# Effects of home-based slow-paced breathing on functional performance in middle-aged women: A randomized controlled trial study

Karama Masmoudi, Fatma Chaari, Haithem Rebai, Sonia Sahli

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Karama Masmoudi, Fatma Chaari, Haithem Rebai, Sonia Sahli. Effects of home-based slow-paced breathing on functional performance in middle-aged women: A randomized controlled trial study. Experimental Gerontology, 2025, 209, pp.112854. 10.1016/j.exger.2025.112854. hal-05459090

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# Effects of home-based slow-paced breathing on functional performance in middle-aged women: A randomized controlled trial study

Karama Masmoudi<sup>a,b</sup>, Fatma Chaari<sup>a,c,*</sup>, Haithem Rebai<sup>a</sup>, Sonia Sahli<sup>a</sup>

<figure><img src="image_3.png" /></figure>

## ARTICLE INFO

Section Editor: Christiaan Leeuwenburgh

**Keywords:**

- Post-menopause

- Diaphragmatic breathing

- Breathing exercise

- Postural control

- Physical functions

- Females

- Post-menopausal

## ABSTRACT

As individuals age, functional performance declines, particularly affecting mobility, strength, and postural balance, with middle-aged women experiencing earlier and more pronounced impairments due to menopausal transition. Given the low adherence to traditional exercise programs among this population, home-based slow-paced breathing (SPB) presents a promising accessible alternative. Hence, this study aimed to examine the effects of a 12-week daily SPB intervention on functional performance in middle-aged women.

Twenty-six middle-aged women were randomized into an experimental group (EG), which practiced home-based SPB, or a control group (CG), which continued their usual activities. Static postural balance, upper- and lower-limb muscle strength, mobility and dynamic balance, and aerobic endurance were evaluated at pre-intervention, post-4, post-8, and post-12 weeks of intervention.

Static postural balance improved on a firm surface within the EG post-12 weeks of intervention, though no significant differences emerged between groups. On a foam surface, improvements emerged post-8 weeks in the eyes-open condition and post-4 weeks in the eyes-closed condition. Additionally, aerobic endurance improved within the EG post-8 weeks, with no significant differences between groups. No significant group x session interactions were found for other functional performances.

These findings indicate that middle-aged women who practiced or not the SPB demonstrated similar functional outcomes, suggesting that SPB alone may not be sufficient to induce significant improvements in functional performances. Exploring the effects of integrating SPB with muscle-strengthening exercises or neuromuscular training could be interesting to determine whether a combined approach could yield greater functional benefits and address the limitations of the observed non-significant results.

## 1. Introduction

As individuals age, functional performance progressively declines, particularly impairing mobility, strength, and postural balance (Okabe et al., 2021). The onset of these impairments starts during middle age, with women experiencing a more pronounced decline, not only due to aging but also as a result of hormonal shifts associated with the menopause transition (Cheng et al., 2009; Isles et al., 2004; Mechakra-Tahiri et al., 2012; Zunzunegui et al., 2015). Such impairments are associated with frailty, hospitalization, and an increased risk of mortality (Cooper et al., 2010; Eekhoff et al., 2019; Guadalupe-Grau et al., 2015). Hence, slowing or preventing the progression of these impairments is a key

focus in the care of aging populations. However, a common challenge among middle-aged women is their limited adherence to traditional exercise programs, often citing time constraints as a primary barrier (Joseph et al., 2015). Therefore, there is a need for a program that can be easily implemented into their daily routines, such as home-based slow-paced breathing (SPB).

Interestingly, SPB has been suggested as an advantageous technique compared to other approaches as they need no equipment or specific setting and can be easily learned and self-administered, which makes them cost-effective (Hopper et al., 2019). The term “paced” means that participants have to regulate the duration of inhalation and exhalation phases following a visual, auditory, or kinesthetics pacer regulating

<footnote><sup>a</sup> Tunisian Research Laboratory 'Sports Performance Optimization (LR09SEP01), National Center of Medicine and Science in Sports (CNMSS), Tunis, Tunisia</footnote>

<footnote><sup>b</sup> Higher Institute of Sport and Physical Education of Sfax, University of Sfax, Airport road km 3.5, BP 384, 3000 Sfax, Tunisia</footnote>

<footnote><sup>c</sup> Le Mans University, Movement - Interactions, Performance, MIP, UR4334, France Faculty of Sciences and Technologies, Avenue Olivier Messiaen, 72000 Le Mans, France</footnote>

