Analysis of "Teno-uchi" maneuver in releasing Japanese-style bows based on muscle activities and forces acting on the bow.

Since a Japanese-style bow has a very complicated shape and structure, an archer has to apply the "Teno-uchi" maneuver including horizontally twisting torque, or "Nejiri", and sagittally down-pushing torque, or "Uwa-oshi", to the restoring bow in order to hit the target. The purpose of this study was to investigate the biomechanical relationship between the muscular activities of the left forearm and the operation of "Teno-uchi" maneuver. Surface EMG of left forearm muscles and the two kinds of torque acting on the bow around the time of release were recorded in 10 experienced subjects during arrow shooting. The "Biku", an involuntary resignation from release happening in the shooting, was also examined. Close analyses of the results revealed that activation of the extensor carpi ulnaris and extensor digitorum muscles together with inhibition of the flexor carpi ulnaris muscle brought about "Nejiri", while activation of the extensor carpi ulnaris as well as flexor carpi ulnaris muscles and inhibition of the extensor carpi redialis longus and extensor digitorum muscles gave rise to "Uwa-oshi", thus causing activities of trade-off nature in the extensor digitorum and flexor carpi ulnaris muscles for the "Nejiri" and "Uwa-oshi. The trade-off activities were presumably actualized through time-sharing coordination between the muscles.

Age-related EMG variables during maximum voluntary contraction.

We studied the neuromuscular adaptation that occurs with aging by comparing changes in surface electromyography (EMG) variables from the tibialis anterior muscle in 12 young (21.4 +/- 1.7 yr. old) and 13 older subjects (70.8 +/- 3.1 yr. old). EMG variables such as the muscle fiber conduction velocity, median frequency, and averaged rectified value were calculated during maximum voluntary contraction for 5-sec. isometric contractions. The dorsiflexion force, muscle fiber conduction velocity, median frequency, and average rectified value during maximum voluntary contraction were significantly smaller in the older than in the younger group (p < .05). These results suggested that the neuromuscular system in older subjects is affected by the selective atrophy of fast twitch fibers and differences in motor unit firing statistics. Our results suggest the utility of applying the EMG observed during maximum voluntary contraction to the noninvasive evaluation of neuromuscular function in elderly persons.

Polymorphisms in control region of mtDNA relates to individual differences in endurance capacity or trainability.

The purpose of this study was to investigate whether the polymorphisms in the control region of mitochondrial DNA (mtDNA) related to individual difference in the endurance capacity or trainability. Fifty-five sedentary males participated in this study and were submitted to an 8-week endurance training program. The VO(2 max) was determined before and after training. Total DNA was extracted from the blood, and the sequence of the mtDNA control region was determined. The polymorphism in the mtDNA control region was decided based on the "Cambridge sequence." In 29 of the 55 subjects, vastus lateralis muscle biopsy samples were taken at rest before and after the training program. MtDNA content and CS (citrate synthase) activity in skeletal muscle was measured as the phenotype of the polymorphisms in the mtDNA control region. The VO(2 max) increased to 48.2 +/- 6.3 ml/min/kg from 42.1 +/- 6.0 as a result of the 8-week training (p < 0.05). The numbers of polymorphisms in determined 1,122 bp were 11.1 +/- 2.9 variable sites per person, and the total numbers of polymorphisms were 125 variable sites. The subjects were classified into two groups at each variable site, the Cambridge sequence (Cam) group and the non-Cambridge sequence (non-Cam) group. There were significant differences in pre-VO(2 max) between the two groups at each mtDNA nucleotide positions 16298, 16325, and 199, and in % Delta VO(2 max) at 16223 and 16362. Twenty-nine subjects who underwent the biopsy revealed significant differences in pre-CS activity at 194 and pre-mtDNA content at 514. Also, significant differences were found in the change rate of VO(2 max )and CS activity as a result of training between the two groups at 16519. In conclusion, it suggested that mtDNA polymorphisms in the control region might result in individual differences in endurance capacity or trainability.

Air trapping and arboreal locomotor adaptation in primates: a review of experiments on humans.

