Boys and girls of elementary school (1 st, 3 rd and 6 th-grades), junior high school (2 nd-grade) and senior high school (2 nd-grade) were tested for 2 days to examine the reliability of grip strength, back strength, arm strength and leg strength.
The following results were obtained:
1. When elementary school boys performed three trials of these four items, over half boys recorded maximal value up to the second trial.
2. The reliability of tests applied to the left and right sides (grip strength, arm strength and leg strength) was not different each other.
3. In boys and girls attending elementary, junior- and senior high schools the reliability of grip strength was highest and the next was back strength.
4. Grip strength had statistically significant relationship to the other three items. Thus grip strength is considered to be the representative of four strength tests for growing boys and girls.

We investigated the relationship between maximum oxygen uptake and the amount of lipid peroxide in serum before and after exhaustive exercise. The levels of serum lipid peroxides observed in a group of 6 males with high oxygen uptake were significantly lower than those of the low oxygen uptake control group (4 males) before and 0, 30 and 60 minutes after exercise. The amount of serum lipid peroxides increased slightly in each group after exercise. However, that amount decreased more quickly in the group with high oxygen uptake than the control group. Catalase and superoxide dismutase activities in erythrocytes showed no significant differences between both groups, nor between before and after exhaustive exercise.