The purpose of this study was to clarify an improvement of awareness of the muscle tension as well as the performance during tension-control training by electromyographic (EMG) biofeedback. In order to relax the agonist (Biceps) and to contract the antagonist (Triceps) at elbow flexion, two experimental groups of eight undergraduate male subjects were provided with either no feedback (Condition NF) or the continuous visual feedback (Condition F) from each muscle activity. In Experiment 1, Condition NF was performed, and subsequently Condition F was run to prove the effect of muscle control. In Experiment 2, in order to test whether the training effect was retained or not, Condition F was first carried out, and its effect was compared with the later Condition NF. Additionally, immediately after each training trial in both experiments, the subject was required to guess whether the control level of both muscle tensions increased or decreased relative to the one of the immediately preceding trial in both experiments. The fol1owing results were obtained: 1) In the mean EMG recorded from Triceps, Condition F showed a significantly greater EMG than Condition NF in Experiment 1, while the significant difference in EMGs obtained from the two conditions was not found in Experiment 2. 2) In both experiments, the probability of correct guessings between adjacent trials in Condition F was significantly greater than that in Condition NF. 3) A significant difference in the probability of success in controlling the two muscle tensions was found between the two conditions in Experiment 1. 4) In Experiment 1, a significant interaction was found between overall subjective guessings and the actual muscle activities in Condition F, while, in Experiment 2, it was found in both conditions.
The purpose of this study was to analyze the process by which an innovative running program was disseminated through certain channels along time process among the runners. At the same time, it was also aimed to illustrate the applicability of the diffusion research method in sport situations. Data were collected from 2,616 persons who took part in the pop marathon race held in Fukui, Japan, by means of mailed questionnaires in the fall of 1983. Concerning innovativeness and opinion leadership of the pop marathoners, findings supported some of Rogers' generalizations as follows: 1) Earlier participants/adopters have a higher degree of opinion leadership than later participants/adopters. 2) Individuals tend to be linked to others who are close to them in participant/adopter categories. And, when interpersonal diffusion networds are heterophilous, followers seek opinion leaders who are more innovative. 3) Mass media channels are relatively more important than interpersonal channels for earlier participants/adopters than for later participants/adopters. 4) Later participants/adopters are more likely to discontinue running as a sport innovation than earlier participants/adopters. 5) Opinion leaders are more cosmopolite than their followers.
The purpose of the study was to compare the electromyographic characteristics between children and adults during isometric contractions. The subjects in this study were eight children (male, 5.8yr)and nine adults (male, 22.5yr). They were asked to exert respective brief isometric elbow flections at the strength of 20, 40, 60, 80% MVC, and then to sustain it at the strength of 60% MVC to exhaustion. The surface EMG was recorded from m. biceps brachii. EMG power spectrum, its median frequency and mean amplitude were computed from the recorded EMG. The results were as follows: 1. The median frequencies in children and adults varied little in accordance with the change of strength, the former being l0 to 14 Hz lower than the latter. The difference was significant at 20,40, 60% MVC (p<0.05) and 80% MVC (p<0.01). Amplitudes in adults were higher than those in children. The former showed exponential increment with the increase in strength in contrast to the latter which increased linearly and more gradually. 2. During sustained isometric contractions median frequencies in adults showed rapid linear decrement with time, but those in children decreased more slowly. In consequence, a significant difference in the median frequencies was observed at 80% (p<0.05) and l00% (p<0.01) of the duration in contraction. Amplitudes in adults were larger than those in children. The former increased gradually with time , but the latter showed no temporal change. 3. It seemed that the differences of EMG frequency and amplitude between children and adults during brief isometric contractions were caused by the difference in conduction velocity due to different muscle fiber diameters, and that the change in EMG during sustained isometric contraction was influenced by muscle lactate concentration and/or synchronization of motor units. It was concluded that the dominance in lower frequency components of EMG were evidenced in children during brief isometric contractions, and that EMG frequency components in adults lowered more rapidly with time than those in children during sustained isometric contraction.
To investigate the mechanism of the transformation of muscle fibre types during postnatal development, each of five litters of Wistar strain male albino rats were sacrificed at 3-12, 20 and 40weeks of age and examined histochemical properties of nerve cell and muscle fibre. The tibialis anterior, extensor digitorum longus, soleus, plantaris, and gastrocnemius muscles, and lumbosacral cord, identified by its root, were removed under ether anesthesia. Then serial frozen sections from these muscles were made and stained for ATPase and SDH (succinate dehydrogenase). The muscle fibres were classified into three types: FG (ATPase-rich and SDH-poor), FOG (both ATPase and SDH-rich), and SO (SDH-rich and ATPase-poor). Samples of the spinal cord were stained alternatively for PPL (phosphorylase) and SDH, and the anterior horn neurons were classified: αI (PPL-rich and SDH-poor), αII (both PPL and SDH-rich), and γ(SDH-rich and PPL-poor). The results were summarized as fol1ows: 1. A change in the histochemical properties during postnatal development was observed in the tibialis anterior, the soleus, and at deep regions of the gastrocnemius. However there was no change in the proportions of three fibre types in the extensor digitorum longus, the plantaris, and at middle, superficial regions of the gastrocnemius. 2. The ratio among the numbers of three types in the neurons showed no difference during postnatal development. In conclusion it may be said that the fibre types (muscle units) in the muscle are probably determined genetically (myogenic influence) until the motor coordination would be considered mature, but in the postnatal maturation process the proportions of the fibre types can be modified by the neurogenic influence to adapt for increased functional activity. Thus one and the same motoneuron not only determines directly the histochemical properties of its muscle fibres, but may also transfer fibre type to another .
