60</td><td>• ↗ HR at 5 min and 10 min of CWI.<br>• ↗ HR at 20 min of CWI.<br>• →T°re during CWI<br>• ↗ Tsk° from 2 to 60 min following CWI</td></tr><tr><td>Jansky et al., 1996</td><td>•E P-P</td><td>•Men (n=10)</td><td>•22.5 ± 1.8</td><td>NA</td><td>Physically active</td><td>Head-out CWI</td><td>14</td><td>60</td><td>• → HR after the 1<sup>st</sup> and the 18<sup>th</sup> sessions of CWI.<br>• ↗ SAP and DAP after CWI<br>• ↗ SAP and DAP after 18<sup>th</sup> session of CWI compared to the 1<sup>st</sup> session.<br>• ↗ T°sk during CWI</td></tr><tr><td>Kwiecien et al., 2019</td><td>•E P-P</td><td>•Men (n=11)</td><td>•27.0 ± 7.0</td><td>•24.2 ± NA</td><td>Physically active</td><td>Lower body CWI</td><td>15</td><td>15</td><td>• ↗ HR after CWI.<br>• ↗ RMSSD after CWI<br>• → SAP and DAP after CWI<br>• ↗ T°sk and T°c during CWI</td></tr><tr><td>Mantoni et al., 2007</td><td>•E P-P</td><td>•Men (n=13)</td><td>•32.0 ± 7.0</td><td>•25.4 ± NA</td><td>NA</td><td>Head-out CWI</td><td>0</td><td>0.5</td><td>• ↗ HR after CWI.</td></tr><tr><td>Barwood et al., 2014</td><td>•E P-P</td><td>Mixed group<br>•Men (n=8)<br>•Women (n=4)</td><td>•20.0 ± 1.0</td><td>•23.8 ± NA</td><td>NA</td><td>Head-out CWI</td><td>15</td><td>7</td><td>• ↗ HR after CWI.</td></tr><tr><td>Mantoni et al., 2008</td><td>•E P-P</td><td>Mixed group<br>•Men (n=5)<br>•Women (n=4)</td><td>•29.0 ± 10.2</td><td>NA</td><td>NA</td><td>Head-out CWI</td><td>0</td><td>1</td><td>• ↗ HR after CWI.</td></tr><tr><td>Brazaitis et al., 2014</td><td>•E P-P</td><td>•Men (n=14)</td><td>•21.6 ± 0.5</td><td>•20.7 ± 1.3</td><td>Physically active</td><td>Head-out CWI</td><td>14</td><td>Until the T°re reached 35.5 °C or 170 min had elapsed</td><td>• ↗ HR after CWI.<br>• ↗ HR after 17<sup>th</sup> session of CWI compared to the 1<sup>st</sup> session.<br>• ↗ T°sk and T°re after CWI</td></tr></table>
<table><tr><td>Mawhinney et al., 2020</td><td>•E P-P</td><td>•Men</td><td>•33 ± 8</td><td>•24.2 ± NA</td><td>Physically active</td><td>Lower body CWI</td><td>•8 °C (n=10)<br/>•15°C (n=10)</td><td>•10</td><td>• No significant difference was observed between conditions for HR and MAP (8 °C ≈ 15°C)<br/>• T°sk after CWI (8°C)<br/>• Thigh skin temperature after CWI (8°C and 15°C)</td></tr></table>

Decrease: Decrease; Increase: Increase; no change: Greater effect; equal effect: n = sample size; BMI: body mass index; PBC: Partial body cryostimulation; WBC: Whole body cryostimulation; CWI: cold water immersion; HR: Heart rate; RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low-high frequency power; MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; T°sk: Skin temperature; T°tm: Tympanic temperature, T°c: core temperature; RCCT: Randomized controlled crossover trial; nRCT: non-randomized controlled crossover trial; RnCCT: Randomized non-controlled crossover trial; nRCT: non-randomized controlled trial; RCT: Randomized control trial; E P-P: Experimental pre-post design; T°re: Rectal temperature.
<table><tr><td>Mawhinney et al., 2020</td><td>•E P-P</td><td>•Men</td><td>•33 ± 8</td><td>•24.2 ± NA</td><td>Physically active</td><td>Lower body CWI</td><td>•8 °C (n=10)<br/>•15°C (n=10)</td><td>•10</td><td>• No significant difference was observed between conditions for HR and MAP (8 °C ≈ 15°C)<br/>• T°sk after CWI (8°C)<br/>• Thigh skin temperature after CWI (8°C and 15°C)</td></tr></table>

Decrease: Decrease; Increase: Increase; no change: no change; Greater effect: Greater effect; Equal effect: Equal effect; n = sample size; BMI: body mass index; PBC: Partial body cryostimulation; WBC: Whole body cryostimulation; CWI: cold water immersion; HR: Heart rate; RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low-high frequency power; MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; T°sk: Skin temperature; T°tm: Tympanic temperature, T°c: core temperature; RCCT: Randomized controlled crossover trial; nRCT: non-randomized controlled crossover trial; RnCCT: Randomized non-controlled crossover trial; nRCT: non-randomized controlled trial; RCT: Randomized control trial; E P-P: Experimental pre-post design; T°re: Rectal temperature.
<table><caption>**Table 2.** Methodological quality of included studies.</caption><thead><tr><th rowspan="2">Study</th><th colspan="11">Item</th><th rowspan="2">PEDro Score</th><th rowspan="2">Quality</th></tr><tr><th>1</th><th>2</th><th>3</th><th>4</th><th>5</th><th>6</th><th>7</th><th>8</th><th>9</th><th>10</th><th>11</th></tr></thead><tbody><tr><td>Theurot et al., 2021</td><td>1</td><td>1</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>8</td><td>High</td></tr><tr><td>Hausswirth et al., 2013</td><td>1</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Hammond et al., 2020</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Louis et al., 2015</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Dębiec-Bąk et al., 2013</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Cuttell et al., 2017</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Fonda et al., 2014</td><td>0</td><td>1</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Zalewski et al., 2014a</td><td>1</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Zalewski et al., 2013</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Lubkowska and Suska, 2011</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Lubkowska and Szyguła, 2010</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Louis et al., 2020</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Coppi et al., 2022</td><td>1</td><td>0</td><td>0</td><td>0</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>0</td><td>1</td><td>4</td><td>Medium</td></tr><tr><td>Rose et al., 2023</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Muller et al., 2012</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Sramek et al., 2000</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Eimonte et al., 2021</td><td>1</td><td>1</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>8</td><td>High</td></tr><tr><td>Vogelaere et al., 1995</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Jansky et al., 1996</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Kwiecien et al., 2019</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Mantoni et al., 2007</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Barwood et al., 2014</td><td>1</td><td>0</td><td>0</td><td>1</td><td>1</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Mantoni et al., 2008</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Brazaitis et al., 2014</td><td>1</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr></tbody></table>

## 2. Cardiovascular responses

The overall SMD shows that cold exposure (cryostimulation and CWI) induces a significant change in cardiovascular outcomes (Table 3). In fact, pooled data showed significantly decreased HR following exposure, with a small negative effect (SMD = -0.16; 95% CI: -0.04 to -0.28; z = -2.55; I² = 39.90; **p = 0.011**) and slightly increased MAP (SMD = 0.28; 95% CI: 0.17 to 0.40; z = -4.94; I² = 20.12; **p = 0.000**); in SAP (SMD = 0.37; 95% CI: 0.24 to 0.51; z = 5.36; I² = 27.03; **p = 0.000**); and in DAP (SMD = 0.40; 95% CI: 0.29 to 0.52; z = 6.70; I² = 19.23; **p = 0.000**). Statistical heterogeneity justified a subgroup analysis with moderator variables, including individual characteristics, as well as cold exposure interventions and cooled body area.
<table><caption>**Table 2.** Methodological quality of included studies.</caption><thead><tr><th rowspan="2">Study</th><th colspan="11">Item</th><th rowspan="2">PEDro Score</th><th rowspan="2">Quality</th></tr><tr><th>1</th><th>2</th><th>3</th><th>4</th><th>5</th><th>6</th><th>7</th><th>8</th><th>9</th><th>10</th><th>11</th></tr></thead><tbody><tr><td>Theurot et al., 2021</td><td>1</td><td>1</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>8</td><td>High</td></tr><tr><td>Hausswirth et al., 2013</td><td>1</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Hammond et al., 2020</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Louis et al., 2015</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Dębiec-Bąk et al., 2013</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Cuttell et al., 2017</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Fonda et al., 2014</td><td>0</td><td>1</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Zalewski et al., 2014a</td><td>1</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Zalewski et al., 2013</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Lubkowska and Suska, 2011</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Lubkowska and Szyguła, 2010</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Louis et al., 2020</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Coppi et al., 2022</td><td>1</td><td>0</td><td>0</td><td>0</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>0</td><td>1</td><td>4</td><td>Medium</td></tr><tr><td>Rose et al., 2023</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Muller et al., 2012</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Sramek et al., 2000</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr><tr><td>Eimonte et al., 2021</td><td>1</td><td>1</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>8</td><td>High</td></tr><tr><td>Vogelaere et al., 1995</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Jansky et al., 1996</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Kwiecien et al., 2019</td><td>1</td><td>1</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Mantoni et al., 2007</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Barwood et al., 2014</td><td>1</td><td>0</td><td>0</td><td>1</td><td>1</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>7</td><td>High</td></tr><tr><td>Mantoni et al., 2008</td><td>0</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>5</td><td>Medium</td></tr><tr><td>Brazaitis et al., 2014</td><td>1</td><td>0</td><td>0</td><td>1</td><td>0</td><td>0</td><td>0</td><td>1</td><td>1</td><td>1</td><td>1</td><td>6</td><td>High</td></tr></tbody></table>

## 2. Cardiovascular responses

The overall SMD shows that cold exposure (cryostimulation and CWI) induces a significant change in cardiovascular outcomes (Table 3). In fact, pooled data showed significantly decreased HR following exposure, with a small negative effect (SMD = -0.16; 95% CI: -0.04 to -0.28; z = -2.55; I² = 39.90; **p = 0.011**) and slightly increased MAP (SMD = 0.28; 95% CI: 0.17 to 0.40; z = -4.94; I² = 20.12; **p = 0.000**); in SAP (SMD = 0.37; 95% CI: 0.24 to 0.51; z = 5.36; I² = 27.03; **p = 0.000**); and in DAP (SMD = 0.40; 95% CI: 0.29 to 0.52; z = 6.70; I² = 19.23; **p = 0.000**). Statistical heterogeneity justified a subgroup analysis with moderator variables, including individual characteristics, as well as cold exposure interventions and cooled body area.
<table><caption>Table 3. Overall effects of cold exposure on cardiovascular responses</caption><thead><tr><th></th><th>Participants<br>(s)</th><th>Experimental<br>groups (n)</th><th>Level of<br>evidence</th><th>SMD</th><th>CI 95 %</th><th>p</th></tr></thead><tbody><tr><td>HR</td><td>1234</td><td>93</td><td>Strong</td><td>-0.16</td><td>-0.04; -0.28</td><td><strong>0.011</strong></td></tr><tr><td>MAP</td><td>1210</td><td>78</td><td>Strong</td><td>0.28</td><td>0.17; 0.40</td><td><strong>0.000</strong></td></tr><tr><td>SAP</td><td>1066</td><td>62</td><td>Strong</td><td>0.37</td><td>0.24; 0.51</td><td><strong>0.000</strong></td></tr><tr><td>DAP</td><td>1066</td><td>62</td><td>Strong</td><td>0.40</td><td>0.29; 0.52</td><td><strong>0.000</strong></td></tr></tbody></table>

HR: Heart rate; MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; SMD: Standardized mean difference; CI: confidence interval.

## 2.1. Heart rate

Our results indicate that exposure to cold significantly decreases HR in men (SMD= -0.17; **p = 0.011**) and normal-weight participants (SMD = -0.13; **p = 0.031**). Nevertheless, no significant difference between male and female participants or between different BMI categories was observed. Similarly, the meta-regression analysis did not show any significant effect of sex, BMI, body fat percentage, or age on HR changes. Additionally, our findings showed that cryostimulation induces a greater reduction in HR compared to CWI (**p = 0.024**), and that PBC leads to a greater decrease in HR compared to WBC (**p = 0.000**). This finding was supported by the meta-regression analysis, which highlighted a significant impact of cooling technique (CWI: coefficient = 0.35; 95% CI: 0.10 to 0.60; z = 2.73; **p = 0.006**), confirming that cryostimulation has a more substantial effect on HR decrease than CWI. As regards type of cryostimulation, a significant moderating effect (PBC: coefficient = -0.59; 95% CI: -0.92 to -0.25; z = -3.45; **p = 0.001**) was observed, indicating pronounced HR reduction ascribable to PBC intervention.
<table><caption>Table 3. Overall effects of cold exposure on cardiovascular responses</caption><thead><tr><th></th><th>Participants<br>(s)</th><th>Experimental<br>groups (n)</th><th>Level of<br>evidence</th><th>SMD</th><th>CI 95 %</th><th>p</th></tr></thead><tbody><tr><td>HR</td><td>1234</td><td>93</td><td>Strong</td><td>-0.16</td><td>-0.04; -0.28</td><td><strong>0.011</strong></td></tr><tr><td>MAP</td><td>1210</td><td>78</td><td>Strong</td><td>0.28</td><td>0.17; 0.40</td><td><strong>0.000</strong></td></tr><tr><td>SAP</td><td>1066</td><td>62</td><td>Strong</td><td>0.37</td><td>0.24; 0.51</td><td><strong>0.000</strong></td></tr><tr><td>DAP</td><td>1066</td><td>62</td><td>Strong</td><td>0.40</td><td>0.29; 0.52</td><td><strong>0.000</strong></td></tr></tbody></table>

HR: Heart rate; MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; SMD: Standardized mean difference; CI : confidence interval.

## 2.1. Heart rate

Our results indicate that exposure to cold significantly decreases HR in men (SMD= -0.17; **p = 0.011**) and normal-weight participants (SMD = -0.13; p = **0.031**). Nevertheless, no significant difference between male and female participants or between different BMI categories was observed. Similarly, the meta-regression analysis did not show any significant effect of sex, BMI, body fat percentage, or age on HR changes. Additionally, our findings showed that cryostimulation induces a greater reduction in HR compared to CWI (**p = 0.024**), and that PBC leads to a greater decrease in HR compared to WBC (**p = 0.000**). This finding was supported by the meta-regression analysis, which highlighted a significant impact of cooling technique (CWI: coefficient = 0.35; 95% CI: 0.10 to 0.60; z = 2.73; **p = 0.006**), confirming that cryostimulation has a more substantial effect on HR decrease than CWI. As regards type of cryostimulation, a significant moderating effect (PBC: coefficient = -0.59; 95% CI: -0.92 to -0.25; z = -3.45; **p = 0.001**) was observed, indicating pronounced HR reduction ascribable to PBC intervention.
<figure><img src="image_2.png" /><figcaption>**Figure 2.** Effect of cold exposure on heart rate magnitude depending on sex, BMI, cooling technique, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.001.</figcaption></figure>

## 2.2. Arterial pressure

Concerning the impact of cold exposure (cryostimulation and CWI) on arterial pressure, our findings revealed slightly increased MAP (SMD = 0.23; **p = 0.001**) (Figure 3), SAP (SMD = 0.31; **p = 0.000**) (Figure 4) and DAP (SMD = 0.32; **p = 0.000**) (Figure 5) in male participants. In addition, there were no significant differences between participants with different BMI categories in terms of MAP, SAP, and DAP. Concerning cooling techniques, our results showed that cryostimulation induced slightly increased MAP (SMD = 0.27; **p = 0.000**), SAP (SMD = 0.40; **p = 0.000**) and DAP (SMD = 0.42; **p = 0.000**). However, there were no differences between the impacts of cooling techniques in terms of MAP, SAP, and DAP. Comparison between the effects of the different types of cryostimulation on arterial pressure showed that exposure to WBC induced a greater increase than the one observed with PBC in MAP (p = **0.035**), SAP (p = **0.001**) and DAP (p = **0.025**). Meta-regression analysis was in line with subgroup analysis, indicating no significant impact of age, sex, BMI, body fat percentage or cooling technique on MAP, SAP, and DAP. However, meta-regressions showed a significant
<figure><img src="image_3.png" /><figcaption>**Figure 2.** Effect of cold exposure on heart rate magnitude depending on sex, BMI, cooling technique, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p<0.001.</figcaption></figure>

## 2.2. Arterial pressure

Concerning the impact of cold exposure (cryostimulation and CWI) on arterial pressure, our findings revealed slightly increased MAP (SMD = 0.23; **p = 0.001**) (Figure 3), SAP (SMD = 0.31; **p = 0.000**) (Figure 4) and DAP (SMD = 0.32; **p = 0.000**) (Figure 5) in male participants. In addition, there were no significant differences between participants with different BMI categories in terms of MAP, SAP, and DAP. Concerning cooling techniques, our results showed that cryostimulation induced slightly increased MAP (SMD = 0.27; **p = 0.000**), SAP (SMD = 0.40; **p = 0.000**) and DAP (SMD = 0.42; **p = 0.000**). However, there were no differences between the impacts of cooling techniques in terms of MAP, SAP, and DAP. Comparison between the effects of the different types of cryostimulation on arterial pressure showed that exposure to WBC induced a greater increase than the one observed with PBC in MAP (p = **0.035**), SAP (p = **0.001**) and DAP (p = **0.025**). Meta-regression analysis was in line with subgroup analysis, indicating no significant impact of age, sex, BMI, body fat percentage or cooling technique on MAP, SAP, and DAP. However, meta-regressions showed a significant
moderating effect of cryostimulation type (PBC: coefficient = -0.60, 95% CI: -1.19 to -0.01; z = -1.98; p = 0.048) on SAP.

