Exercise heat acclimation causes human responses and safety performance improvements

Heat acclimation (HA) is a widely recognized physiological phenomenon of human body in hot environments. HA has many benefits, such aspreventing hyperthermia responses, and is an efficient way to improve human responses to hyperthermal environments. However, it is not known whether HA is dependent on the environmental conditions. Moreover, its mechanism and effect on the safety performance remain unexplored. In this study, we created a climate chamber to simulate a hyperthermal environment. Thirty healthy males were recruited for this study, who were then trained under the same ambient conditions (temperature of 38 °C and relative humidity (RH) of 40%). The training involved running on treadmills (at 5 km/h) to simulate heavy manual labor, and performing heat stress tests (HST) under six different conditions (32 °C/40% RH, 35 °C/40%, 38 °C/40%, 32 °C/70%, 35 °C/70%, and 38 °C/70%). Their physiological indices (rectal temperature, heart rate, sweat loss and skin temperature) and one psychological index (thermal sensation) were measured. Furthermore, a hazard avoidance test device (HATD) was designed to evaluate the individual safety performance by detecting human errors. The results show that training and environmental conditions have different effects on HA. After HA, the physiological and psychological strain were significantly improved. More importantly, HA also helped improve the participants' awareness of the dangers and required emergency responses to face potential hazards. Overall, a reasonable HA training under proper conditions is helpful to ensure the safety of human beings. More research is needed to study the role of HA on safety performance.