Primary aging is associated with impairments in the body's responses to heat stress. Additionally, higher body mass may be associated with reduced tolerance to heat stress. Adults over the age of 65 are the most at-risk population for heat-related illness; however, less is known about the development of such vulnerability in middle-aged adults. This study aims to characterize heat stress responses in middle-aged adults (aged 40-65 yrs) with body mass index (BMI)>30 and BMI<25 during whole-body heating.

There will be two in-person visits. The first visit is a screening visit that will last a maximum of 1.5 hours, during which we measure your height, weight, blood pressure, and collect a blood sample to check markers of health. The second visit is an experimental visit, during which you will lie in a hospital bed wearing a tub-lined suit through which warm water flows, heating up your body. We measure your internal body temperature with an ingestible pill, and we measure skin temperature with probes that we tape to the skin. During the body heating period, we measure your skin blood flow and sweat rate with small probes and capsules, respectively, that are placed on your forearm.

$60