<figure><img src="image_3.png" /><figcaption>**Figure 3.** Effect of cold exposure on mean arterial pressure magnitude depending on sex, BMI, cooling technique, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.05.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>**Figure 4.** Effect of cold exposure on systolic arterial pressure magnitude depending on sex, BMI, cooling techniques, and cryostimulation type. BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.001</figcaption></figure>
moderating effect of cryostimulation type (PBC: coefficient = -0.60, 95% CI: -1.19 to -0.01; z = -1.98; p = 0.048) on SAP.

<figure><img src="image_4.png" /><figcaption>**Figure 3.** Effect of cold exposure on mean arterial pressure magnitude depending on sex, BMI, cooling technique, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.05.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>**Figure 4.** Effect of cold exposure on systolic arterial pressure magnitude depending on sex, BMI, cooling techniques, and cryostimulation type. BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.001</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 5.** Effect of cold exposure on diastolic arterial pressure magnitude depending on sex, BMI, cooling techniques, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.05.</figcaption></figure>

As depicted in Figure 6, time course analysis revealed progressively decreased HR, which remained for 30 min post-exposure (SMD = -0.17; **p** = **0.020**). However, the effect dissipated after this time lapse, as indicated by subsequently increased HR until a return to resting values. Additionally, time course analysis revealed a significant gradual decrease in MAP (SMD = 0.33; **p** = **0.000**), SAP (SMD = 0.29; **p** = **0.002**) and DAP (SMD = 0.45; **p** = **0.001**) (Figure 6) for up to 15 min following cold exposure. After 30 min post-exposure, effect size showed a slight increase in SAP (SMD = 0.44; **p** = **0.001**), and DAP (SMD = 0.34; **p** = **0.000**). However, blood pressure values remained in subclinical ranges (Table 4). Reference intervals for health-related blood pressure values (Master, 1950) are provided in Appendix 5 (see SM).
<figure><img src="image_6.png" /><figcaption>**Figure 5.** Effect of cold exposure on diastolic arterial pressure magnitude depending on sex, BMI, cooling techniques, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; CWI: Cold Water Immersion; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p< 0.05.</figcaption></figure>

As depicted in Figure 6, time course analysis revealed progressively decreased HR, which remained for 30 min post-exposure (SMD = -0.17; **p** = **0.020**). However, the effect dissipated after this time lapse, as indicated by subsequently increased HR until a return to resting values. Additionally, time course analysis revealed a significant gradual decrease in MAP (SMD = 0.33; **p** = **0.000**), SAP (SMD = 0.29; **p** = **0.002**) and DAP (SMD = 0.45; **p** = **0.001**) (Figure 6) for up to 15 min following cold exposure. After 30 min post-exposure, effect size showed a slight increase in SAP (SMD = 0.44; **p** = **0.001**), and DAP (SMD = 0.34; **p** = **0.000**). However, blood pressure values remained in subclinical ranges (Table 4). Reference intervals for health-related blood pressure values (Master, 1950) are provided in Appendix 5 (see SM).
<figure><img src="image_6.png" /><figcaption>**Figure 6.** Time course effect of cold exposure on cardiovascular system. SMD: Standardized mean difference; MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; \*:Significant effect at p< 0.05.</figcaption></figure>

<table><caption>**Table 4.** Arterial pressure magnitude over time after cold exposure</caption><thead><tr><th></th><th>Before</th><th>0 min</th><th>5-15 min</th><th>15-30 min</th><th>&gt; 30 min</th></tr></thead><tbody><tr><th>MAP (mmHg)</th><td>89.28 ± 7.94</td><td>94.95 ± 9.83</td><td>92.68 ± 9.33</td><td>87.81 ± 8.02</td><td>87.74 ± 8.32</td></tr><tr><th>SAP (mmHg)</th><td>122.07 ± 12.42</td><td>130.94 ± 13.49</td><td>125.29 ± 14.62</td><td>121.75 ± 10.10</td><td>121.06 ± 11.27</td></tr><tr><th>DAP (mmHg)</th><td>73.79 ± 7.21</td><td>78.24 ± 8.18</td><td>78.52 ± 7.41</td><td>74.32 ± 7.89</td><td>75.74 ± 7.70</td></tr></tbody></table>

MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure

### 3. Cardiac autonomic control

To our knowledge, there have been few if any scientific investigations exploring the effects of CWI on the autonomic nervous system without physical activity intervention. Therefore, we restricted our investigation to whole or partial body cryostimulation. Overall SMD showed that whole /partial body cryostimulation induced a significant change in cardiac autonomic control outcomes (Table 5). More precisely, pooled data showed a significant increase in R-R (SMD = 0.77; 95% CI: 0.55 to 0.98; z = 6.93; I² = 0.00; **p = 0.000**), RMSSD (SMD = 0.61; 95% CI: 0.43 to 0.79; z = 6.72; I² = 0.00; **p = 0.000**), and HF (SMD = 0.46; 95% CI: 0.25 to 0.68; z = 4.29; I² = 0.00; **p = 0.000**), as well as a significant decrease in LF (SMD = -0.41; 95% CI: -0.63 to -0.20; z = -3.82; I² = 4.83; **p = 0.000**) and LF/HF (SMD = -0.25; 95% CI: -0.42 to -0.09; z = -3.03; I² = 5.12; **p = 0.002**).
<figure><img src="image_7.png" /><figcaption>**Figure 6.** Time course effect of cold exposure on cardiovascular system. SMD: Standardized mean difference; MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure; \*:Significant effect at p< 0.05.</figcaption></figure>

<table><caption>**Table 4.** Arterial pressure magnitude over time after cold exposure</caption><thead><tr><th></th><th>Before</th><th>0 min</th><th>5-15 min</th><th>15-30 min</th><th>&gt; 30 min</th></tr></thead><tbody><tr><th>MAP (mmHg)</th><td>89.28 ± 7.94</td><td>94.95 ± 9.83</td><td>92.68 ± 9.33</td><td>87.81 ± 8.02</td><td>87.74 ± 8.32</td></tr><tr><th>SAP (mmHg)</th><td>122.07 ± 12.42</td><td>130.94 ± 13.49</td><td>125.29 ± 14.62</td><td>121.75 ± 10.10</td><td>121.06 ± 11.27</td></tr><tr><th>DAP (mmHg)</th><td>73.79 ± 7.21</td><td>78.24 ± 8.18</td><td>78.52 ± 7.41</td><td>74.32 ± 7.89</td><td>75.74 ± 7.70</td></tr></tbody></table>

MAP: Mean Arterial pressure; SAP: Systolic arterial pressure; DAP: Diastolic arterial pressure

### 3. Cardiac autonomic control

To our knowledge, there have been few if any scientific investigations exploring the effects of CWI on the autonomic nervous system without physical activity intervention. Therefore, we restricted our investigation to whole or partial body cryostimulation. Overall SMD showed that whole /partial body cryostimulation induced a significant change in cardiac autonomic control outcomes (Table 5). More precisely, pooled data showed a significant increase in R-R (SMD = 0.77; 95% CI: 0.55 to 0.98; z = 6.93; I² = 0.00; **p = 0.000**), RMSSD (SMD = 0.61; 95% CI: 0.43 to 0.79; z = 6.72; I² = 0.00; **p = 0.000**), and HF (SMD = 0.46; 95% CI: 0.25 to 0.68; z = 4.29; I² = 0.00; **p = 0.000**), as well as a significant decrease in LF (SMD = -0.41; 95% CI: -0.63 to -0.20; z = -3.82; I² = 4.83; **p = 0.000**) and LF/HF (SMD = -0.25; 95% CI: -0.42 to -0.09; z = -3.03; I² = 5.12; **p = 0.002**).
<table><caption>Table 5. Overall effect of Whole/Partial Body cryostimulation on cardiac autonomic control.</caption><thead><tr><th></th><th>participants<br>(s)</th><th>Experimental<br>groups (n)</th><th>Level of<br>evidence</th><th>SMD</th><th>CI 95 %</th><th>p</th></tr></thead><tbody><tr><td>R-R</td><td>110</td><td>10</td><td>Strong</td><td>0.77</td><td>0.55; 0.98</td><td><strong>0.000</strong></td></tr><tr><td>RMSSD</td><td>146</td><td>13</td><td>Strong</td><td>0.61</td><td>0.43; 0.79</td><td><strong>0.000</strong></td></tr><tr><td>HF</td><td>221</td><td>16</td><td>Strong</td><td>0.46</td><td>0.25; 0.68</td><td><strong>0.000</strong></td></tr><tr><td>LF</td><td>221</td><td>16</td><td>Strong</td><td>-0.41</td><td>-0.63; -0.20</td><td><strong>0.000</strong></td></tr><tr><td>LF/HF</td><td>221</td><td>16</td><td>Strong</td><td>-0.25</td><td>-0.42; -0.09</td><td><strong>0.002</strong></td></tr></tbody></table>

RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; HR: Heart rate; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low-high frequency power; SMD: Standardized mean difference; CI: confidence interval.

Time course analysis revealed significantly increased RMSSD (SMD = 0.53; **p = 0.000**), RR (SMD = 0.76; **p = 0.000**) and HF (SMD = 0.58; **p = 0.000**) up to 15 min post-exposure (Figure 7). Thirty minutes after exposure, we observed slightly increased LF and decreased HF and LF/HF ratio.

<figure><img src="image_7.png" /><figcaption>**Figure 7.** Time course effect of cold exposure on cardiac autonomic control. SMD: Standardized mean difference; RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; HR: Heart rate; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low-high frequency power; *:Significant effect at p<0.05.</figcaption></figure>
<table><caption>Table 5. Overall effect of Whole/Partial Body cryostimulation on cardiac autonomic control.</caption><thead><tr><th></th><th>participants<br>(s)</th><th>Experimental<br>groups (n)</th><th>Level of<br>evidence</th><th>SMD</th><th>CI 95 %</th><th>p</th></tr></thead><tbody><tr><td>R-R</td><td>110</td><td>10</td><td>Strong</td><td>0.77</td><td>0.55; 0.98</td><td><strong>0.000</strong></td></tr><tr><td>RMSSD</td><td>146</td><td>13</td><td>Strong</td><td>0.61</td><td>0.43; 0.79</td><td><strong>0.000</strong></td></tr><tr><td>HF</td><td>221</td><td>16</td><td>Strong</td><td>0.46</td><td>0.25; 0.68</td><td><strong>0.000</strong></td></tr><tr><td>LF</td><td>221</td><td>16</td><td>Strong</td><td>-0.41</td><td>-0.63; -0.20</td><td><strong>0.000</strong></td></tr><tr><td>LF/HF</td><td>221</td><td>16</td><td>Strong</td><td>-0.25</td><td>-0.42; -0.09</td><td><strong>0.002</strong></td></tr></tbody></table>

RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; HR: Heart rate; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low-high frequency power; SMD: Standardized mean difference; CI: confidence interval.

Time course analysis revealed significantly increased RMSSD (SMD = 0.53; **p = 0.000**), RR (SMD = 0.76; **p = 0.000**) and HF (SMD = 0.58; **p = 0.000**) up to 15 min post-exposure (Figure 7). Thirty minutes after exposure, we observed slightly increased LF and decreased HF and LF/HF ratio.

<figure><img src="image_8.png" /><figcaption>**Figure 7.** Time course effect of cold exposure on cardiac autonomic control. SMD: Standardized mean difference; RMSSD: root-mean square difference of successive R-R intervals; R-R: R-R heart rate intervals; HR: Heart rate; High frequency (HF), LF: Low frequency; LF/HF: Ratio of low-high frequency power; *:Significant effect at p<0.05.</figcaption></figure>
### 3.1. R-R intervals

Cryostimulation induced a significant increase in R-R intervals in all BMI categories (normal-weight (SMD = 0.63; **p** = 0.000) and overweight (SMD = 1.18; **p** = 0.000) participants following cryostimulation (WBC (SMD = 0.74; **p** = 0.000) and PBC (SMD = 0.83; **p** = 0.000)) (Figure 8). Regarding BMI categories, there was a significant difference between normal-weight and overweight participants (**p** = 0.015). The meta-regression analysis was aligned with the subgroup findings, indicating that higher BMI (coefficient = 0.56; 95% CI: 0.06 to 1.06; z = 2.18; **p** = 0.029) and elevated body fat percentage (coefficient = 0.82, 95% CI: 0.11 to 1.54; z = 2.26; **p** = 0.024) are linked to a greater increase in R-R intervals following cryostimulation exposure. Of note, meta-regression analysis did not show a significant effect of age in moderating RR interval outcomes. Moreover, the subgroup analysis did not indicate a significant impact of type of cryostimulation on R-R intervals. Meta-regression did not contradict this finding.

<figure><img src="image_8.png" /></figure>

### 3.2. RMSSD

Cryostimulation induced a significant increase in RMSSD across various groups : in men (SMD = 0.57; **p** = 0.000) and women (SMD = 0.90; **p** = 0.023), normal-weight (SMD = 0.63; **p** = 0.000) and overweight (SMD = 0.57; **p** = 0.002) participants, following WBC (SMD = 0.62; **p** = 0.000) and PBC (SMD = 0.61; **p** = 0.000) without any difference between moderators (Figure 9). Meta-regression analysis confirmed these results and showed that the increase in RMSSD was not significantly modulated by age, sex, BMI, body fat percentage, or cryostimulation type.
### 3.1. R-R intervals

Cryostimulation induced a significant increase in R-R intervals in all BMI categories (normal-weight (SMD = 0.63; **p** = 0.000) and overweight (SMD = 1.18; **p** = 0.000) participants following cryostimulation (WBC (SMD = 0.74; **p** = 0.000) and PBC (SMD = 0.83; **p** = 0.000)) (Figure 8). Regarding BMI categories, there was a significant difference between normal-weight and overweight participants (**p** = 0.015). The meta-regression analysis was aligned with the subgroup findings, indicating that higher BMI (coefficient = 0.56; 95% CI: 0.06 to 1.06; z = 2.18; **p** = 0.029) and elevated body fat percentage (coefficient = 0.82, 95% CI: 0.11 to 1.54; z = 2.26; **p** = 0.024) are linked to a greater increase in R-R intervals following cryostimulation exposure. Of note, meta-regression analysis did not show a significant effect of age in moderating RR interval outcomes. Moreover, the subgroup analysis did not indicate a significant impact of type of cryostimulation on R-R intervals. Meta-regression did not contradict this finding.

