運動経験による伸張反射の調節能力の相違

抄録

Little attention has been given to the point that stretch reflex responses, including the long latency component, are modulated by motor preparation on the basis of movement experiences. In this paper I would like to examine the effect of movement experiences on the ability for modulation of stretch reflex in wrist flexor. The subjects were 39 healthy males, comprising 10 sprinters, 10 long distance runners, 10 kendo players and 9 non-athletes. When the subjects felt a rapid angle displacement in the direction of wrist extension, that is a stretch stimulus to the wrist flexor, they were required to perform further extension movement as quickly as possible in extension reaction tasks. In non-action tasks, the subjects were required to refrain from making any voluntary movements to the same stretch stimulus applied to the flexor. A DC torque motor was used to give the stretch stimulus. The short and long latency components of the stretch reflex could be measured by averaging the rectified electromyogram recorded with surface electrodes over the wrist flexor. The main results were as follows: The stretch reflex activities, particularly the long latency component of the wrist flexor in extension reaction tasks decreased in comparison to that in non-action tasks for all subjects. The degree of decreased reflex activities in kendo group, sprinter group, long distance group and non-athlete group were larger in that order. Moreover, the significant correlation was observed between the degree of decrease in reflex activities and the length of electromyographic reaction time during the extension reaction movements. Therefore, it is concluded that the ability for stretch reflex modulation with the appropriate motor control is closely connected to good performance of reaction movements and the degree of stretch reflex modulation directly reflects the difference of movement experiences accumulated for a long time.