Efficacy Of A Potential Wearable Cooling Technology During Simulated Occupational Heat Stress - A Pilot Study

PURPOSE: Workers often work in the heat, which can impair physical and cognitive performance due to rises in core temperature. Wearable cooling technology may help alleviate such impairments. Cooling the glabrous skin of the hands attenuates the rise of core temperature during heat stress. Hand cooling may limit the functionality of the upper limbs, which are commonly required in manual labor. Cooling the glabrous skin of the feet may be an alternative method of body cooling, but the efficacy is unknown. Therefore, the purpose of this pilot study was to test the hypothesis that foot cooling during simulated occupational heat stress attenuates the rise in core temperature. METHODS: In a randomized crossover design, nine healthy adults (3 women) completed two experimental visits involving 1 h of arm cycle ergometry eliciting an oxygen uptake (VO2) of 0.5 ± 0.1 L/min in a 38.7 ± 0.8 °C and 47 ± 5% relative humidity environment. This VO2 is typical of the average workload in construction workers. The environmental conditions are often encountered in the southeast U.S. In one trial, participants stood with their bare feet on cooled metal plates (plate temperature: 14.1 ± 1.1 °C). In the other trial, participants stood on uncooled plates (plate temperature: 36.7 ± 0.2 °C). Heart rate, rectal temperature, and plantar foot temperatures were measured continually. RESULTS: Average plantar foot temperature was lower in foot cooling (30.1 ± 0.4 °C) versus control (36.5 ± 0.2 °C, p < 0.001). Rectal temperature increased in both trials (main effect of time: p = 0.015) and did not change differently between trials (trial x time: p = 0.253). The magnitude of increase in core temperature did not differ between foot cooling (0.2 ± 0.2 °C) and control (0.2 ± 0.2 °C, Cohen’s dz: 0.19, p = 0.590). Heart rate increased in both trials (main effect of time: p < 0.001) and did not change differently between trials (trial x time: p = 0.302). The magnitude of increase in heart rate did not differ between the foot cooling (12 ± 10 bpm) and control (15 ± 12 bpm, dz: 0.42, p = 0.278). CONCLUSIONS: Cooling the glabrous skin of the plantar feet does not attenuate the rise in core temperature during simulated occupational heat stress. Future work should determine the efficacy of foot cooling during more severe heat stress. Support: National Science Foundation (BCS-222626) National Science Foundation (BCS-222626)