<footnote>* Corresponding author at: Le Mans University, Movement - Interactions, Performance, MIP, UR4334, France Faculty of Sciences and Technologies, Avenue Olivier Messiaen, 72000 Le Mans, France.</footnote>

<footnote>E-mail address: chaarifatma94@gmail.com (F. Chaari).</footnote>
making the exhalation last slightly longer than inhalation (You et al., 2021). It is widely recognized for its numerous benefits of various dimensions of functional performances, such as postural balance (Han et al., 2019) and cardiovascular fitness and endurance (Migliaccio et al., 2023) among athletes. These benefits are evident even with home-based SPB. In chronic heart failure patients, 4 weeks of home-based SPB enhanced pulmonary gas exchange and performance in the 6-min walking test by increasing oxygen saturation, peak oxygen consumption, and exercise time while reducing dyspnea (Bernardi et al., 1998). Similarly, in chronic obstructive pulmonary disease patients, home-based SPB improved respiratory muscle strength and aerobic endurance after 8 weeks (Gu et al., 2018). Additionally, a recent study reported static postural balance improvements in middle-aged women (on a firm surface with eyes closed (EC) and on a foam surface irrespective of vision condition) following a single SPB session (Masmoudi et al., 2025). However, these improvements were non-significant compared to their counterparts who did not practice SPB. It could be hypothesized that one session of SPB is not sufficient to improve postural balance outcomes in these women, and longer time of SPB practice would be necessary. While improvements have been reported following 4- or 8-week programs in clinical populations, it remains unclear whether such durations are sufficient to elicit measurable changes in relatively healthy, middle-aged women.

Given the beneficial effects of long-term SPB training on functional performances in different populations, we aimed to explore the effects of SPB in middle-aged women to assess if longer periods could produce more significant results on functional performances in these women. Such a study could offer insights into alternative approaches that are relatively cheap and time-efficient to promote these women's functional performances. Thus, the aim of this study was to examine the effect of a 12-week home-based daily SPB on functional performance in middle-aged women. We hypothesized that the 12 weeks of home-based SPB would improve these women's functional performances.

## 2. Methods

### 2.1. Participants and study design

This study is a randomized controlled trial with a single-blind design. It was conducted in accordance with the Declaration of Helsinki and approved by the local Ethics Committee from the High Institute of Nursing, University of Sfax, Tunisia (Protection Committee approval number CPP: 0408/2022). It is part of a larger clinical study registered in accordance with WHO and ICMJE standards on the Pan African Clinical Trial Registry. The present manuscript presents a subset of the data focused on functional performance outcomes in middle-aged postmenopausal women. The broader study also examines additional outcomes such as cognitive performance and heart rate variability, which will be reported separately.

As no previous study had assessed the same intervention in middle-aged women over several weeks, an a priori sample size estimate was calculated based on a previous study by Masmoudi et al. (2025), that examined the immediate effects of SPB on postural balance. The calculations were performed using G*Power software (version 3.1.9.7; Kiel, Germany) using an effect size of 0.25, α error probability of 0.05, power (1-β) of 0.80, 2 groups, and 4 measurements (pre-, post-4, post-8, and post-12 weeks of intervention), to monitor the evolution of intervention effects on the functional outcomes. It reported a total sample size equal to 24. To account for potential dropouts, we recruited 36 participants through direct advertising and social media campaigns.

Participants were invited to the research laboratory for eligibility screening. Inclusion criteria were being healthy, aged between 50 and 60 years old, postmenopausal for at least 5 years, with a score of 25 or higher on the Arabic Mini-Mental State Examination and a normal respiratory rate of 12-20 cycles per minute. Exclusion criteria included smoking, undergoing hormone replacement therapy, engaging in

breathing-exercise programs within one month prior to the study, taking vestibular sedatives, other central nervous system depressants, or any medications or having any chronic or severe medical conditions, neuropsychiatric disorders, or impairments potentially affecting postural balance, breathing, or cardiorespiratory function. All participants provided written informed consent before participating in the study. The privacy rights of the participants were strictly adhered to, and all personal data was kept confidential throughout the research process.