The mechanical characteristics of a large-sized and a regular-sized racket were examined. The vibration of the rackets as one of the mechanical characteristics was measured and analysed by an impulse response method. The placement accuracy was investigated with the subjects of three different groups; beginers, intermediate players and trained players, and each hit 60 practice shots of a forehand drive and volley with these rackets at an appointed target. The results of this study were as follows; 1) The large-sized racket was 1.5 times larger in hitting area along the center axis than the regular-sized racket. 2) The large-sized racket showed a lesser and more moderate rate of variation in the rebound along the center axis of the racket face than the regular-sized. 3) The ball placement was nore accurate in forehand drive and volley with the large-sized racket than the regular-sized. 4) The bal1 flew farther in the forehand drive volley with the large-sized racket than the regular-sized. 5) The placement accuracy was worsen in the forehand drive and volley with both rackets as the ball speed increased.
Two experiments were conducted to investigate the response set characteristics and sex differences in immediate recall errors of isometric force information. The dependent variables were the percent constant error (PCE) which indicates the tendency to overshoot or undershoot the criterion force (response set), percent absolute error (PAE) which provides a measure of overall recall accuracy, and the relative difference limen (DL) which provides a measure of recall consistency. Subjects were 18 male and 18 female undergraduate students in experiment 1 and 14 ma1e undergraduate students in experiment 2. The criterion forces were 3 kg, 7 kg,1lkg, 15kg, 19kg and 23kg in experiment 1 and 7kg, 23kg and 27kg in experiment 2. The results are summarized as follows: 1) It was found that the DL dropped off markedly and significantly between 3 and 7kg, and that it became relatively constant at about 0.05 beyond 11kg. It was also found that the Sex difference was not significant with the DL. 2) The results of the PCE analyses showed that the males tended to overshoot all criterion forces (overshooting response set) in both experiments, while the PCE decreased as the criterion force increased. It was also found that the females showed smaller PCE than the male consistently, while the slope of PCE curve was very similar between the males and females, and that the females tended to undershoot the criterion force of 23kg (central tendency). 3) The results of the PAE analyses revealed that the females were significantly superior to the males on recall accuracy.
The purpose of this study was to determine the interrelati6nships among recordings in nine different running performances varying in distance from 50 m to 10 km, and the contribution of physique and physical fitness elements to each running performance. A total of 43 test items representing running ability (9 items), physique (7 items), and physical fitness (20 items) was examined on 167 healthy young boys aged 15 to 18 years. The major findings are summarized as follows: 1) The average running speed declined remarkably from 7.0 m/s in l00 m running to 3.7 m/s in 12 min running (x=2639 m) as the running distance increased, whereas the mean speed in distance running longer than 12 min running was almost constant. The mean speed in 12 min, 5 km, and l0 km running was approximately 50% of the mean speed of 50 m running. 2) The correlation coefficients of 50m running performance decreased remarkably from r=0.84with l00 m running performance to r=0.37 with 12 min running performance as the running distance increased. In contrast, the correlation coefficients of 10km running performance ranged from r=0.40with l00 m to r=0.90 with 12 min. 3) The contribution of physique to running performances seemed to be somewhat greater in distances shorter than 400m than in distances longer than 600 yards. Particularly, the contribution of body bulk to running performances was relatively large.. 4) The overall contribution of physical fitness elements to running performances in shorter distances (≦600 yeards) was relatively greater as compared with those in longer distances (≧800m). 5) The contribution of power to running performances decreased progressively up to 600 yards, while that of muscular endurance was almost constant throughout the range of distance. However, the relative contribution of muscular endurance among physical fitness elements seemed to increase progressively as the distance became longer. 6) Static strength and flexibility showed rather low relationships with running performance in distances shorter than 600 yards. Cardiorespiratory element related significantly with running performances longer than 400m, and the contribution of this element was relatively greater to running performances in longer distances (≧1500 m) than to those in shorter distances (≦800 m). 7) Agility, balance, and coordination were also found to contribute significantly to each running performance. However, the contribution of agility to each running performance seemed to decrease progressively up to 800m as the distance became longer.