Effect of air-filled vest on exercise-heat strain when wearing ballistic protection

Abstract

Objectives: The purpose was to determine if an air-filled vest worn under ballistic protection reduces physiological strain during exercise in the heat either while wearing a tactical military (TM) protective vest or a law enforcement (LE) concealable vest. Methods: Sixteen men (24.5±3.9 years; 179.5±5.6cm; 84.6±12.3kg) performed either two or four trials of treadmill walking (1.34 m s-1; 2% grade) over 120min in a hot, dry environment (37°C, 30% relative humidity, wind speed 3.5 m s-1). Participants completed trials wearing a TM or LE, with either the air-filled vest (TMa; LEa) or no vest (TMc; LEc) in random order. During trials, participants wore Army Combat Uniform pants. Physiological variables measured every 5min included gastrointestinal temperature (T GI), mean skin temperature (T sk), and heart rate (HR). Sweat rate (SR) was calculated based on fluid intake and body mass measures. Results: In the tactical trial (TMa versus TMc), no differences in final T GI (38.2±0.4 versus 38.3±0.4°C), T sk (35.0±0.9 versus 35.0±1.0°C), HR (142±19 versus 143±23 bpm) existed (P > 0.05). In the LE trials (LEa versus LEc), no differences in final T GI (38.0±0.4 versus 38.1±0.3°C), T sk (35.3±1.1 versus 35.6±0.9°C), HR (132±20 versus 135±20 bpm) existed (P > 0.05). Despite slightly higher SR, there was no statistical difference in TM (1.15±1.13 versus 1.54±0.46 l h-1; P = 0.10) or in LE (1.39±0.52 versus 1.37±0.18 l h-1; P = 0.35) during trials. Conclusion: When participants exercised with a TM or LE while wearing the air-filled vest, there were no thermoregulatory and physiological differences compared to control trials. In our testing conditions, the air-filled device had little effect on physiological responses during prolonged mild exercise in the heat.