### 2.2. Intervention

A total of 36 women were initially screened for eligibility. Of these, 4 did not meet the inclusion criteria and 2 declined to participate, resulting in 30 women who were enrolled and randomly distributed equally by a web-based survey randomizer into either an experimental group (EG) or a control group (CG). During the study, 4 participants were lost to follow-up, leaving a final sample of 26 participants (Fig. 1). A familiarization session was conducted one week prior to baseline assessments in a research laboratory by a certified physiotherapist. Participants were instructed to breathe at a frequency of 6 breaths per minute, using a 4-s nasal inhalation and a 6-s exhalation through pursed lips, emphasizing diaphragmatic movement throughout (Laborde et al., 2022). Then, they were given a 15-min video with an auditory and visual pacer to practice daily at home for 12 weeks. During the intervention period, participants of the EG received daily text messages prompting them to report whether or not they had completed the breathing exercise via an online form. On the other hand, participants in the CG were not subjected to any exercise program and were required to carry on doing their habitual activities. Similarly, they received daily check-in messages to maintain engagement and monitor any issues or changes in health status. Interactions with the CG were brief and non-directive and were implemented to help balance attention across groups without introducing active components of the intervention.

### 2.3. Outcome measures

The study took place between May and August 2024. Participants underwent measurements in 4 sessions: pre-intervention, post-4, post-8, and post-12 weeks of intervention. Testing sessions were consistently scheduled in the morning to minimize circadian variation in physiological responses (Lahiani et al., 2023). All assessments were carried out by a single examiner who remained blind to participants' groups throughout the testing process. Additionally, participants were required not to disclose that information to the examiner or other participants. Moreover, participants in the EG were instructed not to practice SPB during the functional tests to avoid acute effects influencing performance outcomes.

Static postural balance was evaluated using a static stabilometric platform (Techno Concept®, Manosque, France). Data was collected under 2 visual conditions. In the eyes open condition (EO), females were instructed to keep their gaze horizontally on a visual target positioned 2 m away. In the EC, they were required to wear a blindfold to eliminate visual input. Each visual condition was tested on both firm and foam surfaces to challenge different sensory contributions. Three trials were performed for each experimental condition, and the results were averaged per condition and participant to obtain a representative measure of postural balance. The center of pressure mean velocity (CoP<sub>Vm</sub>) was chosen, as it best reflects the most accurate form of sensory information used to stabilize posture during the quiet stance (Jeka et al., 2004). CoP<sub>Vm</sub> is calculated by dividing the total CoP displacement by the duration of the trial and can be analyzed along mediolateral and anteroposterior axes or as a resultant vector. It reflects the efficiency of the postural control system as lower CoP<sub>Vm</sub> values indicate better balance and more effective neuromuscular regulation to maintain stability (Paillard and Noë, 2006).

The upper limb muscle strength was measured using the Arm Curl
<figure><img src="image_4.png" /><figcaption>Fig. 1. Flowchart of participants' enrolment.</figcaption></figure>

test, which has been widely used among middle-aged women in scientific research (Waer et al., 2021; Pullyblank et al., 2020). This test quantifies the number of repetitions to perform a biceps-curl as fast as possible by participants while holding a hand weight of 2.27 kg for 30 s. The number of repetitions was used for analysis (Rikli and Jones, 2013).

Lower limb muscle strength was assessed using the 30-s Chair Stand test, which has demonstrated excellent test-retest reliability (Assis Silva et al., 2024). The participants began the test seated upright in a chair that did not have armrests, with their arms folded across their chest. They were required to stand up from the chair and sit back as many times as possible for 30 s. The number of repetitions was used for analysis (Rikli and Jones, 2013).

The mobility and dynamic balance were assessed using the timed up-and-go (TUG) test, which has demonstrated excellent test-retest reliability (Assis Silva et al., 2024). Participants started the test seated in a chair without armrests. Upon receiving the start signal, they were instructed to stand, walk to a point 3 m away, return as quickly as possible, and then sit back down. The time taken to complete the task was recorded for analysis, with longer times indicating poorer performance (Rikli and Jones, 2013). Participants conducted two trials, with the best score recorded for analysis (Rikli and Jones, 1999).

The aerobic endurance was measured using the 2-Minute Step, which has been widely used among middle-aged women in scientific research (Waer et al., 2021; Pullyblank et al., 2020). During the test, participants were required to lift their knees in a marching-like motion during a 2-min period, to a point midway between the patella and the iliac crest. The number of repetitions was used for analysis (Rikli and Jones, 2013).

## 2.4. Statistical analysis

Statistical tests were processed using IBM SPSS® Statistics version 26, 64 bits (IBM Corp, Armonk, NY, USA). The values were expressed as

mean ± standard deviation (M ± SD).

