Preparing for Heat Waves - Enhancing Human Thermophysiological Resilience

A non-randomized, within-subject experimental trial will be conducted. The complete study will consist of a screening day, a control week, a heat acclimation week, 3 heat stress test (HST) and meal-test (MT) days (t = -7, 0, and 8 (days)). To avoid a confounding effect of seasonal thermal differences and achieve maximal methodological quality, the study will be performed in the shortest possible timeframe for each participant. Given the seasonal fluctuations in NL, transitioning from April (\~7oC) to June (\~20oC), a crossover design is not applicable as a washout period of approximately 2 months would be needed and the measurements would likely take place in different climatic outdoor conditions. In total, 12 healthy male and female participants will be included in the study. During the no-intervention week (week 1), participants will be asked to continue their normal life at home, without being present at the university. In addition, during week 1, participants will be asked to wear a temperature sensor on their clothing to measure the environment temperature they are exposed to at home. Thereafter, on the intervention week (week 2), participants will be exposed to increasing elevated temperatures and undergo 30 min of low-to-moderate intensity cycling in the heated laboratory room for 7 days. The temperature settings are derived from past heat waves in the Netherlands, ensuring a realistic representation. The low exercise intensity is selected to be accessible to the majority of individuals within the target population. The HST-MT will be conducted on the first visit after the screening to serve as baseline measurements. The same tests will also be repeated before and after the heat acclimation week to determine the physiological response to increasing ambient temperatures. All measurements will take place in the Metabolic Research Unit of Maastricht University (MRUM), the Netherlands.