<figure><img src="image_9.png" /></figure>

### 3.2. RMSSD

Cryostimulation induced a significant increase in RMSSD across various groups : in men (SMD = 0.57; **p** = 0.000) and women (SMD = 0.90; **p** = 0.023), normal-weight (SMD = 0.63; **p** = 0.000) and overweight (SMD = 0.57; **p** = 0.002) participants, following WBC (SMD = 0.62; **p** = 0.000) and PBC (SMD = 0.61; **p** = 0.000) without any difference between moderators (Figure 9). Meta-regression analysis confirmed these results and showed that the increase in RMSSD was not significantly modulated by age, sex, BMI, body fat percentage, or cryostimulation type.
<figure><img src="image_9.png" /><figcaption>**Figure 9.** Effect of cold exposure on RMSSD magnitude depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: subjects participants.</figcaption></figure>

### 3.3. HF

Cryostimulation induced a significant increase in HF in males (SMD = 0.42; **p = 0.000**) and normal-weight participants (SMD = 0.63; **p = 0.000**) (Figure 10). We found a significant difference between BMI categories (**p = 0.021**). Moreover, our results showed a significant increase following both WBC (SMD = 0.28; **p = 0.008**) and PBC (SMD = 0.78; **p = 0.000**). Significant difference between the two cryostimulation types (**p = 0.008**) was also noted. More precisely, a greater increase in HF was found following PBC compared to WBC. Meta-regression analysis confirmed that BMI (Overweight: coefficient = -0.41, 95% CI: -0.78 to -0.05; z = -2.21; **p = 0.027**) and cryostimulation type (PBC: coefficient = 0.48, 95% CI: 0.09 to 0.87; z = 2.42; **p = 0.015**) significantly influenced the magnitude of HF increase. Conversely, age, sex, and body fat percentage did not have a significant effect on HF outcomes after cryostimulation exposure.
<figure><img src="image_10.png" /><figcaption>**Figure 9.** Effect of cold exposure on RMSSD magnitude depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: subjects participants.</figcaption></figure>

### 3.3. HF

Cryostimulation induced a significant increase in HF in males (SMD = 0.42; **p = 0.000**) and normal-weight participants (SMD = 0.63; **p = 0.000**) (Figure 10). We found a significant difference between BMI categories (**p = 0.021**). Moreover, our results showed a significant increase following both WBC (SMD = 0.28; **p = 0.008**) and PBC (SMD = 0.78; **p = 0.000**). Significant difference between the two cryostimulation types (**p = 0.008**) was also noted. More precisely, a greater increase in HF was found following PBC compared to WBC. Meta-regression analysis confirmed that BMI (Overweight: coefficient = -0.41, 95% CI: -0.78 to -0.05; z = -2.21; **p = 0.027**) and cryostimulation type (PBC: coefficient = 0.48, 95% CI: 0.09 to 0.87; z = 2.42; **p = 0.015**) significantly influenced the magnitude of HF increase. Conversely, age, sex, and body fat percentage did not have a significant effect on HF outcomes after cryostimulation exposure.
<figure><img src="image_10.png" /></figure>

**Figure 10.** Effect of cold exposure on HF magnitude depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole Body Cryostimulation; PBC: Partial Body Cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p < 0.05.

### 3.4. LF

In accordance with the results in HF outcome, a significant decrease in LF was reported following cryostimulation only in men (SMD = -0.36; **p** = **0.001**) and in normal-weight participants (SMD = -0.59; **p** = **0.000**) (Figure 11). A more pronounced decrease in HF was observed in normal weight compared to overweight participants (**p** = **0.012**). On the contrary, no significant differences were found regarding sex. In addition, our results showed a significant decrease in LF following both WBC (SMD = -0.23; **p** = **0.020**) and PBC (SMD = -0.74; **p** = **0.000**). PBC exposure led to greater reduction in LF compared to the data collected after WBC exposure (**p** = **0.014**). Meta-regression analysis supported these results, showing that BMI (Overweight: coefficient = 0.41, 95% CI: 0.04 to 0.78; z = 2.18; **p** = **0.029**) and type of cryostimulation therapy (PBC: coefficient = -0.46, 95% CI: -0.86 to -0.06; z = -2.27 **p** = **0.023**) influenced the LF decrease. However, moderators such as age, sex, and body fat percentage did not show a significant effect on post-cryostimulation HF changes.
<figure><img src="image_11.png" /></figure>

**Figure 10.** Effect of cold exposure on HF magnitude depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole Body Cryostimulation; PBC: Partial Body Cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at p < 0.05.

### 3.4. LF

In accordance with the results in HF outcome, a significant decrease in LF was reported following cryostimulation only in men (SMD = -0.36; **p** = **0.001**) and in normal-weight participants (SMD = -0.59; **p** = **0.000**) (Figure 11). A more pronounced decrease in HF was observed in normal weight compared to overweight participants (**p** = **0.012**). On the contrary, no significant differences were found regarding sex. In addition, our results showed a significant decrease in LF following both WBC (SMD = -0.23; **p** = **0.020**) and PBC (SMD = -0.74; **p** = **0.000**). PBC exposure led to greater reduction in LF compared to the data collected after WBC exposure (**p** = **0.014**). Meta-regression analysis supported these results, showing that BMI (Overweight: coefficient = 0.41, 95% CI: 0.04 to 0.78; z = 2.18; **p** = **0.029**) and type of cryostimulation therapy (PBC: coefficient = -0.46, 95% CI: -0.86 to -0.06; z = -2.27 **p** = **0.023**) influenced the LF decrease. However, moderators such as age, sex, and body fat percentage did not show a significant effect on post-cryostimulation HF changes.
<figure><img src="image_11.png" /></figure>

**Figure 11.** Effect of cold exposure on LF magnitude depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at *p* < 0.05.

### 3.5. LF/HF ratio

Our results demonstrated that cryostimulation exposure elicits a significant decrease in men (SMD = -0.23; **p= 0.014**), and in overweight participants (SMD = -0.24; **p = 0.015**) following WBC (SMD = -0.25; **p= 0.010**), as shown in Figure 12. However, we did not observe any significant difference according to sex, BMI, and type of cryostimulation. Consistently, meta-regression analysis showed no significant effect on age, sex, body fat percent, BMI, and type of cryostimulation.

<figure><img src="image_12.png" /></figure>

**Figure 12.** Effect of cold exposure on LF/HF depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants
<figure><img src="image_12.png" /></figure>

**Figure 11.** Effect of cold exposure on LF magnitude depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants; *: Significant difference between moderators at *p* < 0.05.

### 3.5. LF/HF ratio

Our results demonstrated that cryostimulation exposure elicits a significant decrease in men (SMD = -0.23; **p= 0.014**), and in overweight participants (SMD = -0.24; **p = 0.015**) following WBC (SMD = -0.25; **p= 0.010**), as shown in Figure 12. However, we did not observe any significant difference according to sex, BMI, and type of cryostimulation. Consistently, meta-regression analysis showed no significant effect on age, sex, body fat percent, BMI, and type of cryostimulation.

<figure><img src="image_13.png" /></figure>

**Figure 12.** Effect of cold exposure on LF/HF depending on sex, BMI, and cryostimulation type. SMD: Standardized mean difference; BMI: Body Mass Index; Cryo: cryostimulation; WBC: Whole body cryostimulation; PBC: Partial Body cryostimulation; N: Number of articles; n: Number of experimental groups; s: Number of participants
Discussion

The aim of the present meta-analysis is to provide a comprehensive overview of the available
scientific literature examining the effects of cold exposure (cryostimulation and CWI) on
cardiovascular and cardiac autonomic control responses in healthy participants. Our results
suggested enhanced parasympathetic activity and reduced sympathetic nervous activity
following cold exposure. These findings are supported by changes in HRV indices, through
increased RMSSD, R-R interval, and HF, as well as significantly decreased LF and LF/HF ratio.
Furthermore, our results examining cardiovascular responses to cold exposure indicated
significantly reduced heart rate, accompanied by a slightly increased blood pressure. Our
findings are consistent with the results reported by previous studies (Guolo and Varin, 2017;
Hausswirth et al., 2013; Westerlund et al., 2006; Zalewski et al., 2014a). In response to changes
in ambient temperature, the cutaneous blood vessels can dynamically dilate or constrict. These
mechanisms play a crucial role in the regulation of body temperature by controlling heat loss.
When the body is exposed to cold temperatures, the sympathetic α-adrenergic receptors are
activated, resulting in the constriction of peripheral blood vessels (Zalewski et al., 2014b).
Previous studies have consistently demonstrated that peripheral vasoconstriction inhibits heat
loss, leading to a marked reduction in skin capillary perfusion. As a result, blood flow is
redirected toward the center, raising arterial pressure (Hausswirth et al., 2013). Our findings are
in line with the results of Lubkowska and Szyguła (2010) highlighting that WBC is associated
with an elevation in blood pressure along with a compensatory decrease in heart rate. This
observation can be explained by the stimulation of baroreceptors located in the carotid sinus
and the aortic arch. Specifically, when blood pressure increases, these sensory receptors activate
the autonomic bulb centers (Reutersberg et al., 2022). In response to this stimulation, a
subsequent parasympathetic reactivation leads to a decrease in heart rate (Pump et al., 2001),
as demonstrated in our study's overall cold exposure effect. Additionally, our outcomes
regarding the overall effect of cryostimulation on the cardiac autonomic control system are in
agreement with the findings reported in previous works (Hausswirth et al., 2013; Westerlund et
al., 2006; Zalewski et al., 2014b). It has been shown that cryostimulation effectively increase
R-R intervals, RMSSD, and HF bands, which are recognized indicators of enhanced
parasympathetic tone activation (Hausswirth et al., 2013; Westerlund et al., 2006; Zalewski et
al., 2014a). By initiating parasympathetic activation, baroreceptor stimulation helps to maintain
homeostasis by counterbalancing the sympathetic response induced by cold exposure. These
observed physiological responses may underlie cold exposure benefits (cryostimulation and
Discussion

The aim of the present meta-analysis is to provide a comprehensive overview of the available
scientific literature examining the effects of cold exposure (cryostimulation and CWI) on
cardiovascular and cardiac autonomic control responses in healthy participants. Our results
suggested enhanced parasympathetic activity and reduced sympathetic nervous activity
following cold exposure. These findings are supported by changes in HRV indices, through
increased RMSSD, R-R interval, and HF, as well as significantly decreased LF and LF/HF ratio.
Furthermore, our results examining cardiovascular responses to cold exposure indicated
significantly reduced heart rate, accompanied by a slightly increased blood pressure. Our
findings are consistent with the results reported by previous studies (Guolo and Varin, 2017;
Hausswirth et al., 2013; Westerlund et al., 2006; Zalewski et al., 2014a). In response to changes
in ambient temperature, the cutaneous blood vessels can dynamically dilate or constrict. These
mechanisms play a crucial role in the regulation of body temperature by controlling heat loss.
When the body is exposed to cold temperatures, the sympathetic α-adrenergic receptors are
activated, resulting in the constriction of peripheral blood vessels (Zalewski et al., 2014b).
Previous studies have consistently demonstrated that peripheral vasoconstriction inhibits heat
loss, leading to a marked reduction in skin capillary perfusion. As a result, blood flow is
redirected toward the center, raising arterial pressure (Hausswirth et al., 2013). Our findings are
in line with the results of Lubkowska and Szyguła (2010) highlighting that WBC is associated
with an elevation in blood pressure along with a compensatory decrease in heart rate. This
observation can be explained by the stimulation of baroreceptors located in the carotid sinus
and the aortic arch. Specifically, when blood pressure increases, these sensory receptors activate
the autonomic bulb centers (Reutersberg et al., 2022). In response to this stimulation, a
subsequent parasympathetic reactivation leads to a decrease in heart rate (Pump et al., 2001),
as demonstrated in our study's overall cold exposure effect. Additionally, our outcomes
regarding the overall effect of cryostimulation on the cardiac autonomic control system are in
agreement with the findings reported in previous works (Hausswirth et al., 2013; Westerlund et
al., 2006; Zalewski et al., 2014b). It has been shown that cryostimulation effectively increase
R-R intervals, RMSSD, and HF bands, which are recognized indicators of enhanced
parasympathetic tone activation (Hausswirth et al., 2013; Westerlund et al., 2006; Zalewski et
al., 2014a). By initiating parasympathetic activation, baroreceptor stimulation helps to maintain
homeostasis by counterbalancing the sympathetic response induced by cold exposure. These
observed physiological responses may underlie cold exposure benefits (cryostimulation and
CWI) such as enhanced recovery after exercise, better sympatho-vagal balance, reduced perceived pain, and improved sleep quality (Douzi et al., 2019b, 2019a; Moore et al., 2023). The above findings, particularly increased cardiac parasympathetic activity, have been consistently linked with better overall health and well-being (Louis et al., 2015; Udo et al., 2013). Our results show that parasympathetic activation persists up to 15 min after exposure. To completely comprehend time course analysis of HRV after cold exposure, further research is required. Expanding the number of studies would facilitate exploration of the immediate and prolonged effects of various factors on HRV.

The subgroup and meta-regression analysis results indicate a significant change in cardiovascular and cardiac autonomic control outcomes following cold exposure. The studies included focused primarily on male participants, leading to a significant effect in this subgroup. The small number of female participants in these studies may reduce the statistical power to detect significant effect in this subgroup, which is why it is important to interpret these results cautiously. Without a more extensive body of literature and larger sample sizes, it is challenging to draw a definitive conclusion about the sex-specific effects of cold exposure on cardiovascular and cardiac autonomic control outcomes.

Our findings also showed that while BMI and body fat percentage do not significantly affect cardiovascular variables, they significantly affect heart rate variability, specifically the RR interval. Greater increase in RR interval outcomes was observed in overweight compared to normal weight individuals. This finding may suggest a more pronounced compensatory parasympathetic response, possibly due to different baseline autonomic balance or a different adaptive mechanism to cold stress. In fact, excess body fat, particularly visceral fat, may be associated with pro-inflammatory cytokine secretion, leading to an increased sympathetic tone (Hillebrand et al., 2014). Conversely, normal-weight individuals manifested a more significant effect on HF and LF outcomes post-cryostimulation, with no notable impact of body fat percentage. These contradictory findings highlight that the exact mechanisms through which cryostimulation affects autonomic function, especially in relation to body composition, remain an area of ongoing research. Additionally, we wish to emphasize to highlight that the studies included in our meta-analysis did not specifically focus on examining the interaction between BMI categories. Consequently, the sample sizes for each BMI group may have been insufficient to detect significant differences. A larger sample size and more specific study design could help to provide a clearer understanding of any potential associations between BMI categories and cold exposure effects.
CWI) such as enhanced recovery after exercise, better sympatho-vagal balance, reduced perceived pain, and improved sleep quality (Douzi et al., 2019b, 2019a; Moore et al., 2023). The above findings, particularly increased cardiac parasympathetic activity, have been consistently linked with better overall health and well-being (Louis et al., 2015; Udo et al., 2013). Our results show that parasympathetic activation persists up to 15 min after exposure. To completely comprehend time course analysis of HRV after cold exposure, further research is required. Expanding the number of studies would facilitate exploration of the immediate and prolonged effects of various factors on HRV.

The subgroup and meta-regression analysis results indicate a significant change in cardiovascular and cardiac autonomic control outcomes following cold exposure. The studies included focused primarily on male participants, leading to a significant effect in this subgroup. The small number of female participants in these studies may reduce the statistical power to detect significant effect in this subgroup, which is why it is important to interpret these results cautiously. Without a more extensive body of literature and larger sample sizes, it is challenging to draw a definitive conclusion about the sex-specific effects of cold exposure on cardiovascular and cardiac autonomic control outcomes.