Since data normality distribution, homogeneity of variances, and sphericity were confirmed using the Shapiro-Wilk W test, Levene's, and the Mauchly test, respectively, parametric tests were applied. A three-way repeated measures ANOVA [2 groups × 4 sessions × 2 visions] in both surface conditions (firm and foam) was used to determine the effects of the group (CG/EG), session (pre-/post-4 weeks/ post-8 weeks/ post-12 weeks) and vision (EO/EC) factors on the CoP<sub>Vm</sub> values. The data for the other functional tests were analyzed using a two-way ANOVA [2 groups (CG/EG) x 4 sessions (pre-/post-4 weeks/ post-8 weeks/ post-12 weeks)]. When significant interaction was observed (p < 0.05), a post-hoc analysis was then performed with the Bonferroni test. The effect sizes are indicated using partial eta squared (small effect: 0.01 < η<sup>2</sup><sub>p</sub> < 0.06; medium effect: 0.06 < η<sup>2</sup><sub>p</sub> < 0.14; large effect: η<sup>2</sup><sub>p</sub> > 0.14).

## 3. Results

The study was conducted between May and August 2024, with 30 participants initially recruited (Fig. 1). Of these, 26 completed the full 12-week intervention. Four participants, 2 from each group, did not complete the study and were excluded from all analyses. No harm or

<table><caption>**Table 1**
Mean ± SD of participants' characteristics.</caption><thead><tr><th></th><th>EG (n = 13)</th><th>CG (n = 13)</th><th>p</th></tr></thead><tbody><tr><td>Age (years)</td><td>55.08 ± 2.06</td><td>54.08 ± 2.81</td><td>0.16</td></tr><tr><td>Height (m)</td><td>1.58 ± 0.04</td><td>1.60 ± 0.04</td><td>0.65</td></tr><tr><td>Weight (kg)</td><td>64.92 ± 3.43</td><td>67.69 ± 5.53</td><td>0.99</td></tr><tr><td>Body mass index (kg/m<sup>2</sup>)</td><td>26.86 ± 2.67</td><td>26.23 ± 2.43</td><td>0.58</td></tr><tr><td>Breathing frequency (breaths/min)</td><td>16.23 ± 1.59</td><td>16.46 ± 1.27</td><td>0.46</td></tr></tbody></table>

Notes: CG: Control group, EG: Experimental group.
adverse events occurred in either group throughout the study period. Table 1 presents the group characteristics, revealing no significant differences between them at baseline. Regarding adherence, participants in the EG attended an average of 96.43 % ± 2.46 %.

Regarding static postural balance, on the firm surface, the three-way ANOVA showed significant main effects of the session and vision factors, as well as the group x session interaction on the CoPV<sub>m</sub> values. However, no significant effect of group factor, vision x session, group x vision, and group x session x vision interactions were found on the CoPV<sub>m</sub> values (Table 2). Concerning the session effect, the post-hoc analysis showed that, irrespective of the vision condition, the EG demonstrated significantly lower CoPV<sub>m</sub> values post-12 weeks of intervention in comparison to pre-intervention. Additionally, in the EC, this group demonstrated significantly lower CoPV<sub>m</sub> values post-12 weeks in comparison to post-4 weeks of intervention. However, in both vision conditions, the CG demonstrated no significant differences between the different sessions. Concerning the group effect, no significant differences were found between groups in any session or under any vision condition (Fig. 2).

On the foam surface, the three-way ANOVA showed significant main effects of the session and vision factors and significant main effects of group x session and group x vision interactions on the CoPV<sub>m</sub> values. However, no significant main effect of group factor, vision x session, and group x vision x session interactions were observed (Table 2). Concerning the vision effect, both groups demonstrated values of CoPV<sub>m</sub> significantly higher in the EC compared to the EO condition in all sessions. Concerning the group effect, the EG showed significantly lower CoPV<sub>m</sub> values compared to the CG in EC condition at pre-intervention, post-4, and post-8 weeks of intervention. Concerning the session effect, in the EO condition, the EG demonstrated significantly lower values of CoPV<sub>m</sub> post-8 and post-12 weeks of intervention in comparison to pre-intervention and post-4 weeks of intervention. In the EC condition, the same group demonstrated significantly lower values of CoPV<sub>m</sub> post-12, post-8, and post-4 weeks compared to pre-intervention. Besides, CoPV<sub>m</sub> values were significantly lower post-12 weeks compared to post-4 and post-8 weeks of intervention. However, in the CG, there was no significant difference between the different sessions, irrespective of vision conditions (Fig. 3).

Regarding upper limb strength, the two-way ANOVA revealed a significant main effect of the session (F = 12.52, *p* ≤ 0.001, η<sup>2</sup><sub>p</sub> = 0.34). However, no significant effect was found for the group (F = 0.22, *p* = 0.65, η<sup>2</sup><sub>p</sub> = 0.01) or the group x session interaction (F = 0.39, *p* = 0.68, η<sup>2</sup><sub>p</sub> = 0.02).

