EFFECTS OF VIBRATION APPLIED ON FOREARM AND UPPER LIMB MUSCLES ON HUMAN VOLUNTARY MULTI-WRIST AND ELBOW MOVEMENTS / 体力科学

The effect of forearm and upper limb muscles vibration during extension and flexion movement of wrist and elbow was studied in 10 normal human subjects. In first experiment, a vibratory stimulation was applied to either the flexor carpi ulnaris (FCU) or the biceps brachii (BB) muscle during simple and simultaneous extension movement about wrist and elbow. In second experiment, vibratory stimulation was applied to either the extensor carpi radialis (ECR) or the triceps brachii (TB) muscle during simple and simultaneous flexion movement about wrist and elbow. The main new findings of the present study are as follows. During simple and simultaneous extension-flexion movements of the elbow, the application of vibration to the FCU or to the ECR produced an undershoot of the target position. However, no undershoot was observed by the application of vibration to the BB or the TB during simultaneous extension-flexion movements of the wrist. From these results, it was revealed that although there are cases where the phenomenon of undershoot resulting from vibration of the wrist and elbow during simple and simultaneous movements corresponds to the type of synaptic connection from muscle spindle group Ia sensory inputs to alpha motor neurons, as identified by Cavallari & Katz (1989) and Cavallari et al. (1992), the manifestation of undershoot is influenced by differences between the movement patterns of the wrist and elbow joints, as well as the differences between simple movement and simultaneous movement.

EFFECT ON DECLINE IN HEART RATE INDUCED BY OCULAR COMPRESSION AND APNEA AFTER EXERCISE / 体力科学

<b>Object </b>: The purpose of this study was to test the response of the decline in heart rate (HR) induced by compression on the eyeball (eyeball pressure : EP) and voluntary non breath (VNB) after pedaling exercise. <b>Methods </b>: EP ; Nine male subjects performed exercise for 3 min in a supine position using a bicycle ergometer. Immediately after the exercise all subjects received EP for 10 seconds. After that, subjects undertook the same protocol without EP (CON-E). VNB ; Four male and two female subjects performed exercise for 5 minutes using a bicycle ergometer. Immediately after the exercise subjects received VNB for 7 seconds. After that subjects undertook the same protocol without VNB (CON-V). <b>Results </b>: The slope of the decline in HR recovery (HR_DS) after exercise in EP increased significantly more than that in CON-E (p<0.05). However, time constant (HR_TC) in CON-E declined faster than that in EP. Thereby, the relationship between HR_DS in EP and HR_TC in CON-E correlated (r=-0.562). The HR_DS of VNB was greater than that of EP and CON-V. However the relationship between HR_DS in VNB and HR_TC in CON-V did not correlate. <b>Conclusion </b>: We suggest that EP affects vagal nervous activity and VNB affects strength of baroreflex sensitivity. Therefore HR_DS of EP might evaluate vagal nervous activity.

Effect of Visual input on stretch responses of ankle muscles during movements to absorb impact / 体力科学

The purpose of this study was to examine the effect of the different visual and vestibular inputs on EMG response of ankle muscles during movement to absorb impact in sliding down a slope. Thereby, our research focused on the relationship between preactivation (PA) in central program and stretch reflex induced by dorsiflexion immediately after impact. The subjects were nine healthy males. Movements were conducted using a special sliding apparatus. Conditions included sliding down a lower 15°slope with eyes open (Low) and with eyes closed (Low-Closed), and a higher 20°slope with eyes open (High) . PA prior to impact indicated the co-contraction of the medial gastrocnemius (MG) and tibialis anterior (TA) . PA levels in those muscles were significantly higher during High than during Low-Closed (p<0.05) . In contrast, PA of the coleus (Sol) was low in all test conditions. After impact, however, the stretch reflex of Sol during Low-Closed was greater than other test conditions. Because muscle stretch velocities and PA levels of Sol among all test conditions remained unchanged, these results suggest that different visual inputs could change the response of stretch reflex by modulations in reflex gain.