The Effects of 8 Weeks Post Exercise Hot Water Immersion on Vascular and Cardiometabolic Health in Physically Inactive Middle-aged Adults

Study Overview
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Brief Summary
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This research project aims to determine whether post exercise hot water immersion can improve vascular and cardiometabolic health to a greater extent than post exercise thermoneutral water immersion in healthy middle-aged adults. The study will take place over an 8 week period where participants will do a combination of aerobic exercise and water immersion 3 times per week. The study will be a randomised controlled trial comparing 8-weeks of post exercise hot water immersion (EX+HWI) to post exercise thermoneutral water immersion (EX+TNWI).

Detailed Description
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The exercise component of each intervention will be 30 minutes of moderate intensity aerobic exercise consisting of 10 minutes cycling, jogging and rowing, three times per week. Exercise intensity will be maintained at a heart rate equivalent of 65% of maximal heart rate. All exercise sessions will take the form of supervised group exercise sessions (<4 participants) at Coventry University. After 30 minutes of exercise, participants will either complete 30 minutes of whole-body hot water immersion at 40°C or thermoneutral immersion at 34°C in the control condition (similar protocols are known to be well tolerated in older adults) (Akerman et al. 2019; Brunt et al. 2016). In order to ensure progression, exercise intensity will be increase to 75% of maximal heart rate according to the maximal exercise test at 4 weeks. Assessment sessions will take place before session 1 and >48hrs after session 12 and 24. Prior to arriving at the lab participants will complete an overnight fast. Participants will also refrain from consuming alcoholic and caffeinated beverages, nitrate high sources and any form of strenuous exercise in the 24hr time period prior to testing. All testing laboratory visits will be completed in the morning and where possible at the same time of day to help standardise for any potential variations that the circadian rhythm may have on the measured variables. Assessments will be completed over two days. The outcome measures for this study comprise a range of physiological psychological measures which are known to inform the risk of cardiovascular disease. These measures fall into the following broad categories 1) vascular health; 2) cardiometabolic and inflammatory blood markers; 3) maximal exercise test and 4) cardiovascular disease risk prediction. In addition, measures of intervention acceptability and basic physiological heat acclimation measures will also be assessed.

Official Title
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The Effects of 8 Weeks Post Exercise Hot Water Immersion on Vascular and Cardiometabolic Health in Physically Inactive Middle-aged Adults

Conditions
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Physical Inactivity, Aging

Intervention / Treatment
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* Other: Aerobic exercise + hot water immersion
* Other: Aerobic exercise + thermoneutral water immersion


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged between 45 - 65 years If female and post-menopausal (12 months without a period and not taking HRT) Body mass index (BMI) 18.5 - 34.9kg/m2 Participated in less than 150 mins of moderate intensity physical activity or 75 mins of vigorous or a combination of both over the last 6 months. Exclusion Criteria: Previous myocardial infarction or cerebrovascular event Any signs or symptoms of cardiovascular issues High blood pressure: SBP >180 mmHg and / or DBP >100 mmHg Orthostatic hypotension: Drop of SBP > 20mmHg and / or DBP >10 mmHg upon standing. Changed blood pressure medication in the 6-month period prior to the study Plan to change any form of relevant medication during study period Suffers from diabetes Suffers from severe asthma Currently have any infections or symptoms of an infection (e.g. COVID-19 etc) Suffers from a neurodegenerative disease Cannot understand and/or fully cooperate with the study protocol Exercise-limiting comorbidity (e.g. angina, chronic lung disease, arthritis etc) Severe peripheral neuropathy (cannot sense temperature) Current smoker or have stopped in the last 3 months Any skin conditions including ulcerations Exposed to high temperatures in the last 4-weeks (e.g. holiday, spa, sun beds etc) Use of antioxidant supplements in the last 6-weeks