Regarding lower limb strength, the two-way ANOVA revealed a significant main effect of the session (F = 6.60, *p* ≤ 0.001, η<sup>2</sup><sub>p</sub> = 0.22). However, no significant effect was found for the group (F = 0.89, *p* = 0.60, η<sup>2</sup><sub>p</sub> = 0.01) or the group x session interaction (F = 0.54, *p* = 0.65, η<sup>2</sup><sub>p</sub> = 0.02).

Regarding mobility and dynamic balance, the two-way ANOVA revealed a significant main effect of the session (F = 22.93, *p* ≤ 0.001, η<sup>2</sup><sub>p</sub> = 0.49) and the group (F = 6.72, *p* ≤ 0.05, η<sup>2</sup><sub>p</sub> = 0.22). However, no significant effect was found for the group x session interaction (F = 1.36, *p* = 0.26, η<sup>2</sup><sub>p</sub> = 0.05).

<caption>**Table 2**</caption>

Summary of the ANOVA results of the mean center of pressure velocity on the firm and foam surface conditions with eyes opened and eyes closed.

<table><thead><tr><th rowspan="2"></th><th colspan="3">Firm surface</th><th colspan="3">Foam surface</th></tr><tr><th>F</th><th>p</th><th>η<sup>2</sup><sub>p</sub></th><th>F</th><th>p</th><th>η<sup>2</sup><sub>p</sub></th></tr></thead><tbody><tr><td>Group</td><td>0.18</td><td>0.68</td><td>0.01</td><td>3.25</td><td>0.08</td><td>0.12</td></tr><tr><td>Session</td><td>8.24</td><td>&lt;0.001</td><td>0.26</td><td>17.29</td><td>&lt;0.001</td><td>0.42</td></tr><tr><td>Vision</td><td>80.33</td><td>&lt;0.001</td><td>0.77</td><td>65.26</td><td>&lt;0.001</td><td>0.73</td></tr><tr><td>Vision x session</td><td>0.49</td><td>0.69</td><td>0.02</td><td>2.62</td><td>0.06</td><td>0.10</td></tr><tr><td>Group x Session</td><td>2.73</td><td>&le;0.05</td><td>0.10</td><td>6.31</td><td>&lt;0.001</td><td>0.21</td></tr><tr><td>Group x Vision</td><td>0.89</td><td>0.36</td><td>0.04</td><td>5.08</td><td>&le;0.05</td><td>0.18</td></tr><tr><td>Group x Session x Vision</td><td>0.40</td><td>0.77</td><td>0.02</td><td>2.49</td><td>0.07</td><td>0.94</td></tr></tbody></table>

Regarding aerobic endurance, the two-way ANOVA revealed a significant main effect of the session (F = 15.66, *p* ≤ 0.001, η<sup>2</sup><sub>p</sub> = 0.40) and of the group x session interaction (F = 3.34, *p* ≤ 0.05, η<sup>2</sup><sub>p</sub> = 0.12) on 2-min step test. However, no significant effect was found for the group (F = 0.16, *p* = 0.70, η<sup>2</sup><sub>p</sub> = 0.01). The post-hoc analysis showed a significant increase in the number of steps between the pre-intervention values and those collected post-8 and post-12 weeks in the EG. Besides, these values increased significantly post-8 and post-12 weeks of intervention compared to post-4 weeks in this group (Fig. 4).

## 4. Discussion

The aim of the present study was to investigate the effects of a 12-week home-based SPB on functional performances in middle-aged women. The main findings indicated an improvement in static postural balance, on the firm surface, within the EG, after 12 weeks of home-based SPB, with no significant differences between groups, irrespective of vision condition. On the foam surface, improvements were observed starting from 8 weeks of intervention in the EO condition and from 4 weeks of intervention in the EC condition. Surprisingly, the EG had significantly higher CoP values at pre-, post-4 and post-8 weeks of intervention, which disappeared post-12 weeks of intervention compared to CG. Besides, aerobic endurance improved within the EG post-8 weeks of intervention, with no significant differences between groups. However, our results showed no significant group x session interactions on other functional performances (upper- and lower-limb muscle strength and mobility and dynamic balance).

