Burn size and environmental conditions modify thermoregulatory responses to exercise in burn survivors

This project tested the hypothesis that burn survivors can perform mild/moderate-intensity exercise in temperate and hot environments without excessive elevations in core body temperature. Burn survivors with low (23 +/- 5%TBSA; N = 11), moderate (40 +/- 5%TBSA; N = 9), and high (60 +/- 8%TBSA; N = 9) burn injuries performed 60 minutes of cycle ergometry exercise (72 +/- 15 watts) in a 25 degrees C and 23% relative humidity environment (ie, temperate) and in a 40 degrees C and 21% relative humidity environment (ie, hot). Absolute gastrointestinal temperatures (T-GI) and changes in T-GI (Delta T-GI) were obtained. Participants with an absolute T-GI of >38.5 degrees C and/ or a Delta T-GI of >1.5 degrees C were categorized as being at risk for hyperthermia. For the temperate environment, exercise increased Delta T-GI in all groups (low: 0.72 +/- 0.21 degrees C, moderate: 0.42 +/- 0.22 degrees C, and high: 0.77 +/- 0.25 degrees C; all P < .01 from pre-exercise baselines), resulting in similar absolute end-exercise T-GI values (P = .19). Importantly, no participant was categorized as being at risk for hyperthermia, based upon the aforementioned criteria. For the hot environment, Delta T-GI at the end of the exercise bout was greater for the high group when compared to the low group (P = .049). Notably, 33% of the moderate cohort and 56% of the high cohort reached or exceeded a core temperature of 38.5 degrees C, while none in the low cohort exceeded this threshold. These data suggest that individuals with a substantial %TBSA burned can perform mild/moderate intensity exercise for 60 minutes in temperate environmental conditions without risk of excessive elevations in T-GI. Conversely, the risk of excessive elevations in T-GI during mild/moderate intensity exercise in a hot environment increases with the %TBSA burned.