Reflective inserts to reduce heat strain in body armor: tests with and without irradiance.

BACKGROUND This study evaluated adding reflective thermal inserts (RTI) to reduce the physiological strain during exercise-heat stress with a radiant load. RTI were used with a U.S. Army desert battle dress uniform, body armor, and helmet. METHODS Four male volunteers attempted four trials (10 min rest followed by 100 min walking at 1.56 m x s(-1)). All trials were at 40.0 degrees C dry bulb (Tdb), 12.4 degrees C dew point (Tdp), 20% RH, and 1.0 m x s(-1) wind speed. On 2 d, there was supplementary irradiance (+1) with globe temperature (Tbg) = 56.5 degrees C and on 2 d there was no supplementary irradiance (-I) with Tbg approximately Tdb. Trial conditions were: 1) RTI and armor with supplementary irradiance (RA+I); 2) plain armor with supplementary irradiance (PA+I); 3) RTI and armor with no supplementary irradiance (RA-I); and 4) plain armor with no supplementary irradiance (PA-I). RESULTS Endurance times were not significantly different among trials. With one exception, armor and helmet interior and exterior surface temperatures were not significantly different between either RA+I and PA+I or RA-I and PA-I. Temperature on the inside of the helmet in RA+I (47.1 +/- 1.4 degrees C) was significantly lower than in PA+I (49.5 +/- 2.6 degrees C). There were no differences for any physiological measure (core temperature, heart rate, mean weighted skin temperature, forehead skin temperature, sweating rate, evaporative cooling, rate of heat storage) between either RA+I and PA+L or RA-I and PA-I. CONCLUSIONS Results showed no evidence that wearing RTI with body armor and helmet reduces physiological strain during exercise-heat stress with either high or low irradiance.