Our findings suggest that participants who did or did not practice home-based SPB for 12 weeks showed similar functional performances. To the best of our knowledge, this is the first study to investigate the effects of a 12-week home-based SPB intervention on functional performance in middle-aged women, making direct comparisons with previous studies inapplicable. In terms of static postural balance, the EG exhibited improvements in both visual conditions after 12 weeks on the firm surface. On the foam surface, they exhibited improvements starting as early as 8 weeks in the EO condition and 4 weeks in the EC condition. However, no significant differences were found between groups on the firm surface. It seems that improvements were observed in the EG during challenging conditions and not in the easy ones. Previous studies that have explored the immediate effects of SPB on static postural balance reported improvements within the EG also in difficult conditions such as standing on a foam surface or single-leg standing. Indeed, findings showed significant immediate improvements in middle-aged women practicing the SPB in the static postural balance, on the firm surface, in the EC condition, and on the foam surface, irrespective of the vision conditions, with no significant differences between groups (Masmoudi et al., 2025). Furthermore, in young athletes, incorporating SPB in a physical exercise session led to significant improvements in static postural balance, particularly during single-leg standing on the non-dominant side, with no significant effects observed in bilateral standing following a single session, compared to a group that only practiced physical exercises (Han et al., 2019). The improvements observed in challenging conditions (i.e. standing on a foam surface) could be explained by the fact that these conditions require greater reliance on both the visual and vestibular systems to maintain postural balance, as these sensory inputs play a crucial role in compensating for the reduced proprioceptive feedback from the unstable surface (Fujimoto et al., 2009). SPB was found to modulate the autonomic nervous system through vagus nerve stimulation (Zaccaro et al., 2018), optimizing the control of both the visual (Ad and Raju, 2023) and vestibular systems (Eren et al., 2018). These two systems are essential for maintaining postural balance, with the visual system providing spatial orientation cues and the vestibular system detecting head movements to support posture adjustments (Beraneck et al., 2014; Kennedy et al., 2013). Given the ability of SPB to influence autonomic function, one could hypothesize that improvements in postural balance in the EG following SPB is
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Data concerning CoPvm on the firm surface with EO and EC in the pre-, post-4, post-8, and post-12 weeks of intervention for EG and CG
Notes: CG: control group, CoPVm: center of pressure mean velocity, EC: eyes closed, EG: experimental group, EO: eyes open.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Data concerning CoPvm on the foam surface with EO and EC in the pre-, post-4, post-8, and post-12 weeks of intervention for EG and CG
Notes: CG: control group, CoPVm: center of pressure mean velocity, EC: eyes closed, EG: experimental group, EO: eyes open</figcaption></figure>

obvious under more challenging conditions that demand heightened
sensory integration. Moreover, when task difficulty increases, postural
balance is further challenged (Visser et al., 2008), and worse balance
performance could be observed, and this potentially allows for more
room for improvement.

Additionally, our results showed significant differences between

groups at pre-intervention concerning static postural balance in the EC
condition on the foam surface, which disappeared by the 12th week of
the intervention. The differences could be due to a potentially under-
diagnosed pre-existing health condition. Indeed, standing on a foam
surface with EC perturbates visual and proprioceptive inputs, obligating
participants to rely more on vestibular information (Koo et al., 2015).

<footnote>*: significantly different at: \*p ≤ 0.05, \*\*p < 0.01.</footnote>

<footnote>$: significantly different at: $p ≤ 0.05, \$$p < 0.01, \$$\$p < 0.001</footnote>

<footnote>*: significantly different at: \*p ≤ 0.05, \*\*p < 0.01, \*\*\*p < 0.001</footnote>

<footnote>+: significantly different at: +p ≤ 0.05, ++p < 0.01.</footnote>
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Data concerning the aerobic endurance in the pre-, post-4, post-8, and post-12 weeks of intervention for EG and CG
*Notes:* CG: control group, EG: experimental group
\*: significantly different at: \*\* p < 0.01, \*\*\* p < 0.001.</figcaption></figure>

However, vestibular disorders are usually underdiagnosed and can go unnoticed by health clinicians (Comolli et al., 2023). Furthermore, women are more marginalized when it comes to diseases and health complaints and, most of the time, are underdiagnosed (Merone et al., 2022). This could hypothetically explain the unexpected differences found at pre-intervention between groups.

