A comparison of three liquid-ventilation cooling garments during treadmill exercise

Tests were performed on five male subjects to compare the heat transfer performance and physiological effects of three different cooling garments when used under a sealed, impermeable garment which simulated a space suit. The mean exercise metabolic rate while walking at 0.9 m/s (2 mph) was 464 +/- 33 W. An equilibrium condition was never reached during the uncooled suited control runs and the subjects lost a mean of 1.12 +/- 0.15 kg (2.5 +/- 0.3 lb)--approximately 2% of body weight--during exercise. The mean weight loss was 0.35 +/- 0.10 kg (0.8 +/- 0.2 lb) with an Apollo-type garment; 0.26 +/- 0.11 kg (0.57 +/- 0.24 lb) with the full-body cooling patch (garment 2); and 0.52 +/- 0.12 kg (1.15 +/- 0.26 lb) with the partial-coverage cooling patch (garment 3). Impedance plethysmography data showed an increase in leg blood flow when the working muscles were not cooled by liquid flow (garment 3), and the arm blood flow remained unchanged whether or not there was liquid cooling to the arms.