Aging and obesity are independently associated with impairments in the body's responses to heat stress. However, the compounding effects of middle age and obesity on those responses during heat stress at rest or during physical activity have not investigated in obese, middle-aged individuals. This study aims to characterize heat stress responses in obese vs. non-obese middle-aged adults (aged 40-65 yrs) during passive (resting) and active (light physical activity) whole-body heat stress.

There will be five 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 a maximal exercise test which will last approximately 1 hour, during which you will perform an incremental exercise test on a treadmill. The other three visits are experimental visits. During one of those visits, 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. During the other two visits, you perform light physical activity on a recumbent bicycle in a hot environment while we monitor your body temperature.

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