Ages Eligible for Study
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Minimum Age: 45 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Aerobic exercise + hot water immersion<br>3 sessions per week, over an 8 week period, with each session consisting of 30 minutes of aerobic exercise (10 minutes cycling, jogging and rowing) at a power output equivalent to 65-75% of maximal heart rate followed by 30 minutes of whole body hot water immersion at 40°C. | Other: Aerobic exercise + hot water immersion<br>* Light to moderate intensity aerobic exercise for 30 minutes, followed by 30 minutes of hot water immersion at 40°C.<br>|
| Active Comparator: Aerobic exercise + thermoneutral water immersion<br>3 sessions per week, over an 8 week period, with each session consisting of 30 minutes of aerobic exercise (10 minutes cycling, jogging and rowing) at a power output equivalent to 65-75% of maximal heart rate followed by 30 minutes of whole body water immersion at 34°C. | Other: Aerobic exercise + thermoneutral water immersion<br>* Light to moderate intensity aerobic exercise for 30 minutes, followed by 30 minutes of thermoneutral water immersion at 34°C.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in resting systolic blood pressure (mmHg) | Measured using an automated blood pressure cuff | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in resting diastolic blood pressure (mmHg) | Measured using an automated blood pressure cuff | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in resting mean arterial blood pressure (mmHg) | Measured using an automated blood pressure cuff | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in flow mediated dilation (%) | Terason ultrasound recording after brachial artery occlusion | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in pulse wave velocity (ms-1) | SphygmoCor XCEL measuring carotid to femoral arterial stiffness | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in intima-media thickness (mm) | Terason ultrasound image to measure wall thickness from the lumen-intima interface to the media-adventitia interface of the brachial and femoral arteries | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in beta stifnness index | Calculated using systolic, diastolic blood pressure from automated blood pressure cuff and vessel diameter from Terason ultrasound image of brachial and femoral arteries | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in dynamic arterial compliance (mm2) | Calculated using pulse pressure from automated blood pressure cuff and vessel diameter from Terasol ultrasound image of brachial and femoral arteries | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in maximal oxygen uptake (ml/kg/min) | Maximal oxygen uptake | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in glucose tolerance (mmol/L) | Oral glucose tolerance test through fingertip capillary blood samples at 15 minute intervals for the first 1 hour and 30 minute intervals for the second hour | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum Interleukin-6 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum TNF-α (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum Interleukin-8 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum Interleukin-10 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum Interleukin-1Ra (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating Endothelin-1 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Circulating serum Monocyte chemoattractant protein-1 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum Matrix metallopeptidase-2 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating serum Matrix metallopeptidase-9 (pg/ml) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating total cholesterol (mmol/L) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating low density lipoproteins (mmol/L) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating high density lipoproteins (mmol/L) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating Triglycerides (mmol/L) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating glycated haemoglobin (%) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in circulating basal glucose (mmol/L) | Venous blood sample | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Framingham risk score | Calculation based on age, gender, total cholesterol, HDL cholesterol, smoker, diabetes status and systolic blood pressure | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in rectal core temperature (°C) | Measured using a rectal probe attached to a squirrel data logger | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in resting heart rate (bpm) | Measured using a heart rate monitor | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Body mass index (kg/m²) | Calculated through height and weight | Measurements taken the week before the study, >48hrs after 4 weeks and >48hrs after 8 weeks | 
| Change in thermal comfort | Thermal comfort Likert scale from a positive score of +5 very comfortable (maximum) to a negative score of -5 very uncomfortable (minimum) | Measurements taken pre and post visit 1, 12 (4 weeks) and 24 (8 weeks) | 
| Change in thermal sensation | Thermal sensation Likert scale from a positive score of +5 hot (maximum) to a negative score of -5 cold (minimum) | Measurements taken pre and post visit 1, 12 (4 weeks) and 24 (8 weeks) | 
| Change in basic affect | Basic affect Likert scale from a positive score of +5 very good (maximum) to a negative score of -5 very bad (minimum) | Measurements taken pre and post visit 1, 12 (4 weeks) and 24 (8 weeks) | 
| Change in physical activity enjoyment | Feelings about exercise and / or passive heating on a Likert scale from a positive score of 1 (maximum) to a negative score of 7 (minimum) | Measurements taken pre and post visit 1, 12 (4 weeks) and 24 (8 weeks) |