In order to invesigate the changes in volitional muscular strength associated to the human growth, the five repetitive measures of maximal grip strength and the abilities of lifting the barbells in “curl” and “press” were examined.
1) Considerable differences associated to sex and age were observed in the decrement rate of the repeated grip strength. As the greatest rate of decrement was recorded for the ages from 14 to 23 years, it was considered that this decrement was due to the variation in the integrating mechanism of the contractile forces involving the nervous system or the fatigue of this mechanism, rather than the fatigue of the muscle itself.
2) The difference in ability of “press” between the two sexes became greater in accrodance with the advance in age. However, the improvement in the ability showed a linear increment both for the boys and girls, and there observed no particular stage in the course of development.
3) Up until age of 10 years, there was no difference in the ability of “curl”, which is associated to the sex, and the increment was linear. After the age of 11 years, the increment was accelerated both for the boys and girls. The ability in “curl” approached to that of “press” in boys, whereas, the ability in “curl” in the case of the girls exeeded that of “press.” The static muscular strength of the girls seemed to be considerably greater than the level assumed by the popular belief.
4) From the observations of the upper arm position in the “press” motion, the muscular development seemed to proceed from the trunk to the extremities. In this connection, the age around 8 or 9 years can be regarded as the period during which the muscular development is completed in some extent.
5) Among the boys younger than the age of 10 years, a great number of the boys failed to maintain their elbows at the right angle for a period of 5 seconds, after they “curl” the weight in the position. It was speculated that the balance between the “active” strength and the “passive” strength in muscles is established some time around the age of 10 years.

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A certain inhibitory effect upon the function of deep sensory mechanism of the muscle seems to be associated with the improvement of muscular strength resulted from an intensive training. At the basic weight around 1.0-3.5kg., a trained person shows : (1) a decrement in the ability of identifying different weights held in both hands ; and (2) a decrement in the ability of gradgin the half-way strength of the maximum grip strength. Even after the repeated five trials, these subjects could not approach the half-way strength in their self-grading muscular strength.
When the maximum exertion was repeated five times in the measures of grip strength or leg extension, the performance in the fifth trial is usually considerably worse than that in the first trial. This decrement rate varies considerably in accordance with the difference in the training method. As the mechanism of muscular exertion is habituated to labor, the decrement rate becomes smaller. In this measurement, the muscular ability in single maximum exertion is the concern ranther than the fatigue of the muscle.
The contact dimension of the foot to the ground decreases with the movement of the lower legs. By measuring this dimension, the amount of the milking action in the muscles may be estimated. There is no correlation between the amount of the milking action and the muscular strength in the static contraction.

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The data obtained from 106 7th grade boys and 224 8th grade boys were analyzed in terms of the inter-relationships among the results of various test items. The conclusions obtained from the analysis were summarized as follow :
1) No difference associated with the grade level was observed in the performances of side-step test, and chinning.
2) The group classified as heavy group in term of the body weight demonstrated a superior performances in dash shorter than 400 meters, whe reas the group classified as light-weight group did better in distance run of 1500 meters and 2000 meters.
3) The performances in distance-run longer than 1500 meters correlated higher with the performances in 100-meter dash rather than the scores of step test or the measures of lung capacity.
4) The negative correlation between the distance of broad jump and the time of 25-meter dash was higher in 8th grade boys than it was in 7th grade boys than it was in 7th grade boys.
5) For the 8th grade boys, the group 50-55 kg of body weight performed best in back strength and vertical jump, whereas the group 45-50 kg. body weight perfo-rmed best in chinning and elbow flexion strength. In these tests, the said two grou-ps ranked at the peak, and the performances decrease in both directions of larger and smaller body weight.

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Electrocardiographic studies were made on 676 excellent, well-trained atheletes.
The values of voltage and interval of each deflection were compared with normal value for the Japanese reported by Ueda et al. and were analysed statistically.
The results obtained were as follows:
1) R-R intervals were longer in atheletes than in untrained controls. Sinus bradycardia was markedly observed in atheletes in their twenties.
2) P-Q interval showed no difference between the atheletes and controls in a younger than twenty years group while that was more increased in the former than the latter in an older than 20 years group. Abnormal P-Q prolongation i. e. over 0.2 sec. was more frequent in excellent atheletes than non-excellent atheletes in a younger than 20 years group.
3) QTc (corrected QT, measured QT/√R-R) proved considerably large in atheletes especially those of a 15-19 year old group.
4) There was observed a trend of delay of the ventricular activation time (V. A. T.) in the right precordial lead, but no delay in the left precordial lead.
5) The duration of P-deflection showed a trend of enlargement in an older than 20 years group unlike in a younger group. The duration of P-deflection increased generally as age advanced. The same trend was also observed for P/PQ segment (Macruz' index) .
These findings might suggest the presence of left atrial enlargement, but they revealed neither left axis deviation in frontal plane nor mitral configuration of the P wave. They constituted a difficult problem explain.
6) R-deflection in the left precordial lead generally showed high voltage and especially in a younger group. In many of the atheletes studied SV₁ + RV₅ and RV₅ corresponded to Sokolow & Lyon's criteria for left ventricular hypertrophy (SV₁ + RV₅≥35mm, RV₅≥26mm), but those atheletes were without left axis deviation in frontal plane. In many of the atheletes R-deflection in the right precordial lead showed high voltage with a considerably correspondence to Sokolow & Lyon's criteria for right ventricular hypertrophy (R/S V₁>1. 0, RV₁≥7mm), and these atheletes revealed delayed V. A. T. in the right precordial lead.
The physiological right bundle branch block (Reindell) was also commonly observed, thus there was suggested the presence of right ventricular hypertrophy or overloading, but no right axis deviation was encountered.
It was assumed that a hard training might effect the right ventricle if not prod-uced a pathological ventricular hypertrophy
7) Atheletes in their twenties and thirties showed high voltage in T-deflection especially in V5, but they revealed almost the same T/R ratio as controls.
8) Abnormal ECG findings wree higher in an excellent group than a non-exce-llent group or an under-trained group.

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