Some factors influencing the tension development of human muscles at the maximal exertion was analyzed in order to find out some desirable indicators of the characteristics of the voluntary exertion of muscle force.
1) The isometric tension development of the maximal exertion of hand-gripping and arm-bending was recorded simultaneously with the measurement of electromyogram, respiratory curve, electrocardiogram and reaction time. The subjects were all male and 22 to 61 years old.
2) The length of time needed to exert muscle force from 20 to 80% of each recorded maximal force exerted maximally was nearly constant so far as the interval and number of repetition was less than 5 sec and 30 respectively. The correlation coefficient between the standard deviation of the undulating descending curve of the decrease in maximal muscle force during repetition described above and that of this length of time from 20 to 80% definded here was +0.64.
3) The values of tan θ and tan ψ calculated from the (P_max-P) -log t relation were in some cases found to decrease during repetitive exertion under the same conditions as mentioned above, but the decrease was in most cases not so remarkable. The values of tan θ and tan ψ ranged from 0.1 to 0.2 (kg/msec) and from 0.3 to 0.5 (kg) respectively.
4) The maximal force of hand gripping was measured immediately after a conditioning exertion of force of various intensity (i.e.25, 50 and 75% of the maximal force of hand gripping exerted maximally by each subject prior to the measurement) . The tan ψ and tan θ were maximal when no conditioning was loaded, and they decreased with increasing intensity of conditioning exertion.
5) The tan θ of the test exertion of hand gripping exerted maximally was larger when a very short time of pause was interposed between the conditioning and the test exertion than that without conditioning exertion at all.
6) Both tan ψ and tan θ were larger when the condition exertion was done by antagonistic muscle of hand gripping than without conditioning exertion at all.
7) The maximal force of flexion of the one arm was not influenced by the simultaneous maximal exertion of flexion of the other arm.
8) When a constant time interval (i.e. 0.5, 1.0 and 2.0 sec) was interposed between the time of beginning of the maintained maximal exertion of the one arm and that of the other arm, the decrease in the tension of the maximal flexion of the first arm due to the maximal flexion of the second arm was larger than that due to the maximal extension of the second arm. This decrease in tension was larger when the first arm was the left one than that when the first arm was the right one. This decrease in tension was also larger when the length of the time interval mentioned above was arbitrarily chosen by the subject than that when the time interval was prescribed.
On the basis of the results mentioned above, the characteristics of the voluntary exertion of muscle force was discussed.

Well-trained Kendo and Judo Champion (10 members respectively) were participated at the physical fitness test program including body height, body weight chest girth, length of arms, length of forearms, girth of upper arms, girth of forearms, girth of thighs, girth of lower legs, back strength, grip strength, vertical jump, side step test, foward flexibility and modified Schwab's test
Results were as follows.
1) Significant difference between body height, length of arms, length of forearms, back strength, grip strength, vertical jump, side step test and forward flexibility of Kendo and Judo Champions were not found.
2) Significant difference between body weight, chest girth, girth of upper arms, girth of forearms, girth of thighs, and girth of lower legs of Kendo and Judo champion were observed.
3) Difference between right and left of limbs of Judo champions were not recognized, although on Kendo champion size of girth of right and left thigh and lower legs were not changed, nevertheless the girth of right both upper arms and forearms were bigger than those of left, the difference of total surface area of arms obtained with modified Schwab's method was not found between the right and left arm.
From above-mentioned facts, I had discussed on the training effects of Kendo performance and on the judgment of its effect.

