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

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.

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