Exercise and passive heating induce some similar vascular hemodynamic, circulating blood marker, and perceptual responses. However, it remains unknown whether post exercise hot water immersion can synergise exercise derived responses and if they differ from hot water immersion alone. This study investigated the acute responses to post moderate‐intensity exercise hot water immersion (EX+HWI) when compared to exercise (EX+REST) and hot water immersion (HWI+HWI) alone. Sixteen physically inactive middle‐aged adults (nine males and seven females) completed a randomized cross‐over counterbalanced design. Each condition consisted of two 30‐min bouts separated by 10 min of rest. Cycling was set at a power output equivalent to 50% V̇o_{2 peak}. Water temperature was controlled at 40°C up to the mid sternum with arms not submerged. Venous blood samples and artery ultrasound scans were assessed at 0 (baseline), 30 (immediately post stressor one), 70 (immediately post stressor two), and 100 min (recovery). Additional physiological and perceptual measures were assessed at 10‐min intervals. Brachial and superficial femoral artery shear rates were higher after EX+HWI and HWI+HWI when compared with EX+REST (p < 0.001). Plasma nitrite was higher immediately following EX+HWI and HWI+HWI than EX+REST (p < 0.01). Serum interleukin‐6 was higher immediately after EX+HWI compared to EX+REST (p = 0.046). Serum cortisol was lower at 30 min in the HWI+HWI condition in contrast to EX+REST (p = 0.026). EX+HWI and HWI+HWI were more enjoyable than EX+REST (p < 0.05). Irrespective of whether hot water immersion proceeded exercise or heating, hot water immersion enhanced vascular and blood marker responses, while also being more enjoyable than exercise alone.

There is considerable overlap between the mechanisms underlying the health benefits of exercise training and heat therapy. However, it remains unclear whether combining heat therapy with exercise can enhance improvements in cardiovascular and metabolic health. The present study investigated whether post‐exercise hot water immersion (EX+HWI) could augment improvements in cardiorespiratory fitness, cardiovascular and metabolic health compared to post‐exercise thermoneutral water immersion (EX+TWI). Twenty‐four physically inactive middle‐aged adults (age: 58 ± 5 years; body mass index: 28 ± 3 kg m^–2; 13 females) were randomly allocated to 8 weeks of supervised EX+HWI (n = 12) or EX+TWI (n = 12). Moderate‐intensity aerobic exercise (65–75% maximum heart rate) was performed for 30 min followed by 30 min of immersion at 40°C or 34°C, two to four times per week (total 24 sessions). Cardiorespiratory fitness, brachial artery flow‐mediated dilatation, aortic pulse wave velocity, blood pressure and circulating lipids, glucose and inflammatory markers were assessed pre‐ and post‐intervention. Between‐group differences showed that EX+HWI resulted in greater reductions in mean arterial pressure (P = 0.029, η²_p = 0.207, mean difference: –4 mmHg) and an increase in brachial artery flow‐mediated dilatation (P = 0.030, η²_p = 0.206, 2.33%). In addition, there were greater improvements in perceived physical health (P = 0.036, η²_p = 0.211, 5 a.u.). No between‐group differences were observed for cardiorespiratory fitness, aortic stiffness, circulating glucose, lipids and inflammatory markers. Taken together, post‐exercise hot water immersion enhances blood pressure and brachial artery endothelial function, in the absence of improvements in cardiorespiratory fitness, circulating glucose, lipids and inflammatory markers. image Key points: Hot water immersion replicates some of the physiological adaptations to exercise, but it is unclear whether post‐exercise hot water immersion can augment exercise‐derived improvements in cardiovascular health. This is the first study to assess whether 8 weeks of supervised exercise followed by hot water immersion can augment improvements in cardiovascular and metabolic health compared to post‐exercise thermoneutral water immersion in physically inactive middle‐aged adults. We demonstrate that 30 min of moderate‐intensity aerobic exercise, followed by 40°C water immersion, on average three times a week for 8 weeks, reduces diastolic and mean arterial blood pressure more than exercise followed by thermoneutral immersion at 34°C, and increases brachial artery flow‐mediated dilatation. These findings provide novel evidence that post‐exercise hot water immersion lowers diastolic blood pressure and mean arterial pressure, and improves brachial artery endothelial function, without further enhancing cardiorespiratory fitness, glucose, lipids or inflammation in physically inactive middle‐aged adults.