Our findings also showed that while BMI and body fat percentage do not significantly affect cardiovascular variables, they significantly affect heart rate variability, specifically the RR interval. Greater increase in RR interval outcomes was observed in overweight compared to normal weight individuals. This finding may suggest a more pronounced compensatory parasympathetic response, possibly due to different baseline autonomic balance or a different adaptive mechanism to cold stress. In fact, excess body fat, particularly visceral fat, may be associated with pro-inflammatory cytokine secretion, leading to an increased sympathetic tone (Hillebrand et al., 2014). Conversely, normal-weight individuals manifested a more significant effect on HF and LF outcomes post-cryostimulation, with no notable impact of body fat percentage. These contradictory findings highlight that the exact mechanisms through which cryostimulation affects autonomic function, especially in relation to body composition, remain an area of ongoing research. Additionally, we wish to emphasize to highlight that the studies included in our meta-analysis did not specifically focus on examining the interaction between BMI categories. Consequently, the sample sizes for each BMI group may have been insufficient to detect significant differences. A larger sample size and more specific study design could help to provide a clearer understanding of any potential associations between BMI categories and cold exposure effects.
In our meta-analysis, we refrained from conducting a subgroup analysis to investigate the impact of physical level on cold exposure outcomes. It is worth noting that only one of the studies included participants who were untrained. In the other selected works, the volunteers were physically active, or else the relevant information was not available. In addition, our included studies mainly featured young participants, typically under the age of 35. Their homogeneity suggests that age did not emerge as a significant moderator in our analysis. Therefore, limited diversity in physical activity levels and age range restricted exploration of their impact on cold-induced responses. Further research involving more varied participant characteristics is necessary.

Our findings also showed that cryostimulation is more effective than CWI in modifying cardiovascular variables such as BP and HR. Cryostimulation is exposure to extremely low temperatures, often below -100°C, while CWI concerns time of exposure to temperatures below 15°C (Machado et al., 2016). Exposure to very low temperatures may cause a more pronounced physiological reaction, such as vasoconstriction. In this context, Costello et al. (2013) noted that while cryostimulation and CWI were both effective in reducing skin temperature, cryostimulation induced a greater decrease than CWI. It is important to note that scientific studies comparing the impact of CWI and cryostimulation on cardiac autonomic control and cardiovascular responses are lacking.

Additionally, our meta-analysis revealed that compared to PBC, WBC induces significant changes in arterial blood pressure (MAP, SAP, DAP). This finding is consistent with the study by Hausswirth et al. (2013) which confirms that SBP and DBP significantly increase after WBC, but not after PBC. The observed decrease in blood pressure after PBC may be attributed to a reduced level of sympathetic stimulation possibly due to a less pronounced decrease in skin temperature (Hausswirth et al., 2013). Generally, the observed increase in BP is probably associated with a large decrease in HR. In fact, the stimulation of cold trigemino-cardiac reflex receptors located in the face may accentuate the parasympathetic response after WBC by increasing vagal output to the heart (Hausswirth et al., 2013; Louis et al., 2015). Nevertheless, our results showed that compared to WBC, PBC is more effective in reducing HR, increasing HF, and decreasing LF. Additionally, our meta-analysis demonstrated that both WBC and PBC increased RMSSD and decreased LF/HF ratio. Louis et al. (2015) corroborate these findings, as they observed that both cryostimulation techniques effectively stimulated cardiac autonomic control with predominantly parasympathetic drive (Louis et al., 2015). The seemingly contradictory results could be attributed to the limited number of studies using
In our meta-analysis, we refrained from conducting a subgroup analysis to investigate the impact of physical level on cold exposure outcomes. It is worth noting that only one of the studies included participants who were untrained. In the other selected works, the volunteers were physically active, or else the relevant information was not available. In addition, our included studies mainly featured young participants, typically under the age of 35. Their homogeneity suggests that age did not emerge as a significant moderator in our analysis. Therefore, limited diversity in physical activity levels and age range restricted exploration of their impact on cold-induced responses. Further research involving more varied participant characteristics is necessary.

Our findings also showed that cryostimulation is more effective than CWI in modifying cardiovascular variables such as BP and HR. Cryostimulation is exposure to extremely low temperatures, often below -100°C, while CWI concerns time of exposure to temperatures below 15°C (Machado et al., 2016). Exposure to very low temperatures may cause a more pronounced physiological reaction, such as vasoconstriction. In this context, Costello et al. (2013) noted that while cryostimulation and CWI were both effective in reducing skin temperature, cryostimulation induced a greater decrease than CWI. It is important to note that scientific studies comparing the impact of CWI and cryostimulation on cardiac autonomic control and cardiovascular responses are lacking.

Additionally, our meta-analysis revealed that compared to PBC, WBC induces significant changes in arterial blood pressure (MAP, SAP, DAP). This finding is consistent with the study by Hausswirth et al. (2013) which confirms that SBP and DBP significantly increase after WBC, but not after PBC. The observed decrease in blood pressure after PBC may be attributed to a reduced level of sympathetic stimulation possibly due to a less pronounced decrease in skin temperature (Hausswirth et al., 2013). Generally, the observed increase in BP is probably associated with a large decrease in HR. In fact, the stimulation of cold trigemino-cardiac reflex receptors located in the face may accentuate the parasympathetic response after WBC by increasing vagal output to the heart (Hausswirth et al., 2013; Louis et al., 2015). Nevertheless, our results showed that compared to WBC, PBC is more effective in reducing HR, increasing HF, and decreasing LF. Additionally, our meta-analysis demonstrated that both WBC and PBC increased RMSSD and decreased LF/HF ratio. Louis et al. (2015) corroborate these findings, as they observed that both cryostimulation techniques effectively stimulated cardiac autonomic control with predominantly parasympathetic drive (Louis et al., 2015). The seemingly contradictory results could be attributed to the limited number of studies using
PBC. It is important to recognize that the inclusion of more research articles utilizing PBC could permit clearer and more consistent understanding of the outcomes.

The thermal outcomes reported in the studies included in our systematic review revealed significant changes in skin, tympanic, core, and rectal temperature in response to WBC, PBC, and CWI exposure. More specifically, WBC and PBC induced a significant and immediate decrease in skin temperature across all body regions, with greater reduction in the lower limbs. The decrease was more pronounced with exposure at lower temperatures and longer exposure times. In some studies, this decrease persisted up to 20 minutes post-exposure (Dębiec-Bąk et al., 2013; Louis et al., 2015).

Skin temperature is a crucial indicator of peripheral vasoconstriction, a key mechanism to reduce heat loss and maintain core body temperature under cold stress (Westerlund et al., 2003). In terms of tympanic temperature, a decrease was observed solely in WBC (Hausswirth et al., 2013), or was found to be more pronounced in WBC compared to PBC (Louis et al., 2020). This discrepancy could be attributed to head exposure during WBC, which does not occur in PBC. Additionally, changes in core body and rectal temperature were observed across various studies involving different durations and CWI and WBC. temperatures. Core body temperature was shown to decrease after 35 min (Cuttell et al., 2017) and between 50-60 min (Zalewski et al., 2014a) following WBC. Concerning CWI, rectal temperature (T°re) was reported to decrease at 60 min (Muller et al., 2012) during CWI, and from 45 to 70 min after CWI (Eimonte et al., 2021). These changes, particularly the afterdrop in core body and rectal temperature, may be attributed to the conduction of cold blood from the periphery to the core of the body.

The methodological quality of the studies included in this meta-analysis, evaluated using the PEDro scale, exhibited scores ranging from 4 to 8. It is noteworthy that a majority were classified as high-quality, which supports the reliability of their findings. However, medium-quality scores in certain studies are indicative of specific methodological limitations that should be considered when interpreting the results. This variability in scores also highlights the diverse research designs and protocols, underscoring a need for careful consideration when generalizing the findings. A common methodological limitation was related to blinding. Nevertheless, it is crucial to note the challenges associated with implementing blinding in interventions involving extreme stimuli like cold exposure. Moreover, issues pertaining to random allocation and participant assignment in some of the included studies could potentially have influenced the study outcomes. In summary, while the results of our systematic review are supported by studies with generally high methodological quality, it is important to note
PBC. It is important to recognize that the inclusion of more research articles utilizing PBC could permit clearer and more consistent understanding of the outcomes.

The thermal outcomes reported in the studies included in our systematic review revealed significant changes in skin, tympanic, core, and rectal temperature in response to WBC, PBC, and CWI exposure. More specifically, WBC and PBC induced a significant and immediate decrease in skin temperature across all body regions, with greater reduction in the lower limbs. The decrease was more pronounced with exposure at lower temperatures and longer exposure times. In some studies, this decrease persisted up to 20 minutes post-exposure (Dębiec-Bąk et al., 2013; Louis et al., 2015).

Skin temperature is a crucial indicator of peripheral vasoconstriction, a key mechanism to reduce heat loss and maintain core body temperature under cold stress (Westerlund et al., 2003). In terms of tympanic temperature, a decrease was observed solely in WBC (Hausswirth et al., 2013), or was found to be more pronounced in WBC compared to PBC (Louis et al., 2020). This discrepancy could be attributed to head exposure during WBC, which does not occur in PBC. Additionally, changes in core body and rectal temperature were observed across various studies involving different durations and CWI and WBC. temperatures. Core body temperature was shown to decrease after 35 min (Cuttell et al., 2017) and between 50-60 min (Zalewski et al., 2014a) following WBC. Concerning CWI, rectal temperature (T°re) was reported to decrease at 60 min (Muller et al., 2012) during CWI, and from 45 to 70 min after CWI (Eimonte et al., 2021). These changes, particularly the afterdrop in core body and rectal temperature, may be attributed to the conduction of cold blood from the periphery to the core of the body.

The methodological quality of the studies included in this meta-analysis, evaluated using the PEDro scale, exhibited scores ranging from 4 to 8. It is noteworthy that a majority were classified as high-quality, which supports the reliability of their findings. However, medium-quality scores in certain studies are indicative of specific methodological limitations that should be considered when interpreting the results. This variability in scores also highlights the diverse research designs and protocols, underscoring a need for careful consideration when generalizing the findings. A common methodological limitation was related to blinding. Nevertheless, it is crucial to note the challenges associated with implementing blinding in interventions involving extreme stimuli like cold exposure. Moreover, issues pertaining to random allocation and participant assignment in some of the included studies could potentially have influenced the study outcomes. In summary, while the results of our systematic review are supported by studies with generally high methodological quality, it is important to note
the limitations, particularly concerning blinding and allocation processes. Addressing these issues in future research may ensure more accurate and reliable interpretations of intervention outcomes.

## Conclusion

In conclusion, the present meta-analysis showed that exposure to cryostimulation and CWI induces changes in cardiovascular and cardiac autonomic control activities. These findings revealed enhanced parasympathetic nervous activity leading to reduced HR following cold exposure (CWI and cryostimulation). Overall, the cold-induced cardiac parasympathetic dominance may explain the potential benefits of these cooling techniques, which could consequently be a valuable intervention in the contexts of recovery after physical exercise, therapeutic exigencies, and general wellness practices. Time course analysis is characterized by parasympathetic activation during the initial 15 minutes after exposure, followed by a gradual return to the homeostatic level over the course of 30 minutes. More research is required to completely comprehend the time course analysis of HRV after cold exposure. Our meta-analysis also revealed a noteworthy gap in the current literature regarding the impact of sex, age, BMI, and physical level on cardiovascular and cardiac autonomic control after cold exposure. Filling this gap might provide valuable insights helping to optimize cold exposure strategies and their applications in various contexts.

## Strengths, limitations, and perspectives

Our meta-analysis represents the first comprehensive examination of how cold exposure (CWI, WBC, and PBC) affects cardiovascular and cardiac autonomic control responses in healthy individuals. It offers a global overview of existing scientific literature in this field. Importantly, the research was conducted without any language or year restrictions, ensuring a wide-ranging exploration of the available literature. Additionally, the study followed updated PRISMA recommendations. Furthermore, it consisted largely in a time course analysis of HRV, HR and BP revealing the dynamics of autonomic and cardiovascular responses after cold exposure. This temporal perspective enhances comprehension of post-exposure physiological changes. Nevertheless, it is important to acknowledge that additional research is needed to ensure deeper understanding of the immediate and prolonged responses. Another strength is that our study explores the impact of cold exposure according to moderators on the concerned outcomes. While this perspective may help to understand the different reactions of
the limitations, particularly concerning blinding and allocation processes. Addressing these issues in future research may ensure more accurate and reliable interpretations of intervention outcomes.

## Conclusion

In conclusion, the present meta-analysis showed that exposure to cryostimulation and CWI induces changes in cardiovascular and cardiac autonomic control activities. These findings revealed enhanced parasympathetic nervous activity leading to reduced HR following cold exposure (CWI and cryostimulation). Overall, the cold-induced cardiac parasympathetic dominance may explain the potential benefits of these cooling techniques, which could consequently be a valuable intervention in the contexts of recovery after physical exercise, therapeutic exigencies, and general wellness practices. Time course analysis is characterized by parasympathetic activation during the initial 15 minutes after exposure, followed by a gradual return to the homeostatic level over the course of 30 minutes. More research is required to completely comprehend the time course analysis of HRV after cold exposure. Our meta-analysis also revealed a noteworthy gap in the current literature regarding the impact of sex, age, BMI, and physical level on cardiovascular and cardiac autonomic control after cold exposure. Filling this gap might provide valuable insights helping to optimize cold exposure strategies and their applications in various contexts.

## Strengths, limitations, and perspectives

Our meta-analysis represents the first comprehensive examination of how cold exposure (CWI, WBC, and PBC) affects cardiovascular and cardiac autonomic control responses in healthy individuals. It offers a global overview of existing scientific literature in this field. Importantly, the research was conducted without any language or year restrictions, ensuring a wide-ranging exploration of the available literature. Additionally, the study followed updated PRISMA recommendations. Furthermore, it consisted largely in a time course analysis of HRV, HR and BP revealing the dynamics of autonomic and cardiovascular responses after cold exposure. This temporal perspective enhances comprehension of post-exposure physiological changes. Nevertheless, it is important to acknowledge that additional research is needed to ensure deeper understanding of the immediate and prolonged responses. Another strength is that our study explores the impact of cold exposure according to moderators on the concerned outcomes. While this perspective may help to understand the different reactions of
different groups, it is essential to note that analysis performed in smaller subgroups may
reduce our ability to detect statistically significant effects. Consequently, our meta-analysis
revealed a noteworthy gap in the current literature regarding the observed changes, according
to individual characteristics (sex, age, BMI, body fat percent), in cardiovascular and cardiac
autonomic control following cold exposure.

Notwithstanding the scientific interest raised by this meta-analysis, our work is not free of
limitations. Given the absence due to the cooling sensation felt by participants of a completely
blind procedure, quality assessment using the PEDro scale indicated a maximum score of 8.
Furthermore, all included studies presented good to medium methodological quality. In the
reviewed articles, only Fonda et al., (Fonda et al., 2014) and Muller al et al., (Muller et al.,
2012) conducted their investigation with an a priori power analysis. Therefore, it should be
advisable for authors in future studies to estimate appropriate sample size. Additionally, the
inclusion criteria in our review seem to be quite specific, focusing only on healthy participants
and excluding studies that incorporate physical activity to their protocols. This specificity may
limit the diversity of included studies. Due to the limited number of eligible studies, it was
necessary to include uncontrolled studies. Lastly, our work relied on data availability,
basically means and standard deviations, from the included studies. When studies did not
provide such data, they were excluded, limiting the number of included studies in our analysis.
Future studies should include information essential to effective data extraction.

References

Barwood, M.J., Corbett, J., Tipton, M., Wagstaff, C., Massey, H., 2017. Habituation of the cold shock response is inhibited by repeated anxiety: Implications for safety behaviour on accidental cold water immersions. Physiol. Behav. 174, 10–17. https://doi.org/10.1016/j.physbeh.2017.02.026

Barwood, M.J., Corbett, J., Wagstaff, C.R.D., 2014. Habituation of the Cold Shock Response May Include a Significant Perceptual Component. Aviat. Space. Environ. Med. 85, 167–171. https://doi.org/10.3357/ASEM.3759.2014

Bonde-Petersen, F., Schultz-Pedersen, L., Dragsted, N., 1992. Peripheral and central blood flow in man during cold, thermoneutral, and hot water immersion. Aviat. Space. Environ. Med. 63, 346–350.+

Borenstein, M., Hedges, L.V., Higgins, J.P.T., Rothstein, H.R., 2009. Introduction to Meta-Analysis. Chichester, UK: John Wiley & Sons.

Brazaitis, M., Eimantas, N., Daniuseviciute, L., Baranauskiene, N., Skrodeniene, E., Skurvydas, A., 2014. Time course of physiological and psychological responses in humans during a 20-day severe-cold-acclimation programme. PLoS One 9, e94698. https://doi.org/10.1371/journal.pone.0094698
different groups, it is essential to note that analysis performed in smaller subgroups may reduce our ability to detect statistically significant effects. Consequently, our meta-analysis revealed a noteworthy gap in the current literature regarding the observed changes, according to individual characteristics (sex, age, BMI, body fat percent), in cardiovascular and cardiac autonomic control following cold exposure.