Regarding aerobic endurance, the EG exhibited improvements after 8 weeks of SPB. However, these improvements were not significant compared to CG. To the best of our knowledge, no previous study assessed the effects of SPB on aerobic endurance among middle-aged women, therefore, it would not be possible to make direct comparisons. However, previous studies have assessed the effects of different breathing exercises on aerobic endurance in patients with chronic obstructive pulmonary disease and found different results. For instance, Yekefallah et al. (2019) reported significant improvements within patients who practiced another modality of breathing techniques (deep diaphragmatic breathing) four times daily for one month. However, when compared to the CG, these differences were not statistically significant (Yekefallah et al., 2019). Meanwhile, Yamaguti et al. (2012) assessed the effects of SPB practiced in different positions (to increase resistance on breathing muscles) during three 45-min sessions per week for four weeks on aerobic endurance, and reported significant improvement, as assessed by the 6-min walking distance, compared to the CG. The inconsistent findings could be attributed to the higher intensity and specific positioning of the intervention protocol used in this study. Another possible explanation is the difference in assessment methods, as the tests used to evaluate aerobic capacity may vary in their sensitivity to changes between populations.

SPB has been shown to enhance aerobic endurance by slowing the breathing rate and increasing tidal volume (Bernardi et al., 2001; Russo et al., 2017). This combination helps improve ventilatory efficiency, as it reduces the amount of unused lung space, leading to better oxygen saturation and, as a result, improved aerobic performance (Bilo et al., 2012). However, it is possible that our SPB program was insufficient to induce significant improvements in aerobic endurance compared to the CG due to several factors, such as the insufficient frequency or intensity of the program. Another explanation could have been variations in participant adherence to home-based practice (Argent et al., 2018). Although adherence was assessed via an online questionnaire, participants may have misreported their actual practice, leading to potential overestimation of compliance.

Regarding the rest of the functional performances, no significant group x session interactions were reported. This suggests that 12 weeks of home-based SPB does not significantly improve upper- and lower-limb muscle strength or mobility and dynamic balance in middle-aged women. In another population, 12 weeks of a different modality of breathing exercises (Yogic breathing) was assessed, and findings showed no significant effects on handgrip strength in healthy young adults (Thangavel et al., 2014). Concerning the upper- and lower-limb muscle strength, research indicates that SPB does not directly improve muscle strength, however, it can improve recovery and physiological responses, which might indirectly enhance muscle strength (Buxton et al., 2024). In fact, SPB reduces sympathetic nervous system activity (Buxton et al., 2024), leading to enhanced recovery by improving blood flow and oxygen delivery to muscles (Vianna et al., 2016). This, in turn, delays fatigue and improves performance in exercises requiring repetitive movements (Buxton et al., 2024). However, our program of 12 weeks of home-based SPB did not lead to improvements in upper- and lower-limb muscle strength. The lack of significant improvements could be attributed to several factors. While SPB is beneficial for recovery and autonomic regulation (Buxton et al., 2024), it does not directly stimulate muscle tissue or the neuromuscular function necessary for neuromuscular performances (Faude et al., 2017), muscle hypertrophy or strength gains (Mangine et al., 2015; Ni et al., 2012). Thus, its effect on upper- and lower-limb muscle strength remains limited.

Concerning mobility and dynamic balance, SPB has been proposed as a technique that could optimize diaphragmatic function (Nelson, 2012). The diaphragm, working in coordination with the abdominal muscles, helps stabilize the spine by generating intra-abdominal pressure, which acts as a supportive mechanism for the lumbar region (Faulkner, 1986; Kolar et al., 2009; Miyamoto et al., 2002). Indeed, SPB requires a controlled engagement of the abdominal muscles to actively increase intra-abdominal pressure, which in turn elevates the diaphragm (Kim and Lee, 2013). This process is believed to improve core stability and reinforce postural balance, potentially leading to better balance and mobility (Nelson, 2012). However, despite these potential mechanisms, no significant session*group interaction were observed in mobility and dynamic balance in the current study. The lack of significant results could be also explained with the same mechanism reported for the muscle strength.

The findings of this study suggest that 12 weeks of home-based SPB led to improvements in static postural balance and aerobic endurance
within the EG. However, these within-group improvements, although encouraging, may reflect non-specific effects or insufficient intervention intensity to generate distinct between-group differences. Furthermore, 12 weeks of home-based SPB did not result in significant group x session interaction for upper-and lower-limb muscle strength, nor mobility and dynamic balance. These results suggest that, either with SPB or not, similar outcomes are observed in upper- and lower-limb muscle strength and in mobility and dynamic balance. This could be attributed to the fact that improvements in muscle strength generally require targeted physical exercise involving resistance or load-bearing activities, which stimulate muscular hypertrophy and neuromuscular adaptations (Schoenfeld et al., 2021; Hughes et al., 2018). Similarly, it is possible that enhancements in mobility and dynamic balance require specific training that challenges neuromuscular coordination and functional movement patterns (Wang et al., 2024). Breathing interventions such as SPB primarily enhance autonomic function and oxygen uptake efficiency (Russo et al., 2017), but do not provide the mechanical or neuromuscular stimuli necessary to induce improvements in lower- and upper-limb muscle strength, mobility and dynamic balance. Future research should explore combining SPB with other interventions such as muscle-strengthening exercises or neuromuscular training and consider personalized intensity to maximize functional benefits in middle-aged women.

