The Effects of Post Aerobic Exercise Hot Water Immersion on Physiological and Perceptual Responses in Physically Inactive Middle-aged Adults

A large number of middle aged adults do not achieve the minimum recommended amount of physical activity. This consequently increases the risk of cardiovascular disease and all-cause mortality. Although below the recommended physical activity guidelines, it is important to highlight that a considerable proportion of these individuals do take part in some form of physical activity within their weekly routines. Hence, identifying complementary therapies that can enhance the health benefits from smaller amounts of exercise are of great value for many physically inactive middle-aged adults.

An in increase in body temperature from a single session of passive heating has been shown to mimic many of the beneficial physiological responses of exercise, such as, an increase in heart rate, skin blood flow and an increase in circulating angiogenic factors. However, lab based studies often push participants to the limit of thermal tolerance which may reduce long term adherence in the real world. Therefore, this study will investigate whether the use of post exercise hot water immersion can prolong and / or intensify exercise mediated physiological responses that underpin health benefits, whilst also assessing the perceptual responses, in comparison to exercise and hot water immersion alone.

Through the use of a repeated measures design, participants will randomly take part in three conditions; 1) post exercise hot water immersion (30 minutes of moderate intensity cycling followed by 10 minutes of supine rest and 30 minutes of whole body hot water immersion at 40°C); 2) aerobic exercise (30 minutes of moderate intensity cycling followed by 10 minutes of supine rest and 30 minutes of seated rest at room temperature); 3) hot water immersion condition (30 minutes of whole body hot water immersion at 40°C followed by 10 minutes of supine rest and 30 minutes of whole body hot water immersion at 40°C). Each condition will be separated by a minimum of 1-week. Outcome measures will either be assessed at regular intervals or at 0, 30, 70 and 100 minute time points for each condition.

Inclusion criteria

• Males and post menopausal females
• Aged between 40 - 60 years
• BMI of 18.5 - 34.9 kg/m2
• Over the last 6 months has participated in less than 150 mins of moderate intensity physical activity or 75 mins of vigorous activity or a combination of both, but takes part in some form of physical activity within their weekly routine.
• Maximal oxygen uptake categorised as 'fair' for a given age group.

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