Background and Aims: Arterial function (specifically arterial stiffness) is an important cardiovascular risk factor. Pulse wave velocity (PWV) and augmentation index (Al) are established indicators of arterial function. The present study aimed to evaluate the repeatability and reproducibility of PWV and Al in healthy individuals.Methods: Forty healthy participants (age 33 ± 11 years, 17 females) underwent resting supine PWV and Al assessments. Measurements were made in triplicate and repeated 1 week apart. Al was measured by brachial occlusion and PWV was measured from the carotid artery to the femoral artery via the tonometer‐oscillometric method. Repeatability and reproducibility were assessed using the intraclass correlation coefficient (ICC). Interoperator reproducibility was performed on 10 participants.Results: The average values for week‐to‐week visits for PWV and Al were 6.20 ± 0.91 versus 6.13 ± 0.91 ms⁻¹ and 14.0 ± 11.8 versus 16.3 ± 12.2% respectively. For same‐day measurements, both PWV and Al showed excellent repeatability (PWV: ICC = 0.96, 95% CI: 0.92–0.98, p < 0.01; Al: ICC = 0.90, 95% CI: 0.84–0.94, p < 0.01) and interoperator reproducibility (PWV: ICC = 0.98, 95% CI: 0.93–1.00, p < 0.01; Al: ICC = 0.93, 95% CI: 0.69–0.98, p < 0.01). Measurements were repeated 1 week apart and showed good reproducibility (PWV: ICC = 0.77, 95% CI: 0.61–0.87, p ≤ 0.01; Al: ICC = 0.73, 95% CI: 0.73–0.86, p < 0.01).Conclusion: PWV and Al demonstrate excellent repeatability and good reproducibility. Considering these variables are noninvasive and easy‐to‐measure, arterial function assessment may have a role in routine clinical practice to facilitate risk stratification in cardiovascular diseases.

Repeated hot water immersion can improve cardiovascular health; however, the respective effects of distinct immersion protocols remain unclear. Twenty‐two healthy adults completed three 30‐min hot water immersion bouts of different water temperatures and immersion depths (40°C shoulder‐deep immersion, 40‐Shoulder; 42°C waist‐deep immersion, 42‐Waist; and 40°C waist‐deep immersion, 40‐Waist) in a randomised crossover design. Vascular, inflammatory and perceptual responses were collected via brachial and superficial femoral artery ultrasound, venous blood sampling and perceptual scales. Rectal temperature increased less in the 40‐Waist (Δ0.5 ± 0.1°C) condition than the other conditions (40‐Shoulder: Δ0.9 ± 0.3°C, 42‐Waist: Δ0.9 ± 0.3°C, P < 0.001). Arm skin temperature increased more in the 40‐Shoulder (Δ5.2 ± 1.9°C) condition than the other conditions (40‐Waist: Δ2.6 ± 1.0°C, 42‐Waist: Δ3.6 ± 1.1°C, P < 0.001), whilst thigh temperature had a greater increase in the 42‐Waist (8.6 ± 1.3°C) condition than either the 40‐Waist (7.8 ± 0.2°C) or 40‐Shoulder (Δ7.8 ± 1.0°C) conditions (P < 0.001). Brachial artery shear rate was greatest post‐immersion following the 40‐Shoulder condition (40‐Shoulder: Δ121 ± 94/s, 42‐Waist: Δ47 ± 73/s, 40‐Waist: Δ−21 ± 41/s, P < 0.001) whereas superficial femoral artery shear rate was largest following the 42‐Waist condition (40‐Shoulder: Δ143 ± 61/s, 42‐Waist: 196 ± 85/s, 40‐Waist: 131 ± 93/s, P < 0.001). IL‐6 (P = 0.16) and cortisol (P = 0.83) responses did not differ between conditions. Perceptual responses were more favourable in the 40‐Waist condition. Taken together, these data demonstrate that the distinct region‐specific arterial responses align with increases in local skin temperature to alterations in hot water immersion protocols, whilst showing that beneficial physiological responses may be accompanied with less favourable perceptual responses.