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PHYSIOLOGICAL EFFECTS OF A COOLING GARMENT DURING INDUSTRIAL-TYPE WORK IN THE HEAT

Abstract

Cory L. Butts, Brendon P. McDermott, Cody R. Smith; University of Arkansas, Fayetteville, AR

Work in the heat elevates core temperature and increases physiological strain, more-so when wearing attire that limits convective and evaporative heat loss. Utilization of phase change cooling garments (CG) to attenuate the rise in core temperature may reduce physiological strain and protect against heat related illnesses. PURPOSE: To evaluate the physiological effects of using a phase change CG while conducting industrial-simulated work in the heat. METHODS: Twenty males (age 24.5±3.6 y, ht 1.79±8.04 m, body mass 75.0±10.7 kg, body fat 13.6±5.2%, body surface area 1.93±0.17m2) participated in two randomly assigned trials in an environmental chamber (34.2±0.05°C, 54.7±0.3% RH). Trials consisted of two 20 minute bouts of submaximal work (treadmill walking, lifting and moving 11.3 kg boxes, loosening and tightening nuts on bolts, carrying 3.6 kg dumbbells over steps) separated by five minute seated breaks. A final maximal effort performance bout (number of repetitions in 15 minutes of previous work without treadmill walking) was conducted, followed by a 10 minute recovery. Participant attire consisted of compression undergarments, coverall suit, gloves, and a hard-hat to mimic industry clothing. Phase change cooling inserts (10°C) were added to compression undergarment during the CG trial while control (CON) trial consisted of no inserts. Rectal temperature (Tre), heart rate (HR), and skin temperature (Tsk) were recorded pre and post submaximal work bouts, immediately post performance, and at three and 10 minutes of recovery. Physiological strain index (PSI) and heat storage were also calculated. RESULTS: Tre was different at baseline (CON 37.14±0.40°C, CG 36.99±0.48°C, P=0.03) and at 3 minutes (CON 38.78±0.38°C, CG 38.55±0.39°C, P=0.003) and 10 minutes (CON 38.72±0.37°C, CG 38.36±0.40°C, P<0.001) of recovery from performance. HR was lower in the CG trial (P<0.05) during mid-work bout 1, from pre-work bout 2 to post-work bout 2, and during performance and recovery (CON 133±12, CG 120±13 bpm, P<0.001). Tsk was reduced with CG from post-work bout 1 (CON 36.3±0.6°C, CG 31.8±1.0°C, P<0.001) through 10 minutes of recovery (CON 36.9±0.6°C, CG 32.9±1.2°C, P<0.001). PSI was greater during work-bout 2 in CON (4.54±1.77) than CG (3.30±1.49, P<0.001) trials. Heat storage was reduced with CG (27.04±7.56 W·m-2) compared to CON (42.69±9.90 W·m-2, P<0.001). CONCLUSION: By attenuating thermal strain during submaximal work in the heat, utilization of the CG reduced the physiological demand during performance and improved recovery. The reduction in heat storage during work in the heat may increase safety and reduce the risk of heat-related illnesses.

Funding provided by PreventaMed Inc.

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