The following results were obtained by testing 2068 boys and girls in the eleme-ntary and junior high schools in Yaizu-shi, Shizuoka Prefecture :
1) The children of Yaizu-shi were shorter in stature and more endomorphic in build than the comparable group of Shuzenji district in Shizuoka. A slight retardation in the growth of their long bones was observed. Their measures of width-depth development and the muscular strength were inferior to those obtained from the other groups of same age level.
2) In the step test (height of the bench 35 cm, 30 steps per minute, for the duration of 3 minutes), boys ages from 6 to 13 years scored 65=70 with very small variation. In the same test, the girls scored similar to the boys, with the exceptions of ages 12 and 13 at which the scores dropped to 55 points. At age 14, the scores in the step test became high for the both sexes, reaching approximately 75 points. It seemed that the scores in the step test for the ages below 13 years are associate with the rate of work load to their leg muscles rather than with the cardio-vasular efficiency.
3) During the age period from 6 to 14 years, no variations associated with either sex or age were observed in the measure of lung capacity per an unit time. However, in the heart rate they are inferior to the adult standard.
4) The performances in vertical jump improved with the advancement of age for the boys. For the girls, however, very small improvement was registered after the age of 11 years.
5) The number of chinnings and the duration of hanging from the bar (with chinning position) improve with the advancement of age for the boys. For the girls, the duration of hanging time decreases after their age of 12 years.
6) The increment rate of the girls from age 6 to 14 years in the index “hanging time x weight” is approximately one-half of the boys' increment rate.
7) Tte increment rate of the girls from age 6 to 14 years in the index “vertical jump x weight” is approximately two-thirds of the boys' increment rate.
8) Thus the sex difference in motor ability becomes eminent after 13 years of age.
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