In order to investigate certain characteristics of activity of motor units during strength control, discharges of single human motor units in the m. biceps brachii by use of electrodes inserted in the respective muscle were simultaneously recorded with tension developed at the elbow joint in its flexion effort. The results obtained were as follows :
1) When analyzed from the relationship between mean discharge interval of motor unit and its standard deviation, unit of other type which may be classified as “intermediate” (named “M”) unit than kinetic (K) and tonic (T) units as classified by previous workers was also found to be similar to that of leg muscles.
2) The tension produced by elbow flexion effort at the recruitment in a certain single motor units recorded in 15 seconds interval was also nearly constant during the 20 minute long experimental period which coincided with the result obtained in the case of leg muscles.
3) On the relationship between mean relative threshold of motor unit and its standard deviation, while the T unit was found to be of low threshold value, the K and M units, recording higher values than the case of T unit in most occasions, showed wider range in its values. After analyzing the relationship between the values of T and K/M units by use of a diagram, standard deviation of relative threshold was found to be larger in relation to its given mean value in the dominant arm than the recessive. No significant differences were found in the size of error in attempting to continue certain muscular tension with control between the dominant and recessive arms.
4) Statistically significant differences at 5% level confidence were found between different individual subjects in the frequency of single spike, appeared and recorded, ranging between 25.0-97.5 percent. The subject who showed higher single spike appearance frequency than the other was found to react significantly quickly in his single reaction time responding to photic stimulus (1% level) . Higher frequency of single unit spike appearance was observed in T unit than in K unit.

The pupils of both sexs who have been supposed luck of daily body movement and malnutrition were tested on their performance of exercise ability, physique and the assortment of food taken in a week. Results are as follows.
1) Whose showed above 160 on Rohler's Index is 2.2% of boys and is 2.7% of girls.
2) 24.4% of boys and 43.8% of girls are judged the obesity from the measurement of skinfold.
3) Side step, vertical jump, long distance run and backward flexibilty of those pupils are excellent than those of each national standard
4) The time of 50 meter run tend to faster than national mean value.
5) The broad jump distance, handball throw and forward flexibility are much the same with standard.
6) The grip strength, backward flexibility and step test score are inferior than the standard.
7) The general results of sports test of middle thickness skinfold group are superior than that of other thickness groups.
8) The results of sports test obtained on the group of much assortment of food eaten in a week is generally superior than that of poor group. The Rohler's Index and thickness of skinf old gained on the former is smaller than that of the latter.
On the above mentioned results we had discussed quite a few points and especially we would like to claim that the ideal healthy skinfold (upper arm+back) must be 20-25mm as boys and 25-35mm as girls of 12-14 years old.