ABSTRACT
To investigate the effect of the glenohumeral internal rotation deficit (GIRD) improving rehabilitation program in high school baseball players on the change in muscle strength balance and pain of their shoulders. Seventy-six players (35 control group, 41 experimental group) participated in this 6-month study, from April, 2012 to September, 2012. The rehabilitation program (sleeper stretch) was carried out by coaches of experimental group. The experimental group showed a significant decrease, while the control group didn't show significant change in GIRD. The shoulder flexion-extension isokinetic strength ratio of experimental group changed only slightly, while that of control group experienced a bigger change. Experimental group players initially had high frequency of shoulder pain, but decreased to 53% at the end. Also, the Short Form-36 Health Survey showed the increase of total score. GIRD improving rehabilitation program helps to maintain the balance of shoulder extension-flexion strength ratio and relieve shoulder pain in the baseball players.