Identifying the Upper Environmental Limits of Thermal Compensation in Older Human Females Using a Rapid Humidity Ramp Protocol

What this Trial Is About

Researchers are studying how extreme heat affects older females aged 65 to 85 years, focusing on their ability to lose heat compared to males. This study aims to understand when heat stress becomes too great for their bodies to handle, known as the limit of compensability, and how this relates to risks of heat-related illness. The research will assess physical, psychological, and cognitive responses to different heat conditions using a ramping protocol and fixed heat exposures. Participants will undergo five trials, starting with a humidity-ramp protocol where they rest in warm conditions (42°C, 28% humidity) and then experience gradual increases in humidity until a critical point is reached. Subsequent trials expose participants to fixed humidity levels set around this critical point, including levels below, above, and a control thermo-neutral condition. Each fixed exposure lasts up to 9 hours with water provided to reduce dehydration risk. The order of the fixed exposures is randomized after completing the ramping protocol. During the study, researchers will monitor core temperature changes, heart rate, sweat rate, thermal comfort, mood, and environmental symptoms. They will track how quickly body temperature rises and measure cumulative strain under different heat conditions. The study also evaluates how many participants can complete each exposure and assesses psychological and cognitive effects. Participation involves repeated visits over the study period, with continuous monitoring to understand heat tolerance in older females better.

Identifying the Limits of Survivability in Heat-exposed Older Females