Notwithstanding the scientific interest raised by this meta-analysis, our work is not free of limitations. Given the absence due to the cooling sensation felt by participants of a completely blind procedure, quality assessment using the PEDro scale indicated a maximum score of 8. Furthermore, all included studies presented good to medium methodological quality. In the reviewed articles, only Fonda et al., (Fonda et al., 2014) and Muller al et al., (Muller et al., 2012) conducted their investigation with an a priori power analysis. Therefore, it should be advisable for authors in future studies to estimate appropriate sample size. Additionally, the inclusion criteria in our review seem to be quite specific, focusing only on healthy participants and excluding studies that incorporate physical activity to their protocols. This specificity may limit the diversity of included studies. Due to the limited number of eligible studies, it was necessary to include uncontrolled studies. Lastly, our work relied on data availability, basically means and standard deviations, from the included studies. When studies did not provide such data, they were excluded, limiting the number of included studies in our analysis. Future studies should include information essential to effective data extraction.

## References

- Barwood, M.J., Corbett, J., Tipton, M., Wagstaff, C., Massey, H., 2017. Habituation of the cold shock response is inhibited by repeated anxiety: Implications for safety behaviour on accidental cold water immersions. Physiol. Behav. 174, 10–17. https://doi.org/10.1016/j.physbeh.2017.02.026

- Barwood, M.J., Corbett, J., Wagstaff, C.R.D., 2014. Habituation of the Cold Shock Response May Include a Significant Perceptual Component. Aviat. Space. Environ. Med. 85, 167–171. https://doi.org/10.3357/ASEM.3759.2014

- Bonde-Petersen, F., Schultz-Pedersen, L., Dragsted, N., 1992. Peripheral and central blood flow in man during cold, thermoneutral, and hot water immersion. Aviat. Space. Environ. Med. 63, 346–350.+

- Borenstein, M., Hedges, L.V., Higgins, J.P.T., Rothstein, H.R., 2009. Introduction to Meta-Analysis. Chichester, UK: John Wiley & Sons.

- Brazaitis, M., Eimantas, N., Daniuseviciute, L., Baranauskiene, N., Skrodeniene, E., Skurvydas, A., 2014. Time course of physiological and psychological responses in humans during a 20-day severe-cold-acclimation programme. PLoS One 9, e94698. https://doi.org/10.1371/journal.pone.0094698
Cohen, J., 1998. Statistical power analysis for the behavioral sciences. Lawrence Erlbaum Associates. Hillsdale, NJ 20-26.

Coppi, F., Pinti, M., Selleri, V., Zanini, G., D'Alisera, R., Latessa, P., Tripi, F., Savino, G., Cossarizza, A., Nasi, M., Mattioli, A., 2022. Cardiovascular Effects of Whole-Body Cryotherapy in Non-professional Athletes. Front. Cardiovasc. Med. 9. https://doi.org/10.3389/fcvm.2022.905790

Costello, J., Donnelly, A., Karki, A., Selfe, J., 2013. Effects of Whole Body Cryotherapy and Cold Water Immersion on Knee Skin Temperature. Int. J. Sports. Med. 35, 35-40. https://doi.org/10.1055/s-0033-1343410

Cuttell, S., Hammond, L., Langdon, D., Costello, J., 2017. Individualising the exposure of-110 degrees C whole body cryotherapy: The effects of sex and body composition. J. Therm. Biol. 65, 41-47. https://doi.org/10.1016/j.jtherbio.2017.01.014

Damijan, Z., Uhrynski, A., 2012. Systemic Cryotherapy Influence of Low Temperatures on Selected Physiological Parameters. Acta. Phys. Pol. A. 121, A38-A41.

Dębiec-Bąk, A., Skrzek, A., Podbielska, H., 2013. Application of thermovision for estimation of the optimal and safe parameters of the whole body cryotherapy. J. Therm. Anal. Calorim. 111, 1853-1859. https://doi.org/10.1007/s10973-012-2741-4

Douzi, W., Dupuy, O., Tanneau, M., Boucard, G., Bouzigon, R., Dugué, B., 2019a. 3-min whole body cryotherapy/cryostimulation after training in the evening improves sleep quality in physically active men. Eur. J. Sport. Sci. 19, 860-867. https://doi.org/10.1080/17461391.2018.1551937

Douzi, W., Dupuy, O., Theurot, D., Boucard, G., Dugué, B., 2019b. Partial-body cryostimulation after training improves sleep quality in professional soccer players. BMC Res. Notes 12, 141. https://doi.org/10.1186/s13104-019-4172-9

Douzi, W., Dupuy, O., Theurot, D., Smolander, J., Dugué, B., 2020. Per-Cooling (Using Cooling Systems during Physical Exercise) Enhances Physical and Cognitive Performances in Hot Environments. A Narrative Review. Int. J. Environ. Res. Public Health. 17, 1031. https://doi.org/10.3390/ijerph17031031

Drevon, D., Fursa, S.R., Malcolm, A.L., 2017. Intercoder Reliability and Validity of WebPlotDigitizer in Extracting Graphed Data. Behav. Modif. 41, 323-339. https://doi.org/10.1177/0145445516673998

Eimonte, M., Paulauskas, H., Daniuseviciute, L., Eimantas, N., Vitkauskiene, A., Dauksaite, G., Solianik, R., Brazaitis, M., 2021. Residual effects of short-term whole-body cold-water immersion on the cytokine profile, white blood cell count, and blood markers of stress. Int. J. Hyperthermia. 38, 696-707. https://doi.org/10.1080/02656736.2021.1915504

Fonda, B., De Nardi, M., Sarabon, N., 2014. Effects of whole-body cryotherapy duration on thermal and cardio-vascular response. J. Therm. Biol. 42, 52-55. https://doi.org/10.1016/j.jtherbio.2014.04.001

Fox, W.C., Hall, C., Hall, E., Kolkhorst, F., Lockette, W., 2003. Cardiovascular baroreceptors mediate susceptibility to hypothermia. Aviat. Space. Environ. Med. 74, 132-137.

Gregson, W., Black, M.A., Jones, H., Milson, J., Morton, J., Dawson, B., Atkinson, G., Green, D.J., 2011. Influence of Cold Water Immersion on Limb and Cutaneous Blood Flow at Rest. Am. J. Sports. Med. 39, 1316-1323. https://doi.org/10.1177/0363546510395497
Cohen, J., 1998. Statistical power analysis for the behavioral sciences. Lawrence Erlbaum Associates. Hillsdale, NJ 20-26.

Coppi, F., Pinti, M., Selleri, V., Zanini, G., D'Alisera, R., Latessa, P., Tripi, F., Savino, G., Cossarizza, A., Nasi, M., Mattioli, A., 2022. Cardiovascular Effects of Whole-Body Cryotherapy in Non-professional Athletes. Front. Cardiovasc. Med. 9. https://doi.org/10.3389/fcvm.2022.905790

Costello, J., Donnelly, A., Karki, A., Selfe, J., 2013. Effects of Whole Body Cryotherapy and Cold Water Immersion on Knee Skin Temperature. Int. J. Sports. Med. 35, 35-40. https://doi.org/10.1055/s-0033-1343410

Cuttell, S., Hammond, L., Langdon, D., Costello, J., 2017. Individualising the exposure of-110 degrees C whole body cryotherapy: The effects of sex and body composition. J. Therm. Biol. 65, 41-47. https://doi.org/10.1016/j.jtherbio.2017.01.014

Damijan, Z., Uhrynski, A., 2012. Systemic Cryotherapy Influence of Low Temperatures on Selected Physiological Parameters. Acta. Phys. Pol. A. 121, A38-A41.

Dębiec-Bąk, A., Skrzek, A., Podbielska, H., 2013. Application of thermovision for estimation of the optimal and safe parameters of the whole body cryotherapy. J. Therm. Anal. Calorim. 111, 1853-1859. https://doi.org/10.1007/s10973-012-2741-4

Douzi, W., Dupuy, O., Tanneau, M., Boucard, G., Bouzigon, R., Dugué, B., 2019a. 3-min whole body cryotherapy/cryostimulation after training in the evening improves sleep quality in physically active men. Eur. J. Sport. Sci. 19, 860-867. https://doi.org/10.1080/17461391.2018.1551937

Douzi, W., Dupuy, O., Theurot, D., Boucard, G., Dugué, B., 2019b. Partial-body cryostimulation after training improves sleep quality in professional soccer players. BMC Res. Notes 12, 141. https://doi.org/10.1186/s13104-019-4172-9

Douzi, W., Dupuy, O., Theurot, D., Smolander, J., Dugué, B., 2020. Per-Cooling (Using Cooling Systems during Physical Exercise) Enhances Physical and Cognitive Performances in Hot Environments. A Narrative Review. Int. J. Environ. Res. Public Health. 17, 1031. https://doi.org/10.3390/ijerph17031031

Drevon, D., Fursa, S.R., Malcolm, A.L., 2017. Intercoder Reliability and Validity of WebPlotDigitizer in Extracting Graphed Data. Behav. Modif. 41, 323-339. https://doi.org/10.1177/0145445516673998

Eimonte, M., Paulauskas, H., Daniuseviciute, L., Eimantas, N., Vitkauskiene, A., Dauksaite, G., Solianik, R., Brazaitis, M., 2021. Residual effects of short-term whole-body cold-water immersion on the cytokine profile, white blood cell count, and blood markers of stress. Int. J. Hyperthermia. 38, 696-707. https://doi.org/10.1080/02656736.2021.1915504

Fonda, B., De Nardi, M., Sarabon, N., 2014. Effects of whole-body cryotherapy duration on thermal and cardio-vascular response. J. Therm. Biol. 42, 52-55. https://doi.org/10.1016/j.jtherbio.2014.04.001

Fox, W.C., Hall, C., Hall, E., Kolkhorst, F., Lockette, W., 2003. Cardiovascular baroreceptors mediate susceptibility to hypothermia. Aviat. Space. Environ. Med. 74, 132-137.

Gregson, W., Black, M.A., Jones, H., Milson, J., Morton, J., Dawson, B., Atkinson, G., Green, D.J., 2011. Influence of Cold Water Immersion on Limb and Cutaneous Blood Flow at Rest. Am. J. Sports. Med. 39, 1316-1323. https://doi.org/10.1177/0363546510395497
Guolo, A., Varin, C., 2017. Random-effects meta-analysis: the number of studies matters. Stat. Methods. Med. Res. 26, 1500–1518. https://doi.org/10.1177/0962280215583568

Hammond, L., Mitchell, K., Cuttell, S., 2020. Ventilatory responses to whole body cryotherapy. J. Therm. Biol. 91, 102633. https://doi.org/10.1016/j.jtherbio.2020.102633

Harinath, K., Malhotra, A.S., Pal, K., Prasad, R., Kumar, R., Sawhney, R.C., 2005. Autonomic nervous system and adrenal response to cold in man at Antarctica. Wilderness. Environ. Med. 16, 81–91. https://doi.org/10.1580/pr30-04.1

Hausswirth, C., Schaal, K., Le Meur, Y., Bieuzen, F., Filliard, J.-R., Volondat, M., Louis, J., 2013. Parasympathetic Activity and Blood Catecholamine Responses Following a Single Partial-Body Cryostimulation and a Whole-Body Cryostimulation. PLoS ONE 8. https://doi.org/10.1371/journal.pone.0072658

Hayward, J.S., 1984. Thermal protection performance of survival suits in ice-water. Aviat. Space. Environ. Med. 55, 212–215.

Hayward, J.S., Eckerson, J.D., 1984. Physiological responses and survival time prediction for humans in ice-water. Aviat. Space. Environ. Med. 55, 206–211.

Hedges, L.V., 1981. Distribution Theory for Glass's Estimator of Effect size and Related Estimators. J. Educ. Stat. 6, 107–128. https://doi.org/10.3102/10769986006002107

Higgins, J.P.T., Thompson, S.G., Deeks, J.J., Altman, D.G., 2003. Measuring inconsistency in meta-analyses. BMJ 327, 557–560. https://doi.org/10.1136/bmj.327.7414.557

Hillebrand, S., de Mutsert, R., Christen, T., Maan, A.C., Jukema, J.W., Lamb, H.J., de Roos, A., Rosendaal, F.R., den Heijer, M., Swenne, C.A., NEO Study Group, 2014. Body fat, especially visceral fat, is associated with electrocardiographic measures of sympathetic activation. Obesity (Silver Spring) 22, 1553–1559. https://doi.org/10.1002/oby.20709

Jansky, L., Sramek, P., Savlikova, J., Ulicny, B., Janakova, H., Horky, K., 1996. Change in sympathetic activity, cardiovascular functions and plasma hormone concentrations due to cold water immersion in men. Eur. J. Appl. Physiol. 74, 148–152. https://doi.org/10.1007/BF00376507

Kwiecien, S.Y., McHugh, M.P., Goodall, S., Hicks, K.M., Hunter, A.M., Howatson, G., 2019. Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes From Cold-Water Immersion Versus Prolonged Cooling of Phase-Change Material. Int. J. Sports. Physiol. Perform. 14, 1288–1296. https://doi.org/10.1123/ijspp.2018-0763

Louis, J., Schaal, K., Bieuzen, F., Le Meur, Y., Filliard, J.-R., Volondat, M., Brisswalter, J., Hausswirth, C., 2015. Head Exposure to Cold during Whole-Body Cryostimulation: Influence on Thermal Response and Autonomic Modulation. Plos One 10, e0124776. https://doi.org/10.1371/journal.pone.0124776

Louis, J., Theurot, D., Filliard, J.-R., Volondat, M., Dugué, B., Dupuy, O., 2020. The use of whole-body cryotherapy: time- and dose-response investigation on circulating blood catecholamines and heart rate variability. Eur. J. Appl. Physiol. 120, 1733–1743. https://doi.org/10.1007/s00421-020-04406-5

Lukowska, A., Suska, M., 2011. The increase in systolic and diastolic blood pressure after exposure to cryogenic temperatures in normotensive men as a contraindication for whole-body cryostimulation. J. Therm. Biol. 36, 264–268. https://doi.org/10.1016/j.jtherbio.2011.03.011
Guolo, A., Varin, C., 2017. Random-effects meta-analysis: the number of studies matters. Stat. Methods. Med. Res. 26, 1500–1518. https://doi.org/10.1177/0962280215583568

Hammond, L., Mitchell, K., Cuttell, S., 2020. Ventilatory responses to whole body cryotherapy. J. Therm. Biol. 91, 102633. https://doi.org/10.1016/j.jtherbio.2020.102633

Harinath, K., Malhotra, A.S., Pal, K., Prasad, R., Kumar, R., Sawhney, R.C., 2005. Autonomic nervous system and adrenal response to cold in man at Antarctica. Wilderness. Environ. Med. 16, 81–91. https://doi.org/10.1580/pr30-04.1

Hausswirth, C., Schaal, K., Le Meur, Y., Bieuzen, F., Filliard, J.-R., Volondat, M., Louis, J., 2013. Parasympathetic Activity and Blood Catecholamine Responses Following a Single Partial-Body Cryostimulation and a Whole-Body Cryostimulation. PLoS ONE 8. https://doi.org/10.1371/journal.pone.0072658

Hayward, J.S., 1984. Thermal protection performance of survival suits in ice-water. Aviat. Space. Environ. Med. 55, 212–215.

Hayward, J.S., Eckerson, J.D., 1984. Physiological responses and survival time prediction for humans in ice-water. Aviat. Space. Environ. Med. 55, 206–211.

