An electromyographic silent period preceding to a synchronous discharge in a rapid voluntary movement was investigated from the viewpoint of a motor control. While subject stood and held his knees bended stationary against the gravity, he was asked to respond to a signal with a rapid vertical jump as quickly as possible. During the preparation to the movement, motor units activity, which was detected with use of semi-microelectrodes, revealed itself monotonically, and this activity was identified as motor volley from “continuously long interval firing motor units” from analysis of the discharge frequency as described by Grimby and Hannerz. Hence the resulting silence must be due to disappearance of the tonic motor volleys under the conditions of these experiments. The problem of how this adjustment is brought about was speculated as follows. It can be assumed that the central nervous system switches from tonic to phasic excitation related with a rapid change from tonic to phasic voluntary contraction of muscle. As to the occurrence of the silence, the muscle electrical activity for static contraction must cease earlier than onset of the phasic motor volleys. EMG premotion silent periods, those began not coincidentally in a movement were observed among different muscles. They appeared, in many cases, orderly dependent on the onset of the synchronized muscle electrical activity. However, the silent periods without any order were recorded in a movement. Furthermore, it was confirmed that this silent period can occur in a limited muscle or its part in a movement. These results led to an assumption that the silences with the orderly onset of the synchronized EMG appeared in better-coordinated movement than the movement with the silent period without such order and with the silence in a limited muscle or its part. Even more interesting is the assumption that well trained subject can excite tonic and phasic motor units separately and switch their excitation more agilly, because the premotion silent period was observed frequently in trained subjects.
In order to find out what changes would happen to the cancelling in the course of the program and what differences would be caused in the cancelling ability depending on the degree of program formation, we examined the changes of adults (in their 20s and 50s) and children, and obtained the following results. 1. In the cases of cancelling actions halfway, delays in the reaction time and movement time of both the adults and children were found, unlike the cases of controlling actions. This tendency was noted remarcably in the adults at their age of 20s and in the children. 2. The time for the switching into the next actions by cancelling the previous actions was found to be the longest at the initial stage when the action program was intiated. 3. The fluctuation in the movement times immediately after initiating actions was extremely small in both controlling and cancelling actions. However, as the actions advanced, the values of the cancelling actions showed larger fluctuations. This trend could be noted very significantly in both the adults at the age of their 20s and the children. 4. The time of delays by more than 20 over the mean value in both the time for reaction and the time for movements were noted more frequently in the cancelling actions especially in the latter half of the actions where the actions advanced. 5. The emergence of erroneous action (miss-touch) for cancelling to stop the actions and to push the next key instead was the most frequent when the cancelling was made at the initial stage of the action, and the rate of miss-touch was invariably approx. 50% at any age. As the actions advanced, the frequency of miss-touch decreased. On the basis of the above findings, it can be concluded that the earlier it is in the course of proceeding with the program, the more it is difficult to cancel the program in the central nerve system for cancelling the on-going action, and that, as the program advaces, it is easier to cancel the program. It was furthermore demonstrated that, as the age advanced, the program could be formed more firmly, making it difficalt to cancel the program.
Human systolic blood pressure and heart rate were measured continuously. This was accomplished by an indirect noninvasive method employed while the subject was involved in exercise. The characteristics of the measurements, and the factors which produced those characteristics were investigated. Then, an index L composed of all of the significant factors was sat up in order to compute L-Scores. L-Score was later statistically considered as a significant indicator of evaluation of a subject's training level. On the other hand, BP-HR Scores of each subject were obtained from BP-HR Scoring Chart. The Scoring Chart was drawn in order to serve as a scoring table for estimating subjects' training levels according to a formula which represented the characteristics of increments above resting blood pressure and heart rate. Highly significant correlation between L-Scores and BP-HR Scores, 0.94 at P<0.01, was observed. The study concluded that synthetic investigations of multi factors such as computing L-Scores were more efficient than a singular investigation of individual factors in order to examine a human cardiovascular function from measurements of blood pressure and heart rate during exercise. For simplification of the measurements and computations, application of BP-HR Scores was considered as an effective method.
On 1146 factory workers from age 17 to 59 (661 males and 485 females), the simple reaction time was measured on the right hand, and in addition, the jumping reaction time (reactiom time, movement time and total time) by an auditory stimulus was measured using a specifically designed equipment. The results were as follows: 1. The simple reaction time and the jumping reaction time were generally longer in older age groups on both male and female. The prolongations of the total jumping reaction time and the movement time of the jumping reaction with age were almost in parallel with ageing, but in the simple reaction time and the reaction time of the jumping reaction, the prolongation with age was greater after 50 years old on male and after 40 years old on female. 2. The jumping reaction time was shorter in male than in female. But the simple reaction time was shorter in female than in male contrary to the previous reports. The short simple reaction time in female found in this study may be due to the training effect through their daily task. It was also observed that the individual variations of the simple reaction time and the jumping reaction time were greater in female's than in male's. 3. Most partial correlation coefficients freed from age effect calculated between each reaction time and measure of body build and physical fitness were generally small in every age groups for both male and female. 4. The correlation coefficient between the simple reaction time and the jumping reaction time, and the correlation coefficient between the reaction time and the movement time of the jumping reaction were relatively small for every age groups both male and female. These findings are suggesting that the simple reaction time measured on hand is not a good index for the evaluation of one's agility, and that the separate observation of the reaction time and the movement time in the jumping reaction time may be useful for the parfect evaluation of one's agility through the test of jumping reaction.
Measurements of muscle and tendon blood flow by hydrogen gas clearance method were performed on M. tibialis anterior, M. gastrocnemius and M. soleus of the rabbit anesthetized with urethane. A wire type of Pt-Pt black electorode with 80μm in diameter was applied as the hydrogen gas sensor. With spontaneous arterial mean pressure at 84.6 mmHg, the resting blood flow (ml/min/100g) (mean±S.E.) (n) in muscle and tendon were 21.33±1.79 (14) and 26.60±3.96 (12) in tibialis ant., 14.46±1.95 (21) and 30.49±3.96 (12) in gastrocnemius and 12.53±1.79 (19) and 29.83±6.33 (8) in soleus, respectively. After exercise elicited by sciatic nerve stimulation at 1 to 5 Hz, muscle blood flow increased approximately two times above the control whereas the tendon flow showed no change or a slight decrease in some data. For the observation of the time course of blood flow, tissue temperature was measured by a needle type thermocouple. Muscle temperature increased immediately after the onset of exercise, but the same phenomenon was not observed in tendon tissue. These results indicate that the blood flow of tendon is larger than that of muscle at rest, and during exercise biomechanical tension force may affect on the regulation of tendon circulation.