Description:
<jats:p>Following a burn injury, excision of injured skin and subsequent grafting lead to attenuated sweating rates and thereby a diminished capacity for evaporative heat loss, resulting in exacerbated elevations in core temperature and greater risk of heat illness during physical activities. Since the capacity for evaporation is dependent on the absolute area of non‐injured body surface area (BSA), and the heat load imposed on the body reflects both metabolic and environmental sources of heat gain, the detrimental effect of a burn injury on core temperature regulation during exercise at a given intensity is likely dependent on the interaction between the size of a burn injury and the prevailing air temperature. To test this possibility, four healthy males (23 ± 3 years, 80.1 ± 11.1 kg, 1.98 ± 0.15 m<jats:sup>2</jats:sup>) visited the laboratory on eight occasions to complete 1 h of cycling at a fixed rate of metabolic heat production (~6 W/kg; indirect calorimetry) in a 39°C or 24°C environment (20% relative humidity) with a simulated burn injury of 0%, 20%, 40%, or 60% BSA. Burn injuries were simulated by covering skin on the torso, arms, and legs with highly absorbent, vapor‐impermeable material that impedes sweat evaporation. Core temperature was measured in the gastrointestinal tract (T<jats:sub>gi</jats:sub>). Elevations in T<jats:sub>gi</jats:sub> at 24°C were not different across all simulated burn injury levels (0%: 0.81 ± 0.13°C, 20%: 0.70 ± 0.20°C, 40%: 0.78 ± 0.14°C, 60%: 0.65 ± 0.16°C; P ≥ 0.32). At 39°C, the increase in T<jats:sub>gi</jats:sub> was not different between 0% (0.83 ± 0.24°C), 20% (0.96 ± 0.35°C), and 40% (0.99 ± 0.15°C) simulated burn injuries (P ≥ 0.60), but the rise in T<jats:sub>gi</jats:sub> with a 60% simulated burn injury (1.84 ± 0.16°C) was greater than the other “injury” levels (P<0.05). Consistent with this observation, elevations in T<jats:sub>gi</jats:sub> were exacerbated at 39°C <jats:italic>versus</jats:italic> 24°C only with a 60% simulated burn injury (P<0.01). In summary, core temperature reached similarly elevated levels following 1 h of moderate‐intensity exercise with simulated burn injuries of 20%, 40%, and 60% of BSA under temperate environmental conditions, and with simulated burn injuries of 20% and 40% in hot conditions. However, exercise in the heat at the same intensity with a 60% BSA simulated burn injury resulted in a greatly exacerbated elevation in T<jats:sub>gi</jats:sub>. Therefore, burn survivors with injuries spanning 60% of total BSA may be exposed to a greater risk of hyperthermia and heat illness when working at a fixed intensity in a hot environment.</jats:p><jats:p><jats:bold>Support or Funding Information</jats:bold></jats:p><jats:p><jats:italic>Funding: Department of Defense – US Army, W81XWH‐15‐1‐0647</jats:italic></jats:p>