Hedges, L.V., 1981. Distribution Theory for Glass's Estimator of Effect size and Related Estimators. J. Educ. Stat. 6, 107–128. https://doi.org/10.3102/10769986006002107

Higgins, J.P.T., Thompson, S.G., Deeks, J.J., Altman, D.G., 2003. Measuring inconsistency in meta-analyses. BMJ 327, 557–560. https://doi.org/10.1136/bmj.327.7414.557

Hillebrand, S., de Mutsert, R., Christen, T., Maan, A.C., Jukema, J.W., Lamb, H.J., de Roos, A., Rosendaal, F.R., den Heijer, M., Swenne, C.A., NEO Study Group, 2014. Body fat, especially visceral fat, is associated with electrocardiographic measures of sympathetic activation. Obesity (Silver Spring) 22, 1553–1559. https://doi.org/10.1002/oby.20709

Jansky, L., Sramek, P., Savlikova, J., Ulicny, B., Janakova, H., Horky, K., 1996. Change in sympathetic activity, cardiovascular functions and plasma hormone concentrations due to cold water immersion in men. Eur. J. Appl. Physiol. 74, 148–152. https://doi.org/10.1007/BF00376507

Kwiecien, S.Y., McHugh, M.P., Goodall, S., Hicks, K.M., Hunter, A.M., Howatson, G., 2019. Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes From Cold-Water Immersion Versus Prolonged Cooling of Phase-Change Material. Int. J. Sports. Physiol. Perform. 14, 1288–1296. https://doi.org/10.1123/ijspp.2018-0763

Louis, J., Schaal, K., Bieuzen, F., Le Meur, Y., Filliard, J.-R., Volondat, M., Brisswalter, J., Hausswirth, C., 2015. Head Exposure to Cold during Whole-Body Cryostimulation: Influence on Thermal Response and Autonomic Modulation. Plos One 10, e0124776. https://doi.org/10.1371/journal.pone.0124776

Louis, J., Theurot, D., Filliard, J.-R., Volondat, M., Dugué, B., Dupuy, O., 2020. The use of whole-body cryotherapy: time- and dose-response investigation on circulating blood catecholamines and heart rate variability. Eur. J. Appl. Physiol. 120, 1733–1743. https://doi.org/10.1007/s00421-020-04406-5

Lukowska, A., Suska, M., 2011. The increase in systolic and diastolic blood pressure after exposure to cryogenic temperatures in normotensive men as a contraindication for whole-body cryostimulation. J. Therm. Biol. 36, 264–268. https://doi.org/10.1016/j.jtherbio.2011.03.011
Lubkowska, A., Szyguła, Z., 2010. Changes in blood pressure with compensatory heart rate decrease and in the level of aerobic capacity in response to repeated whole-body cryostimulation in normotensive, young and physically active men. Int. J. Occup. Med. Environ. Health. 23, 367-375. https://doi.org/10.2478/v10001-010-0037-0

Machado, A.F., Ferreira, P.H., Micheletti, J.K., de Almeida, A.C., Lemes, Í.R., Vanderlei, F.M., Netto Junior, J., Pastre, C.M., 2016. Can Water Temperature and Immersion Time Influence the Effect of Cold Water Immersion on Muscle Soreness? A Systematic Review and Meta-Analysis. Sports. Med. 46, 503-514. https://doi.org/10.1007/s40279-015-0431-7

Maher, C.G., Sherrington, C., Herbert, R.D., Moseley, A.M., Elkins, M., 2003. Reliability of the PEDro scale for rating quality of randomized controlled trials. Phys. Ther. 83, 713-721.

Mäkinen, T.M., Mäntysaari, M., Pääkkönen, T., Jokelainen, J., Palinkas, L.A., Hassi, J., Leppäluoto, J., Tahvanainen, K., Rintamäki, H., 2008. Autonomic Nervous Function During Whole-Body Cold Exposure Before and After Cold Acclimation. Aviat. Space. Environ. Med. 79, 875-882. https://doi.org/10.3357/ASEM.2235.2008

Malik, M., 1996. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Ann. Noninvasive Electrocardiol 1, 151-181. https://doi.org/10.1111/j.1542-474X.1996.tb00275.x

Mantoni, T., Belhage, B., Pedersen, L.M., Pott, F.C., 2007. Reduced cerebral perfusion on sudden immersion in ice water: A possible cause of drowning. Aviat. Space. Environ. Med. 78, 374-376.

Mantoni, T., Rasmussen, J.H., Belhage, B., Pott, F.C., 2008. Voluntary respiratory control and cerebral blood flow velocity upon ice-water immersion. Aviat. Space. Environ. Med. 79, 765-768. https://doi.org/10.3357/ASEM.2216.2008

Master, A., 1950. The normal blood pressure range and its clinical implications. J. Am. Med. Assoc. 143, 1464. https://doi.org/10.1001/jama.1950.02910520006004

Mawhinney, C., Heinonen, I., Low, D.A., Han, C., Jones, H., Kalliokoski, K.K., Kirjavainen, A., Kemppainen, J., Di Salvo, V., Weston, M., Cable, T., Gregson, W., 2020. Changes in quadriceps femoris muscle perfusion following different degrees of cold-water immersion. J. Appl. Physiol. 128, 1392-1401. https://doi.org/10.1152/japplphysiol.00833.2019

Moore, E., Fuller, J.T., Bellenger, C.R., Saunders, S., Halson, S.L., Broatch, J.R., Buckley, J.D., 2023. Effects of Cold-Water Immersion Compared with Other Recovery Modalities on Athletic Performance Following Acute Strenuous Exercise in Physically Active Participants: A Systematic Review, Meta-Analysis, and Meta-Regression. Sports. Med. 53, 687-705. https://doi.org/10.1007/s40279-022-01800-1

Muller, M.D., Kim, C.-H., Seo, Y., Ryan, E.J., Glickman, E.L., 2012. Hemodynamic and Thermoregulatory Responses to Lower Body Water Immersion. Aviat. Space. Environ. Med. 83, 935-941. https://doi.org/10.3357/ASEM.3311.2012

Neal, B.S., Barton, C.J., Gallie, R., O'Halloran, P., Morrissey, D., 2016. Runners with patellofemoral pain have altered biomechanics which targeted interventions can modify:
Lubkowska, A., Szyguła, Z., 2010. Changes in blood pressure with compensatory heart rate decrease and in the level of aerobic capacity in response to repeated whole-body cryostimulation in normotensive, young and physically active men. Int. J. Occup. Med. Environ. Health. 23, 367-375. https://doi.org/10.2478/v10001-010-0037-0

Machado, A.F., Ferreira, P.H., Micheletti, J.K., de Almeida, A.C., Lemes, Í.R., Vanderlei, F.M., Netto Junior, J., Pastre, C.M., 2016. Can Water Temperature and Immersion Time Influence the Effect of Cold Water Immersion on Muscle Soreness? A Systematic Review and Meta-Analysis. Sports. Med. 46, 503-514. https://doi.org/10.1007/s40279-015-0431-7

Maher, C.G., Sherrington, C., Herbert, R.D., Moseley, A.M., Elkins, M., 2003. Reliability of the PEDro scale for rating quality of randomized controlled trials. Phys. Ther. 83, 713-721.

Mäkinen, T.M., Mäntysaari, M., Pääkkönen, T., Jokelainen, J., Palinkas, L.A., Hassi, J., Leppäluoto, J., Tahvanainen, K., Rintamäki, H., 2008. Autonomic Nervous Function During Whole-Body Cold Exposure Before and After Cold Acclimation. Aviat. Space. Environ. Med. 79, 875-882. https://doi.org/10.3357/ASEM.2235.2008

Malik, M., 1996. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Ann. Noninvasive Electrocardiol 1, 151-181. https://doi.org/10.1111/j.1542-474X.1996.tb00275.x

Mantoni, T., Belhage, B., Pedersen, L.M., Pott, F.C., 2007. Reduced cerebral perfusion on sudden immersion in ice water: A possible cause of drowning. Aviat. Space. Environ. Med. 78, 374-376.

Mantoni, T., Rasmussen, J.H., Belhage, B., Pott, F.C., 2008. Voluntary respiratory control and cerebral blood flow velocity upon ice-water immersion. Aviat. Space. Environ. Med. 79, 765-768. https://doi.org/10.3357/ASEM.2216.2008

Master, A., 1950. The normal blood pressure range and its clinical implications. J. Am. Med. Assoc. 143, 1464. https://doi.org/10.1001/jama.1950.02910520006004

Mawhinney, C., Heinonen, I., Low, D.A., Han, C., Jones, H., Kalliokoski, K.K., Kirjavainen, A., Kemppainen, J., Di Salvo, V., Weston, M., Cable, T., Gregson, W., 2020. Changes in quadriceps femoris muscle perfusion following different degrees of cold-water immersion. J. Appl. Physiol. 128, 1392-1401. https://doi.org/10.1152/japplphysiol.00833.2019

Moore, E., Fuller, J.T., Bellenger, C.R., Saunders, S., Halson, S.L., Broatch, J.R., Buckley, J.D., 2023. Effects of Cold-Water Immersion Compared with Other Recovery Modalities on Athletic Performance Following Acute Strenuous Exercise in Physically Active Participants: A Systematic Review, Meta-Analysis, and Meta-Regression. Sports. Med. 53, 687-705. https://doi.org/10.1007/s40279-022-01800-1

Muller, M.D., Kim, C.-H., Seo, Y., Ryan, E.J., Glickman, E.L., 2012. Hemodynamic and Thermoregulatory Responses to Lower Body Water Immersion. Aviat. Space. Environ. Med. 83, 935-941. https://doi.org/10.3357/ASEM.3311.2012

Neal, B.S., Barton, C.J., Gallie, R., O'Halloran, P., Morrissey, D., 2016. Runners with patellofemoral pain have altered biomechanics which targeted interventions can modify:
A systematic review and meta-analysis. Gait Posture 45, 69-82.
https://doi.org/10.1016/j.gaitpost.2015.11.018

Nunan, D., Sandercock, G.R.H., Brodie, D.A., 2010. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing Clin. Electrophysiol 33, 1407-1417. https://doi.org/10.1111/j.1540-8159.2010.02841.x

O'Brien, C., Young, A.J., Lee, D.T., Shitzer, A., Sawka, M.N., Pandolf, K.B., 2000. Role of core temperature as a stimulus for cold acclimation during repeated immersion in 20 degrees C water. J. Appl. Physiol. 89, 242-250.
https://doi.org/10.1152/jappl.2000.89.1.242

Ouzzani, M., Hammady, H., Fedorowicz, Z., Elmagarmid, A., 2016. Rayyan—a web and mobile app for systematic reviews. Syst. Rev. 5, 210. https://doi.org/10.1186/s13643-016-0384-4

Page, M.J., McKenzie, J.E., Bossuyt, P.M., Boutron, I., Hoffmann, T.C., Mulrow, C.D., Shamseer, L., Tetzlaff, J.M., Akl, E.A., Brennan, S.E., Chou, R., Glanville, J., Grimshaw, J.M., Hróbjartsson, A., Lalu, M.M., Li, T., Loder, E.W., Mayo-Wilson, E., McDonald, S., McGuinness, L.A., Stewart, L.A., Thomas, J., Tricco, A.C., Welch, V.A., Whiting, P., Moher, D., 2021. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 372, n71. https://doi.org/10.1136/bmj.n71

Pump, B., Shiraishi, M., Gabrielsen, A., Bie, P., Christensen, N.J., Norsk, P., 2001. Cardiovascular effects of static carotid baroreceptor stimulation during water immersion in humans. Am. J. Physiol. Heart. Circ. Physiol. 280, H2607-2615.
https://doi.org/10.1152/ajpheart.2001.280.6.H2607

Ramaekers, D., 1998. Heart rate variability and heart rate in healthy volunteers. Is the female autonomic nervous system cardioprotective? Eur. Heart. J. 19, 1334-1341.
https://doi.org/10.1053/euhj.1998.1084

Reutersberg, B., Pelisek, J., Rössler, F., Ouda, A., Rougemont, O., Zimmermann, A., 2022. Baroreceptors in the Aortic Arch and Their Potential Role in Aortic Dissection and Aneurysms. J. Clin. Med. 11. https://doi.org/10.3390/jcm11051161

Rose, C.L., McGuire, H., Graham, K., Siegler, J., de St Groth, B.F., Caillaud, C., Edwards, K.M., 2023. Partial body cryotherapy exposure drives acute redistribution of circulating lymphocytes: preliminary findings. Eur. J. Appl. Physiol. 123, 407-415.
https://doi.org/10.1007/s00421-022-05058-3

Shaffer, F., Ginsberg, J.P., 2017. An Overview of Heart Rate Variability Metrics and Norms. Front. Public Health 5, 258. https://doi.org/10.3389/fpubh.2017.00258

Sramek, P., Simeckova, M., Jansky, L., Savlikova, J., Vybiral, S., 2000. Human physiological responses to immersion into water of different temperatures. Eur. J. Appl. Physiol. 81, 436-442. https://doi.org/10.1007/s004210050065

Sztajzel, J., 2004. Heart rate variability: a noninvasive electrocardiographic method to measure the autonomic nervous system. Swiss. Med. Wkly. 134, 514-522.
https://doi.org/10.4414/smw.2004.10321

Theurot, D., Dugué, B., Douzi, W., Guitet, P., Louis, J., Dupuy, O., 2021. Impact of acute partial-body cryostimulation on cognitive performance, cerebral oxygenation, and cardiac autonomic activity. Sci. Rep. 11, 7793. https://doi.org/10.1038/s41598-021-87089-y
A systematic review and meta-analysis. Gait Posture 45, 69-82.
https://doi.org/10.1016/j.gaitpost.2015.11.018

Nunan, D., Sandercock, G.R.H., Brodie, D.A., 2010. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing Clin. Electrophysiol 33, 1407-1417. https://doi.org/10.1111/j.1540-8159.2010.02841.x

O'Brien, C., Young, A.J., Lee, D.T., Shitzer, A., Sawka, M.N., Pandolf, K.B., 2000. Role of core temperature as a stimulus for cold acclimation during repeated immersion in 20 degrees C water. J. Appl. Physiol. 89, 242-250.
https://doi.org/10.1152/jappl.2000.89.1.242

Ouzzani, M., Hammady, H., Fedorowicz, Z., Elmagarmid, A., 2016. Rayyan—a web and mobile app for systematic reviews. Syst. Rev. 5, 210. https://doi.org/10.1186/s13643-016-0384-4

Page, M.J., McKenzie, J.E., Bossuyt, P.M., Boutron, I., Hoffmann, T.C., Mulrow, C.D., Shamseer, L., Tetzlaff, J.M., Akl, E.A., Brennan, S.E., Chou, R., Glanville, J., Grimshaw, J.M., Hróbjartsson, A., Lalu, M.M., Li, T., Loder, E.W., Mayo-Wilson, E., McDonald, S., McGuinness, L.A., Stewart, L.A., Thomas, J., Tricco, A.C., Welch, V.A., Whiting, P., Moher, D., 2021. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 372, n71. https://doi.org/10.1136/bmj.n71

Pump, B., Shiraishi, M., Gabrielsen, A., Bie, P., Christensen, N.J., Norsk, P., 2001. Cardiovascular effects of static carotid baroreceptor stimulation during water immersion in humans. Am. J. Physiol. Heart. Circ. Physiol. 280, H2607-2615.
https://doi.org/10.1152/ajpheart.2001.280.6.H2607

Ramaekers, D., 1998. Heart rate variability and heart rate in healthy volunteers. Is the female autonomic nervous system cardioprotective? Eur. Heart. J. 19, 1334-1341.
https://doi.org/10.1053/euhj.1998.1084

Reutersberg, B., Pelisek, J., Rössler, F., Ouda, A., Rougemont, O., Zimmermann, A., 2022. Baroreceptors in the Aortic Arch and Their Potential Role in Aortic Dissection and Aneurysms. J. Clin. Med. 11. https://doi.org/10.3390/jcm11051161

Rose, C.L., McGuire, H., Graham, K., Siegler, J., de St Groth, B.F., Caillaud, C., Edwards, K.M., 2023. Partial body cryotherapy exposure drives acute redistribution of circulating lymphocytes: preliminary findings. Eur. J. Appl. Physiol. 123, 407-415.
https://doi.org/10.1007/s00421-022-05058-3

Shaffer, F., Ginsberg, J.P., 2017. An Overview of Heart Rate Variability Metrics and Norms. Front. Public Health 5, 258. https://doi.org/10.3389/fpubh.2017.00258

Sramek, P., Simeckova, M., Jansky, L., Savlikova, J., Vybiral, S., 2000. Human physiological responses to immersion into water of different temperatures. Eur. J. Appl. Physiol. 81, 436-442. https://doi.org/10.1007/s004210050065

Sztajzel, J., 2004. Heart rate variability: a noninvasive electrocardiographic method to measure the autonomic nervous system. Swiss. Med. Wkly. 134, 514-522.
https://doi.org/10.4414/smw.2004.10321

Theurot, D., Dugué, B., Douzi, W., Guitet, P., Louis, J., Dupuy, O., 2021. Impact of acute partial-body cryostimulation on cognitive performance, cerebral oxygenation, and cardiac autonomic activity. Sci. Rep. 11, 7793. https://doi.org/10.1038/s41598-021-87089-y
Tipton, M.J., Golden, F.S., 1987. The influence of regional insulation on the initial responses to cold immersion. Aviat. Space. Environ. Med. 58, 1192-1196.

