A Torso Burn Injury Does Not Exacerbate Thermoregulatory Strain During Exercise‐Heat Stress While Wearing A Military Combat Uniform

Abstract

The ability to dissipate heat during exercise is impaired in individuals with grafted skin over a large portion of their body. However, it is unknown whether a torso burn injury impairs thermoregulatory function in uniformed military personnel operating in a hot environment.PurposeTo evaluate whether a torso burn injury exacerbates the rise in core temperature during exercise in a hot environment while wearing a military combat uniform.MethodsTen healthy individuals (8 males) performed 60 min of treadmill walking at 5.3 km/h with 3.7 ± 0.9% grade incline (altered to maintain a rate of metabolic heat generation of ~6.0 W • kg‐1) in a 40.0 ± 0.1 °C and 20.0 ± 0.6% relative humidity climate chamber. On separate, randomized occasions, participants wore a standard U.S. Army Combat Uniform and Outer Tactical Vest (Uniform) with or without a simulated burn injury imposed by placing absorbent vapor‐impermeable material across the torso, 20% body surface area (BSA), to hinder evaporative heat dissipation (Uniform + Burn). A third trial was conducted without the uniform or simulated burn with subjects wearing athletic shorts and sports bra for females (Control).Rectal temperature and heart rate were monitored continuously, and metabolic heat production was calculated via indirect calorimetry. The change in outcome measures from baseline to the end of exercise were compared between trials with a two‐way (group × time) repeated‐measures ANOVA.ResultsAt the end of exercise, no differences were revealed (P > 0.05) between the Uniform versus Uniform + Burn trials in all outcome variables: increase in rectal temperature (Uniform: Δ1.16 ± 0.3°C; Uniform + Burn: Δ1.21 ± 0.4°C), thermal sensation (Uniform: 6.0 ± 0.6; Uniform + Burn: 6.2 ± 0.8), rating of perceived exertion (Uniform: 14.2 ± 2.7; Uniform + Burn: 14.1 ± 3.0) and increase in heart rate (Uniform: Δ61 ± 13; Uniform + Burn: Δ56 ± 15 bpm). In contrast, the Control trial showed lower (P < 0.05): increases in rectal temperature (Δ0.93 ± 0.3°C), thermal sensation (4.8 ± 0.7), rating of perceived exertion (11.3 ± 2.2), and increases in heart rate (Δ44 ± 14 bpm) compared to both the Uniform and Uniform + Burn trials.ConclusionA 20% BSA simulated burn on the torso does not exacerbate thermoregulatory strain during exercise in a hot environment while wearing a military combat uniform in healthy young adults. These findings suggest that the risk of heat‐related illness in soldiers with torso burn injuries is no different than non‐injured soldiers when wearing a standard military combat uniform.Support or Funding InformationThis work was supported by awards from the Department of Defense (W81XWH‐15‐1‐0647 to CGC), National Institutes of Health (R01GM068865 to CGC), and a Natural Sciences and Engineering Research Council of Canada Postdoctoral Fellowship (to MNC).