Effects of Repetitive Reaching Movements on Performance and Postural Control

Abstract

[Purpose] The purpose of this study was to examine whether muscle activity and joint movement in the lower limbs related to postural control are affected by repetitive reaching movements. [Methods] Fourteen healthy subjects attempted to reach a small target as fast as possible while standing. The target was placed at approximately the maximum reach distance. The reaching movement was repeated 50 times. Positions of each body segment were measured by three-dimensional motion analysis. Surface electromyograms (EMG) of tibialis anterior (TA) and gastrocnemius (GAS) were recorded. Parameters related to reaching performance and postural control were analyzed. [Results] With repetition of reaching movements, movement time and peak reaching velocity related to performance significantly increased. In addition, the onset of the EMG activity of TA appeared earlier, the integrated EMG activity of TA and GAS increased, and the maximum ankle dorsiflexion angle increased significantly. Changes in postural response were correlated with those of reaching performance. Moreover, postural response changed earlier than reaching performance. [Conclusion] Changes in postural control were induced by repeated reaching movements. These results suggest that changes in postural control associated with the central nervous system occur in advance in order to improve reaching performance.