Core Temperature Responses To Exercise Using A Simulated Burn Injury Model

Abstract

BACKGROUND: The US Army’s Standards of Medical Fitness indicate that a burn injury spanning ≥40% of total body surface area (BSA) “does not meet the standard.” While whole-body sweat production and thus evaporation are diminished in burn survivors with extensive skin grafts, the impact of a 40% BSA burn injury on core temperature regulation during exercise is likely dependent on body size, as larger individuals will have a greater absolute skin area that can still participate in heat loss despite the same percentage BSA burn injury. PURPOSE: Using a simulated burn injury model, we tested the hypothesis that the detrimental effect of a 40% BSA “burn injury” would be exacerbated in individuals of smaller versus larger body size during exercise due to a lower absolute (i.e., in m2) skin area available for heat loss. METHODS: On separate occasions, healthy non-burned individuals of small (SM: n=8, 62.4 ± 5.8 kg, 1.69 ± 0.11 m2) or large (LG: n=8, 99.1 ± 8.4 kg, 2.25 ± 0.09 m2) body size cycled to elicit ~500 W of metabolic heat production for 1 h in a 39°C and 20% relative humidity environment with and without (0%) a simulated burn injury of 40% BSA. Burn injuries were simulated by affixing a highly absorbent, vapor-impermeable material to the torso (20% BSA), arms (10% BSA), and legs (10% BSA) to prevent sweat evaporation. Core temperature was measured in the gastrointestinal tract (Tgi). RESULTS: Greater increases in Tgi were observed in SM at 0% (SM: 1.09 ± 0.33°C; LG: 0.64 ± 0.22°C; P=0.03) and 40% (SM: 1.65 ± 0.32°C; LG: 1.14 ± 0.23°C; P=0.01). However, the exacerbated rise in Tgi from 0% to 40% was not different between groups (SM: 0.57 ± 0.28°C; LG: 0.49 ± 0.24°C; P=0.60). CONCLUSIONS: Preliminary data suggest that the exacerbated rise in core temperature with a simulated burn is not dependent on body size. Nevertheless, SM subjects with a simulated burn exercising at the same rate of metabolic heat production experienced the highest absolute Tgi and would therefore be at the greatest risk for a heat-related injury. Funding support: Department of Defense - US Army, W81XWH-15-1-0647.