The purpose of this study is to compare surface and intradermal skin temperature responses to heat stress with and without evaporative and convective cooling.

Humans have important thermoregulatory responses aimed at maintaining body temperature within a narrow range. These responses are driven in part by receptors located in the skin that monitor temperature changes and provide feedback to the central nervous system. Given that skin temperature can affect the physiological responses to heat stress, it is important to accurately measure skin temperature in response to heat stress with and without evaporative (i.e., sweat) and convective (i.e., air flow) cooling. Skin temperature is most often measured on the surface of the skin; however, this temperature can be influenced by other factors such as the local environment. It is unclear how the temperature of the skins surface compares to the temperature within the dermal layer of the skin.

The study team will directly compare skin surface and intradermal temperature responses to heat stress and determine whether these responses area altered by evaporative or convective cooling methods. To accomplish this objective, healthy adults will be exposed to ambient heat stress (no higher than 47°C) with and without evaporative (water sprayed on the skin) and convective (electric fan) cooling. Thermoregulatory responses, inclusive of skin surface and intradermal temperatures, will be assessed throughout the heat trial.

Inclusion Criteria:

• Free of any significant underlying medical problems based upon a detailed medical history and physical exam.
• Normal resting electrocardiogram.

Exclusion Criteria:

• Known heart disease; other chronic medical conditions requiring regular medical therapy including cancer, diabetes, neurological diseases, and uncontrolled hypertension, etc.; as well as serious abnormalities detected on routine screening.
• Individuals who are pregnant, planning to become pregnant, or breastfeeding.
• Taking prescribed medications (such as beta blockers and non-dihydropyridine calcium channel blockers) or over-the-counter medications that have known influences on thermoregulatory response.
• Current smokers, as well as individuals who regularly smoked within the past 3 years.