The effect of change in movement direction in relation to gravity on control strategy and rate of electromyography rise in fast single joint elbow movements

The purpose of this research was to study the effect of change in movement direction in relation to gravity on control strategy and rate of electromyography rise in fast single joint elbow movements. Fifteen right handed men without any history of neuromotor injury (mean age of 24.8 ± 3.8 year) participated in this study. We asked of subjects to perform elbow flexion as fast as possible in seven different directions in respect to gravity with 90 percent of full range of motion. While they were performing movements surface electromyography done from biceps and lateral head of triceps. By dividing electromyography activity range (peak activity minus rest activity) on time range of activity (time of peak activity minus time of onset) slop of receive to peak of electromyography or rate of electromyography rise computed. Data analyzed by use of repeated measure intracase variance analyze (P 0.05). There were not any different in biceps muscle but rate of electromyography rise had significant different between movement in horizontal plane around vertical axis with movement in sagittal plan around frontal axis(against gravity), sagittal plan around frontal axis(with gravity), supine and dangle positions in triceps muscle. Movement direction in relation to gravity cause to use simultaneously of speed sensitive and speed insensitive strategies in fast single degree of freedom elbow flexion and had significant effect on rate of electromyography rise in triceps muscle.