Tipton, M.J., Golden, F.S., Higenbottam, C., Mekjavic, I.B., Eglin, C.M., 1998. Temperature dependence of habituation of the initial responses to cold-water immersion. Eur. J. Appl. Physiol. Occup. Physiol. 78, 253-257. https://doi.org/10.1007/s004210050416

Tipton, M.J., Mekjavic, I.B., Eglin, C.M., 2000. Permanence of the habituation of the initial responses to cold-water immersion in humans. Eur. J. Appl. Physiol. 83, 17-21. https://doi.org/10.1007/s004210000255

Udo, T., Mun, E.-Y., Buckman, J.F., Vaschillo, E.G., Vaschillo, B., Bates, M.E., 2013. Potential Side Effects of Unhealthy Lifestyle Choices and Health Risks on Basal and Reactive Heart Rate Variability in College Drinkers. J. Stud. Alcohol Drugs 74, 787-796. https://doi.org/10.15288/jsad.2013.74.787

van Ravenswaaij-Arts, C.M., Kollée, L.A., Hopman, J.C., Stoelinga, G.B., van Geijn, H.P., 1993. Heart rate variability. Ann. Intern. Med. 118, 436-447. https://doi.org/10.7326/0003-4819-118-6-199303150-00008

Versteeg, N., Clijsen, R., Hohenauer, E., 2023. Effects of 3-week repeated cold water immersion on leukocyte counts and cardiovascular factors: an exploratory study. Front. Physiol. 14, 1197585. https://doi.org/10.3389/fphys.2023.1197585

Vogelaere, P., Deklunder, G., Lecroart, J., 1995. Cardiac output variations in supine resting subjects during head-out cold water immersion. Int. J. Biometeorol 39, 40-45. https://doi.org/10.1007/BF01320892

Westerlund, T., Oksa, J., Smolander, J., Mikkelsson, M., 2003. Thermal responses during and after whole-body cryotherapy (-110°C). J. Therm. Biol. 28, 601-608. https://doi.org/10.1016/j.jtherbio.2003.08.006

Westerlund, T., Smolander, J., Uusitalo-Koskinen, A., Mikkelsson, M., 2004. The blood pressure responses to an acute and long-term whole-body cryotherapy (-110°C) in men and women. J. Therm. Biol. 29, 285-290. https://doi.org/10.1016/j.jtherbio.2004.05.004

Westerlund, T., Uusitalo, A., Smolander, J., Mikkelsson, M., 2006. Heart rate variability in women exposed to very cold air (-110°C) during whole-body cryotherapy. J. Therm. Biol. 31, 342-346. https://doi.org/10.1016/j.jtherbio.2006.01.004

Yugar, L.B.T., Yugar-Toledo, J.C., Dinamarco, N., Sedenho-Prado, L.G., Moreno, B.V.D., Rubio, T. de A., Fattori, A., Rodrigues, B., Vilela-Martin, J.F., Moreno, H., 2023. The Role of Heart Rate Variability (HRV) in Different Hypertensive Syndromes. Diagnostics 13, 785. https://doi.org/10.3390/diagnostics13040785

Zalewski, P., Bitner, A., Słomko, J., Szrajda, J., Klawe, J.J., Tafil-Klawe, M., Newton, J.L., 2014a. Whole-body cryostimulation increases parasympathetic outflow and decreases core body temperature. J. Therm. Biol. 45, 75-80. https://doi.org/10.1016/j.jtherbio.2014.08.001

Zalewski, P., Buszko, K., Zawadka-Kunikowska, M., Słomko, J., Szrajda, J., Klawe, J.J., Tafil-Klawe, M., Sinski, M., Newton, J., 2014b. Cardiovascular and autonomic responses to whole-body cryostimulation in essential hypertension. Cryobiology 69, 249-255. https://doi.org/10.1016/j.cryobiol.2014.07.014
Tipton, M.J., Golden, F.S., 1987. The influence of regional insulation on the initial responses to cold immersion. Aviat. Space. Environ. Med. 58, 1192-1196.

Tipton, M.J., Golden, F.S., Higenbottam, C., Mekjavic, I.B., Eglin, C.M., 1998. Temperature dependence of habituation of the initial responses to cold-water immersion. Eur. J. Appl. Physiol. Occup. Physiol. 78, 253-257. https://doi.org/10.1007/s004210050416

Tipton, M.J., Mekjavic, I.B., Eglin, C.M., 2000. Permanence of the habituation of the initial responses to cold-water immersion in humans. Eur. J. Appl. Physiol. 83, 17-21. https://doi.org/10.1007/s004210000255

Udo, T., Mun, E.-Y., Buckman, J.F., Vaschillo, E.G., Vaschillo, B., Bates, M.E., 2013. Potential Side Effects of Unhealthy Lifestyle Choices and Health Risks on Basal and Reactive Heart Rate Variability in College Drinkers. J. Stud. Alcohol Drugs 74, 787-796. https://doi.org/10.15288/jsad.2013.74.787

van Ravenswaaij-Arts, C.M., Kollée, L.A., Hopman, J.C., Stoelinga, G.B., van Geijn, H.P., 1993. Heart rate variability. Ann. Intern. Med. 118, 436-447. https://doi.org/10.7326/0003-4819-118-6-199303150-00008

Versteeg, N., Clijsen, R., Hohenauer, E., 2023. Effects of 3-week repeated cold water immersion on leukocyte counts and cardiovascular factors: an exploratory study. Front. Physiol. 14, 1197585. https://doi.org/10.3389/fphys.2023.1197585

Vogelaere, P., Deklunder, G., Lecroart, J., 1995. Cardiac output variations in supine resting subjects during head-out cold water immersion. Int. J. Biometeorol 39, 40-45. https://doi.org/10.1007/BF01320892

Westerlund, T., Oksa, J., Smolander, J., Mikkelsson, M., 2003. Thermal responses during and after whole-body cryotherapy (-110°C). J. Therm. Biol. 28, 601-608. https://doi.org/10.1016/j.jtherbio.2003.08.006

Westerlund, T., Smolander, J., Uusitalo-Koskinen, A., Mikkelsson, M., 2004. The blood pressure responses to an acute and long-term whole-body cryotherapy (-110°C) in men and women. J. Therm. Biol. 29, 285-290. https://doi.org/10.1016/j.jtherbio.2004.05.004

Westerlund, T., Uusitalo, A., Smolander, J., Mikkelsson, M., 2006. Heart rate variability in women exposed to very cold air (-110°C) during whole-body cryotherapy. J. Therm. Biol. 31, 342-346. https://doi.org/10.1016/j.jtherbio.2006.01.004

Yugar, L.B.T., Yugar-Toledo, J.C., Dinamarco, N., Sedenho-Prado, L.G., Moreno, B.V.D., Rubio, T. de A., Fattori, A., Rodrigues, B., Vilela-Martin, J.F., Moreno, H., 2023. The Role of Heart Rate Variability (HRV) in Different Hypertensive Syndromes. Diagnostics 13, 785. https://doi.org/10.3390/diagnostics13040785

Zalewski, P., Bitner, A., Słomko, J., Szrajda, J., Klawe, J.J., Tafil-Klawe, M., Newton, J.L., 2014a. Whole-body cryostimulation increases parasympathetic outflow and decreases core body temperature. J. Therm. Biol. 45, 75-80. https://doi.org/10.1016/j.jtherbio.2014.08.001

Zalewski, P., Buszko, K., Zawadka-Kunikowska, M., Słomko, J., Szrajda, J., Klawe, J.J., Tafil-Klawe, M., Sinski, M., Newton, J., 2014b. Cardiovascular and autonomic responses to whole-body cryostimulation in essential hypertension. Cryobiology 69, 249-255. https://doi.org/10.1016/j.cryobiol.2014.07.014
Zalewski, P., Klawe, J.J., Pawlak, J., Tafil-Klawe, M., Newton, J., 2013. Thermal and hemodynamic response to whole-body cryostimulation in healthy subjects. Cryobiology 66, 295-302. https://doi.org/10.1016/j.cryobiol.2013.03.006

Zhang, Z., Liang, L., Hou, X., 2003. Effect of cold stress on the rectal perception and autonomic nerve function in healthy subjects. Chin. J. Gastroenterol. 8, 221-223.
Zalewski, P., Klawe, J.J., Pawlak, J., Tafil-Klawe, M., Newton, J., 2013. Thermal and hemodynamic response to whole-body cryostimulation in healthy subjects. Cryobiology 66, 295-302. https://doi.org/10.1016/j.cryobiol.2013.03.006

Zhang, Z., Liang, L., Hou, X., 2003. Effect of cold stress on the rectal perception and autonomic nerve function in healthy subjects. Chin. J. Gastroenterol. 8, 221-223.
Supplementary Material
Supplementary Material
<table><caption>**Appendix 1. List of excluded articles after full text screening.**</caption><thead><tr><td>Studies</td><td>Reasons of exclusion</td></tr></thead><tbody><tr><td>■ Damijan and Uhrynski, 2012</td><td>■ Outcomes of interest not addressed</td></tr><tr><td>■ Tipton et al., 2000</td><td rowspan="5">■ Absence of pre- and post-intervention outcome measurements (Measurements was conducted only during cold water immersion).</td></tr><tr><td>■ Tipton et al., 1998</td></tr><tr><td>■ Barwood et al., 2017</td></tr><tr><td>■ Bonde-Petersen et al., 1992</td></tr><tr><td>■ Fox et al., 2003</td></tr><tr><td>■ O'Brien et al., 2000</td><td>■ Irrelevant cooling technique (cold air exposure at 5°C)</td></tr><tr><td>■ Gregson et al., 2011</td><td>■ Non-continuous cold water immersion technique</td></tr><tr><td>■ Versteeg et al., 2023</td><td>■ Not measured outcomes on acute intervention session</td></tr><tr><td>■ Hayward, 1984</td><td>■ Irrelevant cooling technique (the use of survival suits during cold water immersion)</td></tr><tr><td>■ Hayward and Eckerson, 1984</td><td rowspan="2">■ Absence of post-intervention outcome measurement (Measurement was conducted during cold water immersion).</td></tr><tr><td>■ Tipton and Golden, 1987</td></tr><tr><td>■ Zhang et al., 2003</td><td>■ Irrelevant cooling technique (hand cold-water immersion)</td></tr></tbody></table>
<table><caption>**Appendix 1. List of excluded articles after full text screening.**</caption><thead><tr><td>Studies</td><td>Reasons of exclusion</td></tr></thead><tbody><tr><td>■ Damijan and Uhrynski, 2012</td><td>■ Outcomes of interest not addressed</td></tr><tr><td>■ Tipton et al., 2000</td><td rowspan="5">■ Absence of pre- and post-intervention outcome measurements (Measurements was conducted only during cold water immersion).</td></tr><tr><td>■ Tipton et al., 1998</td></tr><tr><td>■ Barwood et al., 2017</td></tr><tr><td>■ Bonde-Petersen et al., 1992</td></tr><tr><td>■ Fox et al., 2003</td></tr><tr><td>■ O'Brien et al., 2000</td><td>■ Irrelevant cooling technique (cold air exposure at 5°C)</td></tr><tr><td>■ Gregson et al., 2011</td><td>■ Non-continuous cold water immersion technique</td></tr><tr><td>■ Versteeg et al., 2023</td><td>■ Not measured outcomes on acute intervention session</td></tr><tr><td>■ Hayward, 1984</td><td>■ Irrelevant cooling technique (the use of survival suits during cold water immersion)</td></tr><tr><td>■ Hayward and Eckerson, 1984</td><td rowspan="2">■ Absence of post-intervention outcome measurement (Measurement was conducted during cold water immersion).</td></tr><tr><td>■ Tipton and Golden, 1987</td></tr><tr><td>■ Zhang et al., 2003</td><td>■ Irrelevant cooling technique (hand cold-water immersion)</td></tr></tbody></table>
Appendix 2. Forest plots

