Electromyographic activity of the shoulder muscle at 20 and 90°abduction (20 Abd, 90 Abd) during external rotation was investigated in seven healthy men with no history of injury or instability of the shoulder joint.
Electromyography (EMG) was recorded using intramuscular fine-wire electrodes inserted into the M. Supraspinatus, M. Infraspinatus and M. Teres minor, and with bipolar surface electrodes on the middle and posterior parts of M. Deltoid anti the upper and middle parts of M. Trapezius. To compare activity in different muscles, the integrated EMG (iEMG ) activity of each muscle was normalized.
M. Infraspinatus and M. Teres minor showed significantly higher activity at both the 20 Abd and 90Abd compared with the middle and posterior parts of M. Deltoid and upper parts of M. Trapezius. M. Supraspinatus, the middle and posterior parts of M. Deltoid, and upper and middle parts of M. Trapezius all showed a difference in activity level between the two positions.
These findings suggest that when M. Infraspinatus and M. Teres minor contribute to external rotation as a stabilizer and prime mover, consecutively, M. Supraspinatus, the middle and posterior parts of M. Deltoid, and upper and middle parts of M. Trapezius function according to the positions. Moreover, the activity of the upper and middle parts of M. Trapezius in 90Abd should influence stabilization, adduction and upward rotation of the scapula. Therefore, we conclude that the external rotation position is closely related to shoulder muscle activity and coordination.

The purpose of this study is to identify the effect of position (full can, empty can) and change of angle on the activity of shoulder muscles during scapular plane abduction ; and also to examine its application to exercises used for rehabilitation of shoulder muscles. Seven healthy subjects (23.4±1.4 yr) with normal shoulder function performed scapular plane abduction with external rotation (full can) and scapular plane abduction with internal rotation (empty can) . An electromyogram was recorded with a fine wire intramuscular electrode at the supraspinatus, deltoid anterior, middle, posterior and trapezius upper with bipolar surface. The EMG activity (RMS) of each muscle was normalized by the highest EMG activity (100%RMS) during a maximum manual muscle test for each muscle (%RMS) . The %RMS of each muscle remarkably increased with a change of the angle for empty can, whereas it showed a slight increase with a change of the angle for full can. This finding suggests that the position of full can and empty can in scapular plane abduction affects the function of shoulder muscles. In addition, full can exercise is recommended in order to improve function of the supraspinatus and the muscular activity balance between the supraspinatus and the deltoid. Empty can exercise is applied to sport-specific exercise for rehabilitation of shoulder muscles.

The higher anterior cruciate ligament (ACL) injury rate of females is one of the most sever athletic-related problems today. The purpose of this study is to compare the lower extremity kinematics between male and female during single leg landing.Six male and four female healthy subjects participated in this study. They jumped from a 32 cm high box and landed with the dominant leg. The landing action was filmed with three video cameras. The knee flexion, knee valgus/varus, and hip adduction/abduction angle and angle velocity were calculated.In female subjects, the knee flexion angle and hip adduction angle were greater compared to males. Also, the knee valgus velocity and hip adduction velocity were higher in females.Our results suggest that knee valgus kinematics may be related to hip adduction. It is important to evaluate hip kinematics when considering knee kinematics to prevent knee ligament injuries.