1290 townswomen aged from 4 to 76 participated in this experiment. All of them were measured on body height, body weight, skinfold (abdomen, back, upperarm) jumping reaction time, grip strength (right and left) timed vital capacity and forward flexibility. Some of them were measured on girth of upper arm, forearm, wrist, lower leg and ankle, chest girth, sitting height, backward flexibility and vertical jump beside above mentioned items.
Results were as follows.
1) Skinfold was increased with age. The highest degree of increase was obtained on abdomen, next on back, lowest on upper arm.
2) After 20 years old, ability of vertical jump was clearly reduced with age, but jumping reaction times were not so decreased.
3) Maximum vital capacity and timed (one second) vital capacity were decreased mark-edly, but ratio of one second V. C. and chest girth were not change after 20 years old.
4) After 20 years old no change was found on the girth of forearm but the grip strengthes were reduced strikingly.
5) Correlation between jumping reaction time and Rohrels's Index were not observed.
6) On the forward flexibility no change was found with age. No correlation between forward flexibility and skinfold was obtained.
7) After 20 years old backward flexibility was reduced with age, but among same age group the correlation between skinfold and backward flexibility was observed.
8) Highest value of body density, fat free mass weight (FFM) and FFM/height body×100 of were obtained in ages from 15 to 17, and after these ages they were reduced with age.

Inhabitant of Tokyo aged above from 20 to 75 years were tested. Many items concerning with exercise ability, performance, physical fitness and physique were measured. Results were as follows.
1) For male, with advancing of age, the forward flexibility was reduced remarkably and backward flexibility tended to be reduced. But the decline of grip strength and vertical jump was a little, jumping reaction time and side step test didn't change. The time of rapid walking of 1500 meter was shortened by ageing. Vital capacity and Zigzag dribble became worse. Systoric blood pressure was high in their twenties.
2) For female, with ageing backward flexibility was reduced remarkably, vertical jump and rapid walking of 1000 meter were reduced slightly. Forward flexibility, grip strength index, jumping reaction time didn't vary. Side step test and zig-zag dribble became worse. The change of vital copacity wasn't found. Increasing tendency of blood pressure wasn't so remarkable.
3) In man, increase of skinfold-thickness was found on abdomen but a little on both upperarm and back with ageing.
4) In woman increase of skinfold thickness was found on both abdomen and back. but a little on upper arm. Up to 40 years the thickness of upper arm skinfold was thicker than that of back, but afterword 40 years it was reversed.
5) The correlation between vertical jump and skinfold thickness wasn't found in middle aged men and women.
6) The measurment values of mean grip strength, wrist girth and skinfold (back + upper arm) were divided in three groups according to their size. Each individuals were classified in three size division of three items. All of the permutations and combinations of those 27 parties were exist. But the frequency of each parties was not equal. The difference among these frequencies were biger in men than in women, in up to 40 years group than in above 40 years group.
7) The correlation between Rohler's Index and abdomen skinfold thickness was not shown.

The pressure exerted by the index finger tip was continuously recorded while the human subject was trying to maintain the pressure at the level of a given pressure (this pressure is named ‘target pressure’, 0.5-500g) with optical information for ten minutes, and the results obtained under various conditions were analysed.
1) The errors tended to be minimal in the range between 40 and 50g target pressure, and increased approximately in proportion to the target pressure above 50g.
2) When the subject relaxed his index finger, the errors decreased with decreasing target pressure in the range of less than 50g.
3) The errors were increased by excluding optical information. In target pressure less than 50g, the increment of the errors due to a decrease in the skin pressure intensity was further increased by exclusion of optical information.
4) In small target pressures, the errors tended to decrease transiently in evening, while in large target pressures the errors showed a gradual increase from morning toward evening.
5) The errors showed generally minimal values 2 or 3 minutes after the beginning of the measurement, and thereafter increased more remarkably in large target pressures than small ones.

