Evaluation of three commercial microclimate cooling systems.

Three commercially available microclimate cooling systems were evaluated for their ability to reduce heat stress in men exercising in a hot environment while wearing high insulative, low permeability clothing. Five male volunteers performed three 180-min experiments (three repeats of 10 min rest, 50 min walking at 440 watts) in an environment of 38 degrees C dry bulb (Tdb), 12 degrees C dew point (Tdp). The cooling systems were: 1) ILC Dover Model 19 Coolvest (ILC), mean inlet temperature 5.0 degrees C; 2) LSSI Coolhead (LSSI), mean inlet temperature 14.5 degrees C; and 3) Thermacor Cooling Vest (THERM), mean inlet temperature 28.3 degrees C. Endurance time (ET), heart rate (HR), rectal temperature (Tre), mean skin temperature (Tsk), sweating rate (SR), rated perceived exertion (RPE), and thermal sensation (TS) were measured. A computer model prediction of ET with no cooling was 101 min. ET was greater (p less than 0.01) with ILC (178 min) than THERM (131 min) which was greater (p less than 0.01) than LSSI (83 min). The subjects self terminated on all LSSI tests because of headaches. Statistical analyses were performed on data collected at 60 min to have values on all subjects. There were no differences in HR, Tre, SR, or TS values among the cooling vests. The subjects' Tsk was lower (p less than 0.05) for the LSSI than THERM; and RPE values were higher (p less than 0.05) for LSSI than the other two vests. These data suggest an improved physiological response to exercise heat stress with all three commercial systems with the greatest benefit in performance time provided by the ILC cooling system.