In order to study on the optimum quantity of exercise for children in their daily life, we first gave a physical exercise performance test to 109 infants from 5 to 6 years of age and selected from them two groups of children, one comprising two children (a boy and a girl) who scored highest in the aforesaid test and the other also comprising two children (a boy and a girls) who scored lowest in the same test. We then carried on the measurement of heart rates in those four children while observing the behaviour and motion of the children at the same time. The results we obtained are follows:
(1) Total heart beats per day of each of the four children ranged from 138109 beats (95.9/min.) to 161847 beats (112.5/min.) and the highest-scoring children showed the small-est number of heart beats and the lowest-scoring child the largest number.
(2) Each of the four subjects registered the least average heart rate (67.9-93.3 beats/ min.) and the smallest alteration of heart rate at sleeping time. The average heart rate increased from 112.1-121.4 beats/min. in their home life to 122.8-135.4 beats/min. in their kindergarten life.
(3) The highest showed less than the lowest on the total heart beats. But the highest showed the higher heart rate in the physical education and outdoor free activity time at kindergarten than the lowest. As a result of behaviour observation of children, we also found out that they would seem to take more interest in activities that involved removal playthings such as bicycle ridding, rope skipping and etc.
(4) During sleeping time that accounted for about 42% of a day, the heart rate alter-ation was the least, accordingly we propose that the average heart rate at sleeping time may be an index of the heart rate of awake time, but It should be reguired more physio-logical investigations at sleeping time in future.

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Ventilation threshold (VET), threshold of decompensated metabolic acidosis (TDMA) and lactate threshold (LT₁, LT₂) were investigated during incremental bicycle exercise for 20 boys (11.7±0.1 years) and 10 girls (11.2±0.2 years) .
Maximum oxygen uptake (VO₂max) was measured by treadmill running. There was significant difference between boys and girls in VO₂max per body weight, but no signif-icant difference per LBM. Mean values of each threshold (% peak VO₂) were as follows. VET was 53.3±2.2%, TDMA was 69.0±2.2%, LT₁was 51.8±2.2% and LT₂was 72.8±2.2%. These values were not higher than those of previous adult's data. There was no significant difference in lactate and ventilatory parameters between boys and girls, except LT₂and LT₄mM.
In conclusion, it seems that no difference is seen in lactate and ventilatory responses between 9-12 year boys and girls. VET and TDMA by bicycle exercise could be estimated by ventilatory responses in prepubertal children.

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Serum creatine kinase (CK) activity and myoglobin (Mb) level showed biphasic changes due to transient weight training. The first peak appeared within one day and the second peak appeared within several days after training.
We investigated the characteristics of each peak by measuring the total CK and CK isoenzymes (CK-MM, -MB, -BB) activities.
The results were as follows:
1) The first peak of Mb level appeared sooner than that of total CK activity. In two untrained subject, the second peak of total CK activity and Mb level were higher than the first peak.
2) The CK activity within four hours after training was that of CK-MM. CK-MB and -BB activities did not appear immediately after training, but they appeared within one day after training. CK-MB activity showed the highest value on the fifth day, and CK-BB activity was highest on the seventh day. Appearance of CK-BB activity was more apparent in the untrained than in the trained subjects.
3) The mean ratio of CK-MB activity to total CK activity was 5.3 % on the fifth day, and that of CK-BB activity was 2.9 % on the seventh day. These ratios were the highest among ratios in the post-training period.
It is suggested that the first peak represents a transient enzyme leakage into the blood stream, as the result of damaged muscles, especially in untrained subjects, while the second peak which appeared within several days after training represents, at least to some extent, the participation of ontogenetic muscle regeneration.

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The protein in urine from high-school male students before and after exercise was measured by TONEIN-TP method and ASPRO-GP method.
1. The total protein in urine was measured by using the TONEIN-TP method.
In comparison with before physical load, the total protein was increased after physical load.
2. Though ASPRO-GP method is used as the method that determine serum mucoprotein, this time it was made better as the method that determine minute amount of urinary mucoprotein immediately.
This method is more available, because it is able to determine more simply and rapidly.
3. The coefficient of correlation between the total protein concentration by the TONEIN-TP method and that add the albumin concentration to the acid soluble glycoprotein concentration by ASPRO-GP method was nice, and they were much almost the same.
Increase of urinary total protein after physical load is caused by increase of acid soluble glycoprotein and albumin.
4. From the above results, though TONEIN-TP methvd is effective to measure physical load after exercise, ASPRO-GP method is more effective to measure by increase of mucoprotein.

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Relationship between muscle fiber conduction velocity and muscle fiber composition was studied in vastus lateralis of well-trained athlete students, who differed considerably regarding their fiber type distribution with averaged 69.2% fast twitch (FT) muscle fibers for sprinters (12 male subjects) and 39.7% FT muscle fibers for distance runners (7 male subjects) . Measurement of muscle fiber conduction velocity during brief and maintained isometric contraction was made directly, using the zero-crossing time delay method between two surface myoelectric signals. Muscle fiber conduction velocities increased 4.40 to 4.84 m/sec for sprinters and 3.91 to 4.31 m/sec for distance runners as developing force increased from 25 to 100% maximum voluntary contraction (MVC) . The correlation coefficients between conduction velocity and % FT fibers were 0.59, 0.63, 0.64 and 0.84 for 25, 50, 75 and 100% MVC, respectively. During maintained at 50% of MVC conduction velocities in sprinters decreased linealy from 4.77 to 4.38 m/sec and in distance runners decreased from 4.11 to 3.96 m/sec at only last stage. It was suggested that the individual difference in conduction velocity was caused by different muscle fiber composition and that the changes of conduction velocity depended on the recruitment of muscle fibers.

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