1) The reaction time of the avoidance movement of jumping off toward a given place, which was regarded as an indicator of the quickness of movement of the group of muscles of the lower limbs, was measured and compared with the quickness of these of the upper limbs.
2) The reaction time of movement of placing one's hand from one to the other of the two pushing-plates, by pushing which the electric circuits were closed, was measured. The reaction time of the commencement of the movement was similar to the simple reaction time, and its correlation with age was not high. The time taken to place one's hand on the other plate tended to be a little longer with subject of middle and high ages.
3) The dispersion of the values of reaction time of both the commencement and the termination of movement when measured repeatedly was similar to that of the simple reaction time, but the dispersion of the difference between these two kinds of reaction times, that is, that of the time taken to move one's hand was smaller than that of the simple reaction time.
4) Concerning one-step jumping aside to the right hand side, the reaction time of the commencement of movement under the condition that the legs were moved one by one was longer than the simple reaction time, and was also longer than that of the simultaneous movement of the both legs. The reaction time of both the commencement and the termination of movement was longer with higher ages, and was longer with women than with men. This relation was more evident in the successive movement of each legs than in the simultaneous one. The frequency distribution curve obtaind by repeating the measurement of the reaction time of jumping off showed a nearly normal distribution curve. The correlation between the reaction time of hand movement and that of jumping off was not so high.
5) The scattering of the landing position of one-step jumping aside to the right hand side did not show any correlation with the values of the time taken to move one's legs.There was, however, a high correlation (r=+0.96) between the scattering of the landing position and that of the reaction time.
6) There was no large difference between the reaction time of one-step jumping aside to the right hand side and that to the left hand side. With respect to forward jumping, the period of time during which the pressure at the first pushing-plate remained equal to the body weight was longer when the both legs were not simultaneously moved. There was no large difference between forward and backward jumping.
7) The variation of the reaction time of two-steps jumping with respect to age was similar to that of one-step jumping.
8) The results mentioned above indicate that one-step jumping aside is to be adopted as an indicator of the quickness of movement of the group of muscles of the lower limbs, and that it is practically useful to measure the time taken for one's one leg to tread on the second pushing-plate.

1) The time course of nearly isometrical tension development of human voluntary muscular contraction was analyzed for the purpose of finding some desirable indicators of the capability of human body to exert maximal muscle force as fast as possible.
2) The isometric tension curves of maximal exertion of hand gripping, arm and indexfinger bending recorded, the linear relation between P_max-P, which is a difference between its maximal tension and each value of tension in the time course, and log t, which is the logarithm of time corresponding to each value of tension, was found in each of three portions of a whole curve of time course of tension, the three portions being a range from P₀ (log t₀) to P₁ (log t₁), from P1 (log t₁) to P₂ (log t₂) and from P₂ (log t₂) to P_max (log t_max.) respectively.
3) The range from P₁ (log t₁) to P₂ (log t₂) is a phase in which the tension increases most rapidly from an initial small tension to a large tension and is, therefore, regarded as a most characteristic one with respect to the time course of muscle force development exerted voluntarily as fast as possible.
4) The angles of intersection of the line connecting P₁ (t₁) with P₂ (t₂) or P₁ (log t₁) with P₂ (log t₂), with the abscissa in the tension-time or tension-log t curve, which are denoted as or respectively, were found to be able to be adopted as indicators of the capability of human body to exert maximal muscular force for a short period of time.
5) The tension curves were found to be nearly the same each other when they were recorded three or four times in the interval of 30 seconds with one and the same subject. If the difference is small between the first and the second record of the time course of a given subject, either of them may be adopted, but if not so, one have to only record the third curve and adopt either of the two resembling each other among the three records.
6) Concerning the subjects of the same age, the difference between P_max and P₂ was small and the tan was large with a subject whose P was large. The tan ψ or tanθ was as a rule smaller with subjects of middle and high ages than with younger ones.
7) The Pmax decreased with lapse of time when the maximal effort of contraction whose duration was one second was repeated in the interval of three seconds for two minutes. Under this condition the tan ψ increased in some cases, but did not in other cases. Also there were some cases in which t₁ remained constant in spite of a decrease in the P_max with subjects of middle and high ages, P₁ of them decreased with decreasing t₁. In short the change of the characteristics of the tension curves due to fatigue showed some individual variation.
8) The decrease in the P_max during a continuation of maximal effort of contraction was more remarkable than in the case of repeated contraction mentioned above, but the changes of the values of indicators were nearly the same in both cases.
9) The P_max of hand gripping and index-finger bending decreased to some extent when examined immediately after the effort of contraction had been continued under the condition that the blood stream in the fore-arm was stopped by applying the maximal blood pressure by a manchette of sphygnomanometer. The change of the values of the indicators under this condition was nearly the same as under the condition without the application of pressure, but under the former condition there were some cases in which a portion of the tension curve corresponding to P₁ (log t₁) deviated from the intersection of the lines, or some cases in which the records of one