Kouhei Nakao

Kyushu University, Fukuoka-shi, Fukuoka-ken, Japan

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Publications (4)7.86 Total impact

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    ABSTRACT: To examine the effects of firefighters' self-contained breathing apparatus' (SCBA) weight and its harness design on the physiological and subjective responses, eight male students performed treadmill exercise under four conditions: the 8 kg firefighter protective clothing (PC) (Control), the PC + an 11 kg SCBA with an old harness (Test A), the PC + a 6.4 kg SCBA with an old harness (Test B) and the PC + a 6.4 kg SCBA with a new harness (Test C), at ambient temperatures (T(a)) of 22°C and 32°C. Besides highlighting the fact that a heavy SCBA had a significant effect on the oxygen consumption and metabolic rate, this experiment also found that in a T(a) of 32°C, in particular, the combined effect of 4.7 kg lighter SCBA and new harness design could reduce metabolic rate and improved subjective muscle fatigue and thermal discomfort. PRACTITIONER SUMMARY: An effort to alleviate the physiological and subjective burden of firefighters by reducing the weight of SCBA and by using the new harness design has provided satisfactory results in reduced oxygen consumption and in improved subjective responses in a hot air environment.
    Ergonomics 04/2012; 55(7):782-91. · 1.67 Impact Factor
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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 (a) 28°C and 50% RH; [Experiment 2] Six exercise tests with/without a 0.8% menthol spray at T (a) 28°C and 40% RH, while wearing firefighter's protective clothing (No menthol, PC(NO); Face and neck menthol, PC(FN); Upper body menthol, PC(UP); Whole body menthol application, PC(WB)) or wearing normal clothing (No menthol, NC(NO); Upper body menthol, NC(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(UP), PC(UP) and PC(WB) caused lower mean skin temperature, especially with higher peripheral vasoconstrictions on the extremities at rest. During exercise, NC(UP), PC(UP) and PC(WB) induced greater and earlier increases in rectal temperatures (T (re)) and a delayed sweat response, but lessened psychological burdens (P < 0.05). Both physiological and psychological effects of PC(FN) were insignificant. For a composite analysis, individual Menthol Sensitivity Index at cooling in Experiment 1 had significant relationships with the threshold for T (re) increase and changes in heart rate in NC(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.
    Arbeitsphysiologie 10/2011; 112(6):2171-83. · 2.66 Impact Factor
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    ABSTRACT: 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.
    Arbeitsphysiologie 03/2011; 111(10):2581-91. · 2.66 Impact Factor
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    ABSTRACT: The purpose of this study was to investigate the validity of infrared tympanic temperature (IR T(ty)) as a thermal index to evaluate the heat strain of workers in hot environments, in comparison with rectal temperatures at various depths (T(re-4, -8, and -16) for 4, 8 and 16 cm from the anal sphincter). Eight males underwent twelve experimental conditions: two activities (rest and exercise) × three clothing levels [Control, HDPE (high-density polyethylene coverall) and PVC (polyvinyl chloride coverall) condition] × two air temperatures (25 and 32℃ with 50%RH). The results showed that 1) in the conditions with most heat strain (HDPE or PVC condition at 32℃), IR T(ty) was equal to or even higher than T(re); 2) during exercise, physiological strain index (PSI) using IR T(ty) did not underestimate PSI-values using T(re-16), and overestimated those PSI-values from T(re-16) in HDPE and PVC conditions at 32℃; 3) during exercise, the relationships between IR T(ty) and heart and total sweat rate were stronger than those between T(re-16) and heart and total sweat rate. These results indicated that IR T(ty) is valid as a thermal index to evaluate the heat strain of workers wearing impermeable protective coveralls in hot environments. However, the application of IR T(ty) is limited only for strenuous works wearing encapsulated personal protective clothing with a hood in heat.
    Industrial Health 01/2011; 49(6):714-25. · 0.87 Impact Factor