Effect of Air-Filled Vest on Exercise-Heat Strain When Wearing Ballistic Protection

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 +/- 5.6 cm; 84.6 +/- 12.3 kg) performed either two or four trials of treadmill walking (1.34 m s(-1); 2% grade) over 120 min in a hot, dry environment (37 degrees 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 5 min 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 degrees C), T-sk (35.0 +/- 0.9 versus 35.0 +/- 1.0 degrees 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 degrees C), T-sk (35.3 +/- 1.1 versus 35.6 +/- 0.9 degrees 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.