Foot Cooling To Preserve Physical Work Capacity During Occupational Heat Stress -a Pilot Study

PURPOSE: Rises in core temperature during occupational heat stress impair physical work capacity (PWC). Wearable cooling may help alleviate such impairments. Palm cooling attenuates rises in core temperature. Unfortunately, palm cooling may impact productivity given that most occupations require the use of hands. Using a similar physiological principle, this pilot study tested the hypothesis that plantar foot cooling attenuates reductions in PWC during simulated occupational heat stress. METHODS: In a randomized crossover design, eight healthy adults (2 women) completed two visits where they stood with their bare feet on either cooled (plate temperature: 14.2 ± 0.1 °C) or uncooled (plate temperature: 36.8 ± 0.1 °C) metal plates. In a 38.7 ± 0.4 °C and 48 ± 2% relative humidity environment, each visit involved 1 h of arm cycle ergometry (VO2: 0.5 ± 0.1 L/min; average workload in construction workers) followed by a 1 h PWC test. The PWC test required participants to freely adjust power output on an arm cycle ergometer to maintain a rating of perceived exertion (RPE) of ‘13’ (somewhat hard) (mean RPE: 13 ± 0), the average RPE observed in construction workers. Heart rate, rectal temperature, plantar foot temperatures, and power output were measured continually. Data are presented as mean ± SD. RESULTS: During the PWC test, average plantar foot temperature was lower in foot cooling (28.1 ± 0.3 °C) versus control (36.7 ± 0.1 °C, p < 0.001). Rectal temperature increased in both trials (main effect of time: p < 0.001), but the magnitude of increase did not differ between foot cooling (0.4 ± 0.1 °C) and control (0.3 ± 0.1 °C, p = 0.574). Heart rate increased (main effect of time: p < 0.001) in both foot cooling (average: 124 ± 6 bpm) and control (average: 120 ± 7 bpm) and did not differ between trials (p = 0.188). Power output did not change over time (main effect of time: p = 0.599) and did not differ between trials (p = 0.3840), with mean power output being not different between foot cooling (31 ± 9 W) and control (30 ± 9 W, p = 0.326). CONCLUSIONS: Cooling the glabrous skin of the plantar feet does not modify work output during a perception based PWC test during simulated occupational heat stress. Future work should determine the efficacy of foot cooling on PWC during more intense work and/or severe heat stress. Support: National Science Foundation (BCS-222626) National Science Foundation (BCS-222626)