<figure><img src="image_13.png" /></figure>
Appendix 2. Forest plots

<table><thead><tr><th rowspan="2">Study name</th><th rowspan="2">Std diff in means</th><th rowspan="2">Standard error</th><th colspan="4">Statistics for each study</th><th rowspan="2">Z-Value</th><th rowspan="2">p-Value</th></tr><tr><th>Variance</th><th>Upper limit</th><th>Lower limit</th></tr></thead><tbody><tr><td>Theurot et al., 2021 (1)</td><td>-1.154</td><td>0.430</td><td>0.185</td><td>-0.311</td><td>-1.997</td><td>-2.682</td><td>0.007</td></tr><tr><td>Theurot et al., 2021 (2)</td><td>-0.894</td><td>0.394</td><td>0.156</td><td>-0.121</td><td>-1.667</td><td>-2.268</td><td>0.023</td></tr><tr><td>Theurot et al., 2021 (3)</td><td>-1.041</td><td>0.293</td><td>0.086</td><td>-0.468</td><td>-1.615</td><td>-3.557</td><td>0.000</td></tr><tr><td>Hausswirth et al., 2012 (1)</td><td>-1.167</td><td>0.335</td><td>0.112</td><td>-0.511</td><td>-1.824</td><td>-3.487</td><td>0.000</td></tr><tr><td>Hausswirth et al., 2012 (2)</td><td>-0.799</td><td>0.297</td><td>0.088</td><td>-0.218</td><td>-1.380</td><td>-2.694</td><td>0.007</td></tr><tr><td>Hammond et al., 2020 (1)</td><td>-0.036</td><td>0.333</td><td>0.111</td><td>0.617</td><td>-0.690</td><td>-0.109</td><td>0.913</td></tr><tr><td>Hammond et al., 2020 (2)</td><td>0.529</td><td>0.378</td><td>0.143</td><td>1.269</td><td>-0.211</td><td>1.402</td><td>0.161</td></tr><tr><td>Hammond et al., 2020 (3)</td><td>0.284</td><td>0.247</td><td>0.061</td><td>0.769</td><td>-0.201</td><td>1.148</td><td>0.251</td></tr><tr><td>Louis et al., 2015 (1)</td><td>-0.100</td><td>0.317</td><td>0.100</td><td>0.521</td><td>-0.721</td><td>-0.315</td><td>0.752</td></tr><tr><td>Louis et al., 2015 (2)</td><td>-0.734</td><td>0.356</td><td>0.127</td><td>-0.036</td><td>-1.432</td><td>-2.060</td><td>0.039</td></tr><tr><td>Louis et al., 2015 (3)</td><td>-0.674</td><td>0.350</td><td>0.123</td><td>0.013</td><td>-1.360</td><td>-1.923</td><td>0.054</td></tr><tr><td>Louis et al., 2015 (4)</td><td>-0.532</td><td>0.338</td><td>0.114</td><td>0.130</td><td>-1.194</td><td>-1.574</td><td>0.116</td></tr><tr><td>Cuttell et al., 2017 (1)</td><td>0.264</td><td>0.322</td><td>0.103</td><td>0.895</td><td>-0.366</td><td>0.821</td><td>0.412</td></tr><tr><td>Cuttell et al., 2017 (2)</td><td>0.000</td><td>0.316</td><td>0.100</td><td>0.620</td><td>-0.620</td><td>0.000</td><td>1.000</td></tr><tr><td>Cuttell et al., 2017 (3)</td><td>-0.173</td><td>0.319</td><td>0.102</td><td>0.451</td><td>-0.798</td><td>-0.544</td><td>0.586</td></tr><tr><td>Cuttell et al., 2017 (4)</td><td>-0.087</td><td>0.317</td><td>0.100</td><td>0.534</td><td>-0.708</td><td>-0.274</td><td>0.784</td></tr><tr><td>Cuttell et al., 2017 (5)</td><td>0.000</td><td>0.316</td><td>0.100</td><td>0.620</td><td>-0.620</td><td>0.000</td><td>1.000</td></tr><tr><td>Cuttell et al., 2017 (6)</td><td>-0.085</td><td>0.317</td><td>0.100</td><td>0.536</td><td>-0.706</td><td>-0.268</td><td>0.789</td></tr><tr><td>Cuttell et al., 2017 (7)</td><td>0.000</td><td>0.316</td><td>0.100</td><td>0.620</td><td>-0.620</td><td>0.000</td><td>1.000</td></tr><tr><td>Cuttell et al., 2017 (8)</td><td>-0.089</td><td>0.317</td><td>0.100</td><td>0.532</td><td>-0.710</td><td>-0.280</td><td>0.779</td></tr><tr><td>Cuttell et al., 2017 (9)</td><td>0.071</td><td>0.354</td><td>0.125</td><td>0.765</td><td>-0.623</td><td>0.200</td><td>0.841</td></tr><tr><td>Cuttell et al., 2017 (10)</td><td>-0.170</td><td>0.356</td><td>0.127</td><td>0.528</td><td>-0.868</td><td>-0.476</td><td>0.634</td></tr><tr><td>Cuttell et al., 2017 (11)</td><td>0.000</td><td>0.354</td><td>0.125</td><td>0.693</td><td>-0.693</td><td>0.000</td><td>1.000</td></tr><tr><td>Cuttell et al., 2017 (12)</td><td>-0.170</td><td>0.356</td><td>0.127</td><td>0.528</td><td>-0.868</td><td>-0.476</td><td>0.634</td></tr><tr><td>Cuttell et al., 2017 (13)</td><td>-0.170</td><td>0.356</td><td>0.127</td><td>0.528</td><td>-0.868</td><td>-0.476</td><td>0.634</td></tr><tr><td>Cuttell et al., 2017 (14)</td><td>-0.176</td><td>0.356</td><td>0.127</td><td>0.522</td><td>-0.874</td><td>-0.494</td><td>0.621</td></tr><tr><td>Cuttell et al., 2017 (15)</td><td>-0.085</td><td>0.354</td><td>0.125</td><td>0.609</td><td>-0.779</td><td>-0.239</td><td>0.811</td></tr><tr><td>Cuttell et al., 2017 (16)</td><td>-0.082</td><td>0.354</td><td>0.125</td><td>0.612</td><td>-0.777</td><td>-0.233</td><td>0.816</td></tr><tr><td>Fonda et al., 2014 (1)</td><td>-0.419</td><td>0.301</td><td>0.091</td><td>0.171</td><td>-1.010</td><td>-1.393</td><td>0.164</td></tr><tr><td>Fonda et al., 2014 (2)</td><td>-0.441</td><td>0.302</td><td>0.091</td><td>0.152</td><td>-1.033</td><td>-1.458</td><td>0.145</td></tr><tr><td>Fonda et al., 2014 (3)</td><td>-0.878</td><td>0.340</td><td>0.115</td><td>-0.212</td><td>-1.544</td><td>-2.584</td><td>0.010</td></tr><tr><td>Fonda et al., 2014 (4)</td><td>-0.385</td><td>0.299</td><td>0.089</td><td>0.202</td><td>-0.971</td><td>-1.286</td><td>0.199</td></tr><tr><td>Fonda et al., 2014 (5)</td><td>-0.298</td><td>0.295</td><td>0.087</td><td>0.281</td><td>-0.876</td><td>-1.009</td><td>0.313</td></tr><tr><td>Fonda et al., 2014 (6)</td><td>-0.398</td><td>0.300</td><td>0.090</td><td>0.190</td><td>-0.985</td><td>-1.326</td><td>0.185</td></tr><tr><td>Fonda et al., 2014 (7)</td><td>-0.390</td><td>0.299</td><td>0.090</td><td>0.197</td><td>-0.976</td><td>-1.301</td><td>0.193</td></tr><tr><td>Fonda et al., 2014 (8)</td><td>-0.257</td><td>0.293</td><td>0.086</td><td>0.318</td><td>-0.832</td><td>-0.875</td><td>0.382</td></tr><tr><td>Fonda et al., 2014 (9)</td><td>-0.393</td><td>0.300</td><td>0.090</td><td>0.194</td><td>-0.980</td><td>-1.312</td><td>0.190</td></tr><tr><td>Fonda et al., 2014 (10)</td><td>-0.107</td><td>0.289</td><td>0.084</td><td>0.461</td><td>-0.674</td><td>-0.368</td><td>0.713</td></tr><tr><td>Fonda et al., 2014 (11)</td><td>0.063</td><td>0.289</td><td>0.083</td><td>0.629</td><td>-0.504</td><td>0.216</td><td>0.829</td></tr><tr><td>Fonda et al., 2014 (12)</td><td>-0.158</td><td>0.290</td><td>0.084</td><td>0.412</td><td>-0.727</td><td>-0.542</td><td>0.588</td></tr><tr><td>P.Zalewski et al., 2014 (1)</td><td>-0.731</td><td>0.225</td><td>0.051</td><td>-0.290</td><td>-1.172</td><td>-3.247</td><td>0.001</td></tr><tr><td>P.Zalewski et al., 2014 (2)</td><td>0.180</td><td>0.202</td><td>0.041</td><td>0.575</td><td>-0.215</td><td>0.892</td><td>0.373</td></tr><tr><td>P.Zalewski et al., 2014 (3)</td><td>0.188</td><td>0.202</td><td>0.041</td><td>0.583</td><td>-0.208</td><td>0.931</td><td>0.352</td></tr><tr><td>Zalewski et al., 2013 (1)</td><td>-0.727</td><td>0.205</td><td>0.042</td><td>-0.325</td><td>-1.129</td><td>-3.541</td><td>0.000</td></tr><tr><td>Zalewski et al., 2013 (2)</td><td>0.158</td><td>0.184</td><td>0.034</td><td>0.519</td><td>-0.202</td><td>0.863</td><td>0.388</td></tr><tr><td>Zalewski et al., 2013 (3)</td><td>0.131</td><td>0.183</td><td>0.034</td><td>0.490</td><td>-0.228</td><td>0.715</td><td>0.475</td></tr><tr><td>Lubkowska and Suska, 2011 (1)</td><td>-0.650</td><td>0.174</td><td>0.030</td><td>-0.309</td><td>-0.991</td><td>-3.733</td><td>0.000</td></tr><tr><td>Lubkowska and Suska, 2011 (2)</td><td>0.065</td><td>0.158</td><td>0.025</td><td>0.375</td><td>-0.245</td><td>0.410</td><td>0.682</td></tr><tr><td>Lubkowska and Suska, 2011 (3)</td><td>0.000</td><td>0.158</td><td>0.025</td><td>0.310</td><td>-0.310</td><td>0.000</td><td>1.000</td></tr><tr><td>Lubkowska and Susga, 2010 (1)</td><td>-0.650</td><td>0.220</td><td>0.048</td><td>-0.218</td><td>-1.081</td><td>-2.951</td><td>0.003</td></tr><tr><td>Lubkowska and Susga, 2010 (2)</td><td>0.064</td><td>0.200</td><td>0.040</td><td>0.456</td><td>-0.329</td><td>0.318</td><td>0.751</td></tr><tr><td>Lubkowska and Susga, 2010 (3)</td><td>-0.285</td><td>0.204</td><td>0.042</td><td>0.115</td><td>-0.685</td><td>-1.398</td><td>0.162</td></tr><tr><td>Lubkowska and Susga, 2010 (4)</td><td>-0.215</td><td>0.202</td><td>0.041</td><td>0.181</td><td>-0.612</td><td>-1.065</td><td>0.287</td></tr><tr><td>Louis et al., 2020 (1)</td><td>-0.734</td><td>0.356</td><td>0.127</td><td>-0.036</td><td>-1.432</td><td>-2.060</td><td>0.039</td></tr><tr><td>Louis et al., 2020 (2)</td><td>-0.674</td><td>0.350</td><td>0.123</td><td>0.013</td><td>-1.360</td><td>-1.923</td><td>0.054</td></tr><tr><td>Louis et al., 2020 (3)</td><td>-0.924</td><td>0.378</td><td>0.143</td><td>-0.184</td><td>-1.665</td><td>-2.447</td><td>0.014</td></tr><tr><td>Louis et al., 2020 (4)</td><td>-1.272</td><td>0.425</td><td>0.181</td><td>-0.438</td><td>-2.105</td><td>-2.990</td><td>0.003</td></tr><tr><td>Coppi et al., 2022</td><td>1.346</td><td>0.437</td><td>0.191</td><td>2.201</td><td>0.490</td><td>3.083</td><td>0.002</td></tr><tr><td>Rose et al., 2023 (1)</td><td>-0.394</td><td>0.367</td><td>0.135</td><td>0.326</td><td>-1.113</td><td>-1.073</td><td>0.283</td></tr><tr><td>Rose et al., 2023 (2)</td><td>-0.948</td><td>0.401</td><td>0.161</td><td>-0.162</td><td>-1.735</td><td>-2.363</td><td>0.018</td></tr><tr><td>Miller et al., 2012 (1)</td><td>0.182</td><td>0.336</td><td>0.113</td><td>0.840</td><td>-0.477</td><td>0.540</td><td>0.589</td></tr><tr><td>Miller et al., 2012 (2)</td><td>-0.400</td><td>0.346</td><td>0.120</td><td>0.279</td><td>-1.079</td><td>-1.156</td><td>0.248</td></tr><tr><td>Miller et al., 2012 (3)</td><td>0.033</td><td>0.333</td><td>0.111</td><td>0.686</td><td>-0.621</td><td>0.098</td><td>0.922</td></tr><tr><td>Miller et al., 2012 (4)</td><td>0.037</td><td>0.333</td><td>0.111</td><td>0.691</td><td>-0.616</td><td>0.112</td><td>0.911</td></tr><tr><td>Miller et al., 2012 (5)</td><td>-0.169</td><td>0.336</td><td>0.113</td><td>0.489</td><td>-0.826</td><td>-0.502</td><td>0.616</td></tr><tr><td>Miller et al., 2012 (6)</td><td>-0.115</td><td>0.334</td><td>0.112</td><td>0.540</td><td>-0.771</td><td>-0.344</td><td>0.731</td></tr><tr><td>Srerek et al., 2000 (1)</td><td>1.310</td><td>0.431</td><td>0.186</td><td>2.155</td><td>0.465</td><td>3.039</td><td>0.002</td></tr><tr><td>Srerek et al., 2000 (2)</td><td>-0.603</td><td>0.344</td><td>0.118</td><td>0.071</td><td>-1.276</td><td>-1.753</td><td>0.080</td></tr><tr><td>Srerek et al., 2000 (3)</td><td>-2.405</td><td>0.624</td><td>0.389</td><td>-1.182</td><td>-3.628</td><td>-3.855</td><td>0.000</td></tr><tr><td>Srerek et al., 2000 (4)</td><td>-3.149</td><td>0.772</td><td>0.596</td><td>-1.636</td><td>-4.662</td><td>-4.080</td><td>0.000</td></tr><tr><td>Srerek et al., 2000 (5)</td><td>-3.272</td><td>0.797</td><td>0.635</td><td>-1.710</td><td>-4.835</td><td>-4.105</td><td>0.000</td></tr><tr><td>Srerek et al., 2000 (6)</td><td>-3.215</td><td>0.785</td><td>0.617</td><td>-1.676</td><td>-4.755</td><td>-4.094</td><td>0.000</td></tr><tr><td>Einmont et al., 2021 (1)</td><td>1.661</td><td>0.445</td><td>0.198</td><td>2.534</td><td>0.788</td><td>3.730</td><td>0.000</td></tr><tr><td>Einmont et al., 2021 (2)</td><td>1.672</td><td>0.447</td><td>0.200</td><td>2.548</td><td>0.796</td><td>3.740</td><td>0.000</td></tr><tr><td>Einmont et al., 2021 (3)</td><td>1.133</td><td>0.370</td><td>0.137</td><td>1.858</td><td>0.408</td><td>3.063</td><td>0.002</td></tr><tr><td>Einmont et al., 2021 (4)</td><td>0.304</td><td>0.295</td><td>0.087</td><td>0.883</td><td>-0.274</td><td>1.031</td><td>0.303</td></tr><tr><td>Einmont et al., 2021 (5)</td><td>0.178</td><td>0.291</td><td>0.085</td><td>0.749</td><td>-0.392</td><td>0.613</td><td>0.540</td></tr><tr><td>Einmont et al., 2021 (6)</td><td>0.157</td><td>0.290</td><td>0.084</td><td>0.727</td><td>-0.412</td><td>0.542</td><td>0.588</td></tr><tr><td>Einmont et al., 2021 (7)</td><td>0.041</td><td>0.289</td><td>0.083</td><td>0.608</td><td>-0.525</td><td>0.144</td><td>0.886</td></tr><tr><td>Einmont et al., 2021 (8)</td><td>0.087</td><td>0.289</td><td>0.084</td><td>0.653</td><td>-0.480</td><td>0.299</td><td>0.765</td></tr><tr><td>Einmont et al., 2021 (9)</td><td>0.067</td><td>0.289</td><td>0.084</td><td>0.633</td><td>-0.500</td><td>0.230</td><td>0.818</td></tr><tr><td>Einmont et al., 2021 (10)</td><td>0.086</td><td>0.289</td><td>0.084</td><td>0.653</td><td>-0.480</td><td>0.299</td><td>0.765</td></tr><tr><td>Einmont et al., 2021 (11)</td><td>0.000</td><td>0.289</td><td>0.083</td><td>0.566</td><td>-0.566</td><td>0.000</td><td>1.000</td></tr><tr><td>Einmont et al., 2021 (12)</td><td>-0.067</td><td>0.289</td><td>0.084</td><td>0.500</td><td>-0.633</td><td>-0.231</td><td>0.817</td></tr><tr><td>Einmont et al., 2021 (13)</td><td>0.220</td><td>0.292</td><td>0.085</td><td>0.793</td><td>-0.352</td><td>0.754</td><td>0.451</td></tr><tr><td>Vogelacre et al., 1995</td><td>0.814</td><td>0.516</td><td>0.266</td><td>1.826</td><td>-0.197</td><td>1.578</td><td>0.115</td></tr><tr><td>Jansky et al., 1996 (1)</td><td>-0.043</td><td>0.316</td><td>0.100</td><td>0.577</td><td>-0.663</td><td>-0.136</td><td>0.892</td></tr><tr><td>Jansky et al., 1996 (2)</td><td>0.907</td><td>0.376</td><td>0.141</td><td>1.644</td><td>0.171</td><td>2.415</td><td>0.016</td></tr><tr><td>Kwicien et al., 2019 (1)</td><td>-0.792</td><td>0.346</td><td>0.119</td><td>-0.115</td><td>-1.469</td><td>-2.292</td><td>0.022</td></tr><tr><td>Mintoni et al., 2007</td><td>1.931</td><td>0.469</td><td>0.220</td><td>2.851</td><td>1.011</td><td>4.114</td><td>0.000</td></tr><tr><td>Barwod et al., 2014</td><td>-0.808</td><td>0.332</td><td>0.111</td><td>-0.156</td><td>-1.459</td><td>-2.430</td><td>0.015</td></tr><tr><td>Mintoni et al., 2008</td><td>1.369</td><td>0.464</td><td>0.215</td><td>2.278</td><td>0.459</td><td>2.951</td><td>0.003</td></tr><tr><td>Brazaitis et al., 2014</td><td>6.562</td><td>1.269</td><td>1.609</td><td>9.049</td><td>4.076</td><td>5.173</td><td>0.000</td></tr><tr><td></td><td>-0.157</td><td>0.061</td><td>0.004</td><td>-0.036</td><td>-0.277</td><td>-2.549</td><td>0.011</td></tr></tbody></table>

<figure><img src="image_14.png" /><figcaption>Forest plots of the effect of cold exposure on heart rate</figcaption></figure>
<figure><img src="image_14.png" /></figure>