스포츠심리학 / 난이도지수의 조작방식에 따른 근육활동유형의 차이 = Differences in muscle activation patterns as a function of the way to manipulate index of difficulty

다국어 초록 (Multilingual Abstract)

The purpose of this study was to investigate differences in muscle activation patterns as a function of the way to manipulate index of difficulty(ID) by analyzing the intensity and ratio of agonist and antagonist muscle activities emerged during rapid single-joint movements in various target size and movement distance conditions. Nine subjects performed elbow extension movements toward a spatial target in two task conditions: target size and movement distance. IDs of two task conditions were kept constant by modulating target size and movement distance in the target size condition and movement distance condition respectively. For each movement, peak elbow angle, movement time, and the intensity and ratio of preprogrammed and on-line modulated muscle activities were calculated. The movement time was shown to increase with ID in both task conditions, although the amount of change was larger in the distance condition. The intensity of antagonist muscle activity measured from 30ms after movement onset to the time the elbow reached peak angle was shown to increase with ID in the distance condition, whereas it was found to decrease with ID in the target size condition. Also, while the ratio of on-line modulated agonist activity to antagonist activity increased with ID in the distance condition, it was not different between IDs in the target size condition. These results suggest that the ID of movements imposes different constraints on the movement control process according to the way it is manipulated. While the control system satisfies the task requirements by reducing the intensity of agonist and antagonist activities when ID increases by a decrease in target size, it achieves the movement goal by increasing the agonist muscle activity when ID increases by an increase in movement distance. Therefore, rather than an absolute principle for the relationship between ID and movement time, Fitts` law can be considered as an equation on the relationship between motor output and task situation which is secondary to the effect on the programming of motor commands of the task difficulty perceived by performer on the basis of knowledge about intended movement amplitude and tolerated variability in movement end-point.