Whole-Body Heat Loss during Exercise in the Heat Is Not Impaired in Type 1 Diabetes.

Purpose: To determine if individuals with type 1 diabetes exhibit impairments in local and whole-body heat loss responses that could impact core temperature regulation during exercise in the heat compared to matched, non-diabetic individuals. Methods: Twelve otherwise healthy individuals with type 1 diabetes (HbA1c = 7.7±0.3%) and 12 controls matched for age, sex, body surface area, and physical fitness cycled continuously for 60-min at a set rate of metabolic heat production (∼400W) in a whole-body direct calorimeter (35 °C and 20% relative humidity). Local sweat rate (ventilated capsule) was measured on the back and skin blood flow (SkBF, laser-Doppler velocimetry) on the forearm. Core (rectal and esophageal) and mean skin temperatures and heart rate were measured continuously. Whole-body heat exchange and change in body heat content were measured using simultaneous direct whole-body and indirect calorimetry. Results: The change (mean±SE) in body heat content was similar between groups during exercise (Diabetes: 409±27; Control: 386±33 kJ, p=0.584) and recovery (Diabetes:-115±16; Control:-93±24 kJ, p=0.457). Local heat loss responses of sweating (p=0.783) and SkBF (p=0.078), as well as rectal temperature (Diabetes: 37.87±0.10; Control: 37.85±0.13 °C, p=0.977) and heart rate (Diabetes: 130±9 vs. Control: 127±7 beats·min, p=0.326) were comparable at the end of the exercise period. Conclusion: During light-to-moderate intensity exercise performed under conditions permitting full sweat evaporation, otherwise healthy type 1 diabetic individuals did not show impaired heat loss responses during heat exposure when compared to matched individuals without diabetes.