A review was made of experiments on humans in which air trapping by glottis closure during three-dimensional movements were examined in four subjects including former Olympic gymnasts. In brachiation and horizontal bar exercises, the behaviour of the larynx was monitored with a fiberoptic endoscope, and EMG-data were recorded from shoulder muscles. The results revealed that immobilization of the polyaxial connection between the shoulder girdle and the thorax by air trapping occurs in phases of extreme loading of the upper limbs. The closure of the airway by the larynx in humans serves three functions: first, the prevention of errors in deglutition; second, the production of vocal sounds; third, the retention of air inside the thoracic cavity. The latter function, air trapping, allows the immobilization of the rib cage for the muscular fixation of the shoulder blade on the trunk in movements that imply unusually high external forces acting on the upper limbs. This morphological-functional innovation probably has been made when early mammals invaded the three dimensional arboreal habitat, because it gave the tree-dwelling early primates the device to anchor themselves by the arms alone and to avoid falling out of trees. The specific functional characteristic of primates is the hermetic closure of the vocal and vestibular folds by rapidly contracting muscles in the folds. So the closure of the glottis, which in humans seems primarily an adaptation to the production of vocal tones, seems to go back to the adaptation of Tertiary arboreal primates to movements in a three-dimensional environment. Our conclusions are in agreement with the results of other contributions to this volume.

Composition of myofiber types in the vocalis muscles involved in rapid closure of the glottis in Japanese macaques.

Myofiber types of the medial thyroarytenoid (vocalis) muscle, lateral thyroarytenoid muscle, and cricothyroid muscle of the Japanese macaque were examined with enzyme-histochemical methods. For comparison, the semitendinosus muscle of the Japanese macaque and the thyroarytenoid (vocalis) muscle of cattle, sheep, and pig were examined with the same methods. The vocalis muscle of the Japanese macaque was composed exclusively of fast-twitch/oxidative/glycolytic (FOG) myofibers; it differed from the lateral thyroarytenoid, cricothyroid, and semitendinosus muscles of the Japanese macaque and from the vocalis muscles of the other animals, which consisted of slow-twitch/oxidative, FOG-, and fast-twitch/glycolytic myofibers or type IIC myofibers. The histochemical properties of the vocalis muscle of the Japanese macaque show that the vocalis muscle has a capacity to close the glottis rapidly and completely.

Effects of fixation and preservation conditions on immunohistochemical profiles of the skeletal muscle fibers in Japanese macaques.

Effects of fixation and preservation conditions of muscle tissues on immunohistochemical profiles are investigated. Samples of the hind limb and epaxial muscles were removed from 4 adult female Japanese macaques (Macaca fuscata) fixated with 10% formalin and preserved in the same solution under different conditions for 6 months to 4 years and 6 months. Sections were stained with indirect immunofluorescence and avidin-biotin peroxidase complex methods using an antibody against fast myosin (Mouse Monoclonal Anti-skeletal Myosin-Fast, clone MY-32, Sigma) as a primary antibody. Clear responses to the antibody were demonstrated in the samples from the specimens fixated by injection or immersion with 10% formalin and preserved in the same solution for 6 months to 1 year and 6 months. Distribution patterns of the fibers reacting to the antibody coincided with that of the fast twitch fibers determined using enzyme-histochemical techniques in these samples. Clear responses to the antibody were not demonstrated in the samples from the specimen repeatedly rinsed in water for gross anatomical dissections during the preservation period. The results of this study warrant applications of immunohistochemical techniques to the study of fiber type composition in muscle samples from specimens fixated with formalin and preserved in the same solution for a long term.

Cross-sectional geometric properties along the diaphysis of femur and humerus in chimpanzees and humans.

The cross-sectional geometric parameters were determined serially along the diaphysis of 3 paired humeri and femora of chimpanzees by using the computed X-ray tomographic scans, and compared with those of humans. In magnitude, the femoral parameters were greater and humeral parameters were less, respectively, in humans than in chimpanzees. While the changing pattern among the parameters along the diaphysis was very similar both in the femur and humerus of chimpanzees, the pattern in the humans was reversed between the cross-sectional area and area moments of inertia. In chimpanzees, the femoral parameters increased toward the most proximal diaphysis, whereas humeral parameters yielded a moderate peak in a portion slightly proximal to mid-shaft. Potential mechanisms responsible for these findings were discussed.