岩永 光一

Seven healthy young male students participat-ed in this study. Each subject sat on a chair in an anteroom at 25℃ for 30 min and then entered a climatic chamber, controlled at 40℃ and R.H. 50%, and sat on a chair for 90 min. Cooling of frontal portion including the region around the eyes (FC),occipital portion (OC), and temporal portion (TC) began after 50 min of entering. An experiment without head cooling (NC) was also made for the control measurement. Thermal comfort and thermal sensation were improved by head cooling, but response was the same regardless of portion cooled. Although rectal temperature, mean skin temperature and heart rate showed no significant effect due to head cooling, forearm skin blood flow (FBF), sweat rate (SR), and body weight loss (ΔWt) had a tendency to be depressed. FBF in FC and TC decreased during head cooling, but that in OC and NC did not change significantly, while SR in FC was depressed.ΔWt showed total sweating to decrease by FC and TC, and FC to have greater inhibitory effect on sweating than OC. Thermal strain was evaluated by the modified Craig Index (I_s). I_s in FC decreased significantly more than in NC. Cooling of other portions of the head had no significant effect on I_s. Cooling of the frontal portion of the head may thus be concluded to have the most effect on thermoregulatory response in a hot environment.

The purpose of this study was to clarify characteristics of age-related changes in body shape in adolescence, in 11- to 19-year-old boys and girls, by using previously reported physique models of adult men and women as the scale. The scale consisted of four factors obtained by factor analysis using 30 items as variables, such as the values measured for the physique, skinfold thickness and body composition. The four factors were Factor 1: body fat, Factor 2: mass, Factor 3: Ieg length to height ratio, and Factor 4: Iength, and were interpreted in the men and women in a similar manner. The subjects were 307 boys and 368 girls; all were healthy. Thirty items were measured and included the values measured for the physique, skinfold thickness and body composition, as in the men and women. Factor scores in the subjects were standardized by mean and standard deviation for each item in the adult subjects, and calculated for individuals by using the coefficient of factor score in the adult subjects. The body shapes of the boys and girls were investigated from the factor score by age calculated for each factor. The following results were obtained: 1. Factor 1 tended to gradually decrease and reached the adult level at 15 years of age in the boys. But it tended to gradually increase and reached the adult level at 15 years of age in the girls; 2. Factor 2 rapidly increased with age in the first half of the teen years in the boys and girls, and it reached the adult level at 18 years of age in the girls, whereas this factor did not reach the adult level even at 19 years of age in the boys; 3. with regard to Factor 3, Ieg length tended to be temporarily somewhat long at 13-15 years of age in the boys, whereas the girls showed changes at approximate-ly the level of the adult subjects; 4. Factor 4 rapidly increased with age in the first half of the teen years in the boys and girls, and reached approximately the adult level at 17 and 15 years of age in the boys and girls, respectively. These results suggest that, the physique in adolescence is almost equivalent to that of adults and that body shape is essentially fully formed in the early 20s in boys and by about 18 years in girls through rapid growth in both mass and length during the first half of the teen years.

^31P-MRS spectra were obtained from human first dorsal interosseous muscle during and after the voluntary static abduction of the index finger. Endurance tasks were performed at randomly assigned contraction levels of 15, 20, 30 and 40% of maximal voluntary contraction (MVO. Muscle pH was calculated according to Taylor et al. (1983) using chemical shift between inorganic phosphate (Pi) and phosphocreatine (PCr) on the ³1P-MRS spectra. Mean values of endurance times of static contractions were 7.25, 5.33 and 3.08 minutes for 20, 30 and 40%MVC, respectively. At 15%MVC, all of the four subjects maintained contraction for 30 minutes, and the contractions were terminated at 30 minutes. Muscle pH at the onset of contractions were 7.12, 6.98, 7.01 and 7.08 for 15, 20, 30 and 40%MVC, respectively. At the end of contractions when the subject could not maintain the force level, muscle pH were 6.07, 5.97 and 5.94 for 20, 30 and 40%MVC, respectively. There was no significant difference in muscle pH at the end of contractions between three conditions by one-way ANOVA. In conclusion, there was a critical muscle pH of about 6.0 where static contractions could not be maintained