Validity of Perceived Skin Wettedness Mapping to Evaluate Heat Strain

The purpose of this study was to investigate the validity of a newly developed method for quantifying perceived skin wettedness (W (p)) as an index to evaluate heat strain. Eight male subjects underwent 12 experimental conditions: activities (rest and exercise) × clothing (Control, Tyvek and Vinyl condition) × air temperatures (25 and 32°C). To quantify the W (p), a full body map with 21 demarcated regions was presented to the subject. The results showed that (1) at rest in 25°C, W (p) finally reached 4.4, 8.3 and 51.6% of the whole body surface area for Control, Tyvek, and Vinyl conditions, respectively, while W (p) at rest in 32°C rose to 35.8, 61.4 and 89.8%; (2) W (p) has a distinguishable power to detect the most wetted and the first wetted regions. The most wetted body regions were the upper back, followed by the chest, front neck, and forehead. The first perceived regions in the skin wetted map were the chest, forehead, and upper back; (3) W (p) at rest showed a significant relationship with the calculated skin wettedness (w) (r = 0.645, p < 0.01) and (4) W (p) had a significant relationship with core temperature, skin temperature, heart rate, total sweat rate, thermal comfort, and humidity sensation (p < 0.05), but these relationships were dependent on the level of activities and clothing insulation. W (p) in hot environments was more valid as a heat strain index of workers wearing normal clothing in light works, rather than wearing impermeable protective clothing in strenuous works.