We made the subjects take the exercise of six kinds from 5 to 90 seconds with maximum effort by Monark's bicycle ergometer. And we studied on anaerobic work by means of measuring the course of mechanical power, blood lactate, and oxygen debt. The results were as follows : 1) The mechanical power reached the maximum value from about 3 to 6 seconds after beginning the exercise regardless of the subjects and the work times, and then it decreased gradually with the passing of time. 2) The subjects who sent out the higher power in each work time within 60 seconds indicated the higher blood lactate and oxygen debt. 3) The relation between the oxygen debt per lean body mass and the blood lactate was found to be linear when the oxygen debt was less than about 110 ml, in other words, within about 60 seconds in the work time. But this relation became lower when the oxygen debt became over about 110 ml, or, the work time passed more than about 60 seconds. From these results we classified the work of maximum effort as follows: (1) the anaerobic work within about 6 seconds, (2) the work which contained a great deal of anaerobic factor from about 6 to 60 seconds, and (3) the work in which aerobic factor began to increase when the work time passed about 60 seconds.
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.
Skeletal muscle fiber of certain mammals consists of three types, namely, red muscle fiber, white muscle fiber and medium muscle fiber. The purpose of this study is to inquire histologically the effect of training upon medium muscle fibers by comparing with red and white muscle fibers. First, the form, size and distribution of red muscle fibers, white muscle fibers and medium muscle fibers of M. tibialis ant. of rats and mice were studied, and then the effect of training on those muscles was investigated. Wistar-strain rats and dd-strain mice were devided into training and control groups. One training group of Wistar-strain rats was made to run a treadmill with a speed of 40 m/min., a distance of 250 m and for a period of 90 days. Another training group of dd-strain mice was compelled to run on the treadmill with a speed of 20 m/min., a distance of 250 m and for a period of 60 days. After the training period, the anterior tibial muscle was removed and the histological method, using Sudan black B, was adopted in this experiment. The results obtained were as follows: 1) Form and size ; Red muscle fibers are more or less roundish, and white muscle fibers are polygonal. In gereral red muscle fibers are thinner than white muscle fibers. Medium muscle fibers are intermediate between the two in all respects. Red muscle fibers, white muscle fibers and medium muscle fibers are all thick at the peripheral part of the muscle, and become thinner towards the central part. 2) Number ; The ratio of number of medium muscle fibers involved in the anterior tibial muscles is less than that of red and white muscle fibers in rats and mice. 3) Distribution ; The outer layer of the peripheral region of the muscle is composed mostly white muscle fibers, and red muscle fibers are more abundant in the central part of the muscle and near the tibia. Medium muscle fibers reveal a gradual increase in the central part. 4) In rats, increasing rate of the entire cross sectional area of medium muscle fibers was 19.1%, that of red muscle fibers was 18.0%, and that of white muscle fibers was 33.0%. In mice, each value of medium, red and white muscle fibers was 13.4%, 10.6% and 31.5%. 5) The effect of training on the average cross sectional area per fiber showed the same tendency as the effect of training on the entire area of cross section in medium, red and white muscle fibers.
Theoretical principle of the indirect method for cardiac output determination by continuous gas-analysis of prolonged expiration was introduced and its practical utility and error sources were discussed. Merits and demerits of this method are as followd; 1) No blood sampling nor catheterzation is required. 2) Nonphysiological gas inhalation or injection of dye or other substances are not required. 3) Real time determination of cardiac output is possible when used with online computor processing. 4) Repeated measurement on the same subject is able to perform once every two minute at rest and once a minute during exercise. 5) Measurement during exercise is performed without any dificulty. 6) Several suppositions which used in this method may cause some error, especially anemia and unevenness of ventilation-perfusion ratio are possible two major error sources. Using a gas-spectometer, cardiac output of six subjects was measured by this principle at rest and during exercise of several intensities on a bicycle ergometer. Average values of cardiac output were 4.5, 7.5, 9.4, 12.3, and 14.1 1/min. at rest and during exercise of 150, 300, 450, and 600 kpm/min., respectively. From the results, utility of this method was practically confirmed for application to exercise physiology.