Our study had some limitations that must be addressed. The findings of this study suggest that 12 weeks of home-based SPB led to improvements in static postural balance and aerobic endurance within the EG. However, these improvements, although encouraging, may reflect non-specific effects or insufficient intervention intensity to generate distinct between-group differences. Similarly, the non-significant group x session interaction for neither upper-and lower-limb muscle strength, nor mobility and dynamic balance may also reflect the limited efficacy of the intervention. Besides, the small sample size, which although determined a priori based on an acute effect study design, may have lacked sufficient power to detect long-term clinically meaningful effects. Additionally, the same breathing frequency was used for all the participants. While this ensured feasibility in a home-based setting and maintained consistency across the sample given resource constraints, it may have limited the intervention's effectiveness. Indeed, it has been claimed that individuals have different optimal breathing frequencies, ranging from 4.5 to 6.5 cycles per minute, and that using heart rate variability biofeedback to identify personalized rates may enhance outcomes (Vaschillo et al., 2006). Hence, using an individual breathing frequency could have induced significant results. Another limitation is the potential influence of postural balance differences between groups at baseline in the EC condition on the foam surface, which may have confounded the results. Although randomization was performed, stratified randomization or statistical adjustment for baseline differences were not applied, warranting cautious interpretation. Moreover, monitoring adherence with more robust tools (e.g., online calls) could have provided a more accurate assessment of participant compliance, potentially leading to better outcomes. Furthermore, the functional tests used in our study (Arm curl test, 30-s Chair Stand, TUG test, and 2-min step test) are part of the Senior Fitness Test developed by Rikli and Jones (1999), which is specifically designed for individuals aged 60 and older. This represents a potential methodological mismatch when applied to women aged 50 to 60 years old, as the test battery may lack sensitivity to detect subtle functional changes in this population. For instance, the 2-Minute Step Test may not fully reflect cardiovascular and respiratory adaptations to SPB, as it does not capture underlying mechanisms such as cardiorepiratory coupling (Roca et al., 2023). Future studies should incorporate comprehensive physiological measures, such as ventilatory analysis (e.g., tidal volume) and oxygen uptake dynamics (e.g., VO₂ kinetics), to better understand physiological adaptations beyond what field-based tests can reveal. Similarly, the TUG test, though a reliable and valuable measure of functional mobility, balance, and fall risk (Nishizawa et al., 2024), and widely used due to its minimal equipment

requirements, could be enhanced by incorporating spatiotemporal gait parameters such as step length variability or cadence (Padulo et al., 2023). Tools like tensiomyography, a non-invasive method for assessing muscle contractile properties such as contraction time and maximal radial displacement of the muscle belly, may also provide deeper insight into neuromuscular adaptations underlying changes in functional performance outcomes, such as endurance, strength, postural balance, and mobility, as they partly rely on these muscle characteristics (Cular et al., 2023; Labata-Lezaun et al., 2023). Moreover, our sample was relatively homogeneous in terms of baseline fitness and health status, this was an intentional methodological choice to minimize variability and enhance internal validity. However, future studies could include participants with more diverse fitness levels to investigate whether baseline cardio-respiratory fitness modulates individual responsiveness to SPB. Finally, the findings of this study should be interpreted with caution when considering their generalizability. The sample comprised post-menopausal middle-aged women from a specific geographic region, which may limit the ability to generalize the results to broader populations or different age groups.

## 5. Conclusion

Our findings indicated that both the middle-aged women who practiced or not the SPB demonstrated similar functional outcomes, suggesting that SPB alone may not be sufficient to induce significant improvements in functional performances. Recent evidence suggests that combining SPB with physical modalities such as Pilates can enhance functional outcomes (Adıgüzel et al., 2023). Therefore, exploring the effects of integrating SPB with muscle-strengthening exercises, neuromuscular training, or flexibility-focused methods like Pilates may yield greater functional benefits and address the limitations of the observed non-significant results.

### CRediT authorship contribution statement

**Karama Masmoudi:** Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.
**Fatma Chaari:** Writing – review & editing, Conceptualization.
**Haithem Rebai:** Writing – review & editing, Conceptualization.
**Sonia Sahli:** Writing – review & editing, Supervision, Conceptualization.

### Funding sources

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Data availability

Data will be made available on request.

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