Nongrafted Skin Area Best Predicts Exercise Core Temperature Responses in Burned Humans

Grafted skin impairs heat dissipation, but it is unknown to what extent this affects body temperature during exercise in the heat. Purpose We examined core body temperature responses during exercise in the heat in a group of individuals with a large range of grafts covering their body surface area (BSA; 0%-75%). Methods Forty-three individuals (19 females) were stratified into groups based on BSA grafted: control (0% grafted, n = 9), 17%-40% (n = 19), and >40% (n = 15). Subjects exercised at a fixed rate of metabolic heat production (339 +/- 70 W; 4.3 +/- 0.8 Wkg(-1)) in an environmental chamber set at 40 degrees C, 30% relative humidity for 90 min or until exhaustion (n = 8). Whole-body sweat rate and core temperatures were measured. Results Whole-body sweat rates were similar between the groups (control: 14.7 +/- 3.4 mLmin(-1), 17%-40%: 12.6 +/- 4.0 mLmin(-1); and >40%: 11.7 +/- 4.4 mLmin(-1); P > 0.05), but the increase in core temperature at the end of exercise in the >40% BSA grafted group (1.6 degrees C +/- 0.5 degrees C) was greater than the 17%-40% (1.2 degrees C +/- 0.3 degrees C) and control (0.9 degrees C +/- 0.2 degrees C) groups (P < 0.05). Absolute BSA of nongrafted skin (expressed in square meters) was the strongest independent predictor of the core temperature increase (r(2) = 0.41). When regrouping all subjects, individuals with the lowest BSA of nongrafted skin (<1.0 m(2)) had greater increases in core temperature (1.6 degrees C +/- 0.5 degrees C) than those with more than 1.5 m(2) nongrafted skin (1.0 degrees C +/- 0.3 degrees C; P < 0.05). Conclusions These data imply that individuals with grafted skin have greater increases in core temperature when exercising in the heat and that the magnitude of this increase is best explained by the amount of nongrafted skin available for heat dissipation.