title: Thermoregulatory responses of prepubertal boys and young men in changing temperature linearly from 28 to 15 degrees C.
abstract: To examine thermoregulatory responses of prepubertal children to cold stress, 11 boys (aged 8 years) and 11 young men (aged 19-23 years), wearing only trunks, participated in this study. They sat in air at 28 degrees C for 30 min (equilibrium period) and then in conditions where air temperature (Ta) was decreased linearly from 28 to 15 degrees C (at a constant rate of 0.22 degrees C.min-1) for 60 min, at a fixed relative humidity of 65%. In the equilibrium period there was no significant difference between the groups for rectal temperature [Tre, mean 37.30 (SEM 0.10) and mean 37.43 (SEM 0.14) degree C in the boys and the men, respectively] or for the respective skin temperatures (except for the forehead), but metabolic heat production (M) was significantly greater for the boys [mean 57.1 (SEM 1.2) and mean 52.0 (SEM 0.9) W.m-2, P < 0.005]. With declining Ta, the skin temperatures decreased in both groups (P < 0.001), but the decrease was significantly greater for the boys (P < 0.05), especially on the limbs as represented by the thigh and forearm. No significant correlations were observed between the limb skin temperatures compared to surface area-to-mass ratio or limb skinfold thicknesses in either group. The rate of increase in M as Ta decreased was significantly lower for the boys (P < 0.01) largely because of a higher M before the cold exposure. Thus, the mean M during the cold exposure did not differ between the groups [mean 63.6 (SEM 1.1) and mean 61.6 (SEM 1.1) W.m-2 in boys and men, respectively]. When the Ta was lowered, Tre in the boys started falling (P < 0.001), whereas the Tre in the young men did not change for 60 min. The Tre during the 60-min exposure was significantly lower (P < 0.001) for the boys [mean 37.01 (SEM 0.13) and mean 37.48 (SEM 0.18) degree C at the end of the exposure]. It was concluded that when Ta was lowered, the prepubertal boys appeared to vasoconstrict more in their limbs and to be somewhat more hypothermic, compared to the young men.
authors.affiliation: Department of Hygiene, Kobe University School of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
authors.forename: T
authors.initials: T
authors.lastname: Araki
authors.forename: J
authors.initials: J
authors.lastname: Tsujita
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002648:Child; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008660:Metabolism / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D011627:Puberty / Q000502:physiology*; D012881:Skin Temperature / Q000502:physiology; D012885:Skinfold Thickness; D013696:Temperature; D013997:Time Factors