Burn Injury Does Not Exacerbate Heat Strain during Exercise while Wearing Body Armor

Abstract

Introduction: Although evaporative heat loss capacity is reduced in burn-injured individuals with extensive skin grafts, the thermoregulatory strain due to a prior burn injury during exercise-heat stress may be negligible if the burn is located underneath protective clothing with low vapor permeability.

Purpose: This study aimed to test the hypothesis that heat strain during exercise in a hot-dry environment while wearing protective clothing would be similar with and without a simulated torso burn injury.

Methods: Ten healthy individuals (8 men/2 women) underwent three trials wearing: uniform (combat uniform, tactical vest, and replica torso armor plates), uniform with a 20% total body surface area simulated torso burn (uniform + burn), or shorts (and sports bra) only (control). Exercise consisted of treadmill walking (5.3 km·h; 3.7% ± 0.9% grade) for 60 min at a target heat production of 6.0 W·kg in 40.0°C ± 0.1°C and 20.0% ± 0.6% relative humidity conditions. Measurements included rectal temperature, heart rate, ratings of perceived exertion (RPE), and thermal sensation.

Results: No differences in rectal temperature (P ≥ 0.85), heart rate (P ≥ 0.99), thermal sensation (P ≥ 0.73), or RPE (P ≥ 0.13) occurred between uniform + burn and uniform trials. In the control trial, however, core temperature, heart rate, thermal sensation, and RPE were lower compared with the uniform and uniform + burn trials (P ≤ 0.04 for all).

Conclusions: A 20% total body surface area simulated torso burn injury does not further exacerbate heat strain when wearing a combat uniform. These findings suggest that the physiological strain associated with torso burn injuries is not different from noninjured individuals when wearing protective clothing during an acute exercise-heat stress.

Figure 1—

The change in core temperature (left) and heart rate (right) throughout exercise at 40°C and 20% RH while wearing a military combat uniform (Uniform), a military combat uniform with a simulated burn injury (Uniform + Burn), or shorts and shoes with females also wearing a sports bra (Control). * difference between Control and Uniform + Burn (P < 0.05). † difference between Control and Uniform (P < 0.05). Values are mean ± SD for 10 participants.

Figure 2—

Rating of perceived exertion (left) and thermal sensation (right) throughout exercise at 40°C and 20% RH while wearing a military combat uniform (Uniform), a military combat uniform with a simulated burn injury (Uniform + Burn), or shorts and shoes with females also wearing a sports bra (Control). * difference between Control and Uniform + Burn (P < 0.02). † difference between Control and Uniform (P < 0.05). ¥ main effect differences between Control and both Uniform and Uniform + Burn for thermal sensation. There were no main effect differences between Uniform and Uniform + Burn for this variable. Values are mean ± SD for 10 participants.