| Keywords |
Heat strain; Hot-humid environment; Military ergonomics; Protective clothing; Tracked vehicle crew |
| Abstract |
This study evaluated the thermal strain while wearing the Republic of Korea Army flame-resistant tracked vehicle crew uniform (Tracked), compared with a standard combat uniform (Control), under thermoneutral (25°C, 50%RH) and hot-humid (34°C, 60%RH) environments. Eight young males participated in four experimental conditions (25C-Control, 25C-Tracked, 34C-Control, and 34C-Tracked), each consisting of a 10-min rest, 30 min of repeated ammunition carriage, 20-min arm ergometer exercise, and a 10-min recovery. Compared with the thermoneutral environment, exposure to a hot-humid environment significantly increased mean skin temper- ature, clothing microclimate humidity, heart rate, physiological strain index, total sweat rate, thermal sensation, thermal discomfort, humidity sensation, and perceived exertion (all Ps < 0.05). Rectal temperature did not differ among conditions. Gastrointestinal temperature was significantly higher in 34C-Tracked than in 25C-Tracked during the arm exercise and recovery periods (P < 0.05), whereas no significant difference was found between Tracked and Control within the same environment. The only clothing-related difference was observed in thermal comfort, where 34C-Tracked was rated significantly more uncomfortable than 34C-Control at rest (P < 0.05). Clothing microclimate humidity exceeded 90%RH under the hot-humid condition, indicating restricted evaporative heat loss. In summary, compared with the combat uniform, the tracked vehicle crew uniform induced greater physiological strain, reflected by higher gastrointestinal temperature and subjective responses, under the hot-humid condition compared to the thermoneutral condition, however, the strain remained below a hazardous level. |