It had been proposed by Kurata that the relative threshold value Fth of single motor units depends on gradient G (kg/sec) in the tension increase of muscle in such a manner as Fth (=T1⋅G) =ρ⋅ Gλ Here T1 is the time interval from the onset of E.M.G. to the moment of recruitment of a motor unit and ρ is the proportional constant. The motor unit with a positive/negative value of λ is characterized to be static/phasic. In order to confirm the above relation and to see whether or not the relation is also valid in the relaxation period, single motor units of M. VAST US MEDIALIS were studied by the same method as that of Kurata. The present findings are 1) At the contraction period the aove relation was confirmed. 2) At the relaxation period the above relation also holds, provided that Ftn and G are replaced by the tension at the moment of silence and the absolute value of G, respectively. The motor unit with a positive/negative value of λ is characterized to be phasic/static. 3) The value of Ftn and λ at the relaxation period are not the same as those at the contraction period.
In order to investigate the development of cooperatively responsing ability the subjects were made to carry out synchronous and altenate beating of colateral or contralateral hand and foot. 1. The synchronous beating of colateral hand and foot developed earlier than of contralateral hand and foot. In addition, hand-foot cooperative response developed to higher degree at the right side than at the left. 2. The hand-foot cooperative movement developed later in altenate beating with hand and foot than synchronous one. Development of altenate movement was earlier in the contralateral hand and foot than in the colateral and foot. Twenty percent of the adult subjects could not carry out altenate beating with colateral hand and foot. 3. A coefficient of variation in time intervals of beating was decreased with advanced age, but smaller in the synchronous movement than in the alternate one. The coefficient was the largest in the alternate movement of colateral hand and foot in little child. However, it was smaller in both synchronous and alienate movements in the subjects older than 13 years old. The above findings indicate that the beat movement differs in difficulty depending upon different combinations of hands and feet. This may be determined by the relationship between spinal reflex of four limbs and inhibition of it by the higher system. A movement which needs stronger inhibition and selection of a greater number of reflexes needs a longer time to be mastered. Children can not perform the most difficult colateral altenate movement untill the age of 14 or 15 years.
According to the past results of Sports Test, it was found that the night part-time high school students showed the significantly lower performance in endurance run than the full-time high school students. This fact may be partly due to the fatigue and the lack of motives necessarily caused by their mental and physical works in day time. This study was attempted to determine their aerobic work capacities (PWC170, Vo2max) in the same experimental condition as used for the full-time high school students and simulteneously comparing them with those of the full-time high school students in the same district. The subjects were 59 male and 38 female, aged from 15 to 19 years. The results obtained in this study were as follows 1) The mean values of PWC170 (kpm/min) for boys increased slightly with increasing ages till 18 years. But girls showed almost same values through the ages. The maximal value were 910kpm/min at the age of 18 years for the boys and 617kpm/min for the girls aged 16 years respectively. 2) For boys the mean values of PWC170 (kpm/kg/min) ranged from 14 to 15kpm/ kg/min and ranged from 10 to 11kpm/kg/min for girls. 3) As for the mean values of Vo2max (l/min) of the boys increased slightly untill the age of 18 years. But girls were same in values through all the ages. The maximal values were 2.71/min at the 18 years for boys and 1.81/min for girls aged 15 years respectively. 4) For boys the mean values of Vo2max (ml/kg/min) decreased slightly from 49.48 ml/kg/min with ages. The mean values of Vo2 max (ml/kg/min) ranged from 34 to 35 ml/kg/min for girls. 5) The night part-time high school students were lower than the full-time high school students in PWC170 (kpm/min), PWC170 (kpm/kg/min), Vo2max (l/min) and Vo2max (ml/kg/min) for boys. For girls no significant differences were in these valiables after the age of 16 years.
Influence of the all out exercise by the bicycle ergometer, all out exercise by the treadmill and the 5000 meter track running on the venous and urine concentrations of amino acid with healthy male and female subjects (include junior high school boys) were tested. The subject who was observed remarkable rise in his venous concentrations of amino acids was not always rose in his urine concentration of that. Generally, increasing ratio of serum alanine concentration was small and both the serum concntrations of essential and non-essential amino acids were reduced. On the several subjects increase of essential amino acids especially branched chain amino acids were observed. It seemed to us the sign of proteolysis according with the exercise. Quite a few difference of the effect on the serum amino acid concentrations among the individuals are observed.
The change in the venous concentration of amino acids in normal male and female adults was studied. After the brief fast (about 40 hours) except for a higher concentration of branched-chain amino acids in the plasma of female subjects, there was essentially no significant difference between the plasma composition of amino acids in female or male subjects. In only one male subject (Rohler's Index was 106), the transient fall of the branched-chain amino acid concentrations. Low caloric diet feedings resulted in a marked reductions of the plasma serine, glutamic acid, proline, glycine, arginine and threonine. On the other hand, high protein and high fat diet feedings resulted is a remarkable increasing of the branched-chain amino acid concentration and marked reduction of the plasma alanine concentration.