Effect of exercise at light loads with manipulative resistance on infraspinatus, trapezius (upper fiber) and deltoid (middle fiber) muscle activities in shoulder joint elevation.

[Purpose] To clarify rotator cuff muscular activity in the raised position of the closed kinetic chain (CKC) exercise. [Subjects] Twenty-nine cases were studied, 19 men and 10 women (average age 21.5 +/- 4.7 years old, average body weight 60.1 kg +/- 11.4). [Methods] To determine the effects of the closed kinetic chain exercise on the upper limb, we measured the surface EMG of the infraspinatus muscle, the trapezius (upper fiber) and the deltoid (middle fiber) with the arm elevated. [Results] Our results show that at an elevation angle of 150 degrees in the scapular plane of the upper limb, with 5% body weight load, the EMG activities of the infraspinatus muscle are approximately 30% of maximum voluntary contraction (MVC). [Conclusion] The raised position of the CKC exercise is effective in physical therapy for functional recovery of the infraspinatus muscle.