Comparison of Acute Sauna With Exercise and Sauna

Overview

Sauna bathing has been associated with a lower risk for cardiovascular disease (CVD) outcomes, improved vascular endothelial and cardiac function, reduced oxidative stress and lower blood pressure. Earlier studies conducted by the investigators have showed positive alterations of arterial stiffness and hemodynamics through sauna bathing. Some studies have sought to utilize sauna bathing as an intervention after exercise with promising and synergistic results, although the effects on populations with cardiovascular risk factors are less clear. Furthermore, studies investigating the use of both exercise and sauna bathing in combination has been somewhat limited. However, results from some studies speculate that adjunctive exercise and sauna interventions may be useful for aging and clinical patient population groups. Given that heat therapy and sauna use is gaining more worldwide popularity, the investigators sought to compare the acute hemodynamic effects between sauna use alone and a short bout of exercise followed by sauna exposure. It was hypothesize that the combination of exercise and sauna will elicit greater changes than sauna alone. To achieve this, we standardized the protocol duration (30 minutes).

In this crossover trial, all study participants underwent two interventions, each on a separate occasion (\>72 hours apart). A standalone 30-minute sauna at 75°C (S), and 15-minutes of cycling on the stationary bike at 75% maximum heart rate, followed by 15-minutes of sauna exposure (ES). A cycling exercise test was conducted on a separate day prior to the experiment to ascertain individual maximal exercise heart rates, which was then used to calculate individual 75% maximum. After the first 15-minute period of S, the participants left the sauna room to have a quick shower (\<30 seconds) before going back for the second 15-minute period. The same sauna bathing room (75°C) was used for all participants and the cycling exercise was conducted within 10 meters of the sauna room to minimize transit time during ES. Participants were instructed to abstain from eating 2h, caffeine 12h and alcohol 24h prior to the measurements. Food intake was not standardized. Fluid was consumed ad libitum. A medical physician was in attendance at all times and participants were allowed to leave the sauna or stop the experiment at any time if they felt uncomfortable. Brachial blood pressures and pulse wave velocity (PWV) as a measure of arterial stiffness, were taken in their respective order at three different time points; before (PRE), immediately after (POST), and after a 30-minute recovery (POST30). Transit time from the cessation of the intervention to POST measurements were kept under 60 seconds. All measurements were performed by the same assessor to minimize ascertainment biases. Participants were permitted to take a quick shower (\<30 seconds) before POST measurements were taken. Water temperature or the shower was not controlled and participants could freely select their desired temperature. Thereafter, they were instructed to rest in a designated waiting lounge (mean temperature 21°C) in a seated position for a duration of 30-minutes before the last measurement (POST30) was taken.