Author(s): STEWARD, C., HILL, M., MENZIES, C., RUSSELL, S., PUGH, C., THAKE, D., CULLEN, T., Institution: COVENTRY UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 642

INTRODUCTION:
Heat therapy can replicate some of the long-term adaptations of exercise training which underpin improvements in cardiovascular health [1]. It is estimated that 25% of adults do not meet the minimum recommended physical activity guidelines [2]. However, many take part in irregular, less intense and infrequent bouts of physical activity within their weekly routines. The use of hot water immersion after exercise has the potential to augment the cardiovascular health benefits from smaller amounts of exercise. Therefore, this study investigated whether post exercise hot water immersion (EX+HWI) can improve cardiovascular health by a greater extent than post exercise thermoneutral water immersion (EX+TNWI).

METHODS:
After ethical approval, twenty-four physically inactive middle-aged adults (14 females and 10 males; age: 58 ± 5 years; weight: 78 ± 12 kg; height: 1.67 ± 0.08 m; V̇O2 peak: 18 ± 3 ml/kg/min-1) were randomised to either 8-weeks of EX+HWI (n=12) or EX+TNWI (n=12). Volunteers visited the laboratory 2-4 times per week to take part in exercise plus immersion sessions (total 24 sessions). The exercise component was for a duration of 30 minutes and consisted of 10 minutes cycling, rowing and brisk walking at 65%-75% of heart rate maximum. Water immersion was for 30 minutes at a temperature of either 40 °C or 34 °C. A range of cardiovascular health parameters were measured pre, midway and post intervention, including cardiorespiratory fitness, blood pressure, brachial artery endothelial function, carotid to femoral arterial stiffness and serum cardiometabolic/inflammatory biomarkers.

RESULTS:
A time × condition interaction was detected for mean arterial pressure (P=0.039) and diastolic blood pressure (P=0.044). EX+HWI resulted in a greater reduction in mean arterial pressure and diastolic blood pressure at midway (MAP: P<0.001, mean difference= 5 mmHg and DBP: P=0.001, mean difference=5 mmHg) and post (MAP: P=0.011, mean difference= 4 mmHg and DBP: P=0.007, mean difference=4 mmHg) intervention in comparison to EX+TNWI. Furthermore, a main effect of condition was apparent for systolic blood pressure (P=0.003, mean difference=4 mmHg) and central arterial stiffness (P=0.048, mean difference=2.08 m/s). There were no differences between conditions for cardiorespiratory fitness, brachial artery endothelial function and serum cardiometabolic/inflammatory biomarkers (P>0.05).

CONCLUSION:
Eight weeks of post exercise hot water immersion improved vascular health through reducing blood pressure and central artery stiffness to a greater extent than exercise followed by thermoneutral water immersion in physically inactive middle-aged adults.