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Abstract
The purpose of this study was to investigate the influences of menthol application according to the amount of surface area on physiological and psychological heat strains, along with body regional influences. Male students underwent two stages of experiments: [Experiment 1] Cutaneous thermal threshold test at rest on eight body regions with/without a 0.8% menthol application at T ^sub a^ 28°C and 50% RH; [Experiment 2] Six exercise tests with/without a 0.8% menthol spray at T ^sub a^ 28°C and 40% RH, while wearing firefighter's protective clothing (No menthol, PC^sub NO^; Face and neck menthol, PC^sub FN^; Upper body menthol, PC^sub UP^; Whole body menthol application, PC^sub WB^) or wearing normal clothing (No menthol, NC^sub NO^; Upper body menthol, NC^sub UP^). Experiment 1 showed that menthol caused no significant influence on cutaneous warm thresholds, while menthol applications evoked earlier detection of cool sensations, especially on the chest (P = 0.043). Experiment 2 revealed that NC^sub UP^, PC^sub UP^ and PC^sub WB^ caused lower mean skin temperature, especially with higher peripheral vasoconstrictions on the extremities at rest. During exercise, NC^sub UP^, PC^sub UP^ and PC^sub WB^ induced greater and earlier increases in rectal temperatures (T ^sub re^) and a delayed sweat response, but lessened psychological burdens (P < 0.05). Both physiological and psychological effects of PC^sub FN^ were insignificant. For a composite analysis, individual Menthol Sensitivity Index at cooling in Experiment 1 had significant relationships with the threshold for T ^sub re^ increase and changes in heart rate in NC^sub UP^ of Experiment 2 (P < 0.05). Our results indicate that menthol's topical influence is body region-dependent, as well as depending on the exposed body surface area.[PUBLICATION ABSTRACT]