Purpose
The purpose of this study is to estimate the normal rotator cuff function with IEMG.
Methods
40s houlders of 20 normal cases were studied. We selected the muscles at each motion and estimated these functions with IEMG.
Results
The IEMG activity of the supraspinatus and trapezius muscles was shown with the arm at the side and these activities increased with the load. The IEMG actitity of the deltoidus, supraspinatus and trapezius muscles increased during elevation in the scapular plane. But the infraspinatus did not demonstrate any remarkable activity. The IEMG activity of the supraspinatus, deltoideus and biceps brachