SIGNIFICANCE AND DIFFERENCE OF FLEXOR MUSCULAR RELAXATIONS WITH AND WITHOUT EXTENSOR MUSCULAR CONTRACTION IN ARM MUSCLES / 体力科学

ABSTRACT

In the present report, significances of voluntary muscular relaxations were studied. Pattern of relaxation in elbow flexor muscles was examined in two conditions, with and without relaxation of contralateral muscles (Active Relaxation AR, Passive Relaxation PR, respectively) .<BR>EMG patterns of biceps were obtained in various experimental conditions to investigate characteristics of each muscular relaxations. Arm flexor strength was exerted with saw-tooth and square forms produced by Low Frequency Generator, and in other case the strength was voluntarily exerted as fast as possible.<BR>Muscular relaxation time was determined by the difference between begining of tension decrease and vanishing point of biceps spike discharge.<BR>The results were ;<BR>1) PR was faster than AR, but both relaxation times were prolonged following the increment of initial tension. There were no significant differences in the times between left and right arms, and between supine and prone positions of the forearm. Relaxation time in the square form muscular exertion was the fastest in AR.<BR>2) Quickness of the biceps relaxation in PR was significantly correlated with the velocity of extensor muscular contraction. (r=0.41)<BR>3) However, a transient excess tension development over the initial tension was observed at the initiation of relaxation in both conditions (less than 1 kg and 100 msec in most cases) . Both the excess tension produced and its duration were greater when the initial tension was higher. The rate of rise (g/msec) in PR was higher than AR.<BR>These results suggested that each muscular relaxation in this study was conducted by different inhibitory systems. The inhibitory system in Active Relaxation might be localized in higher level of the central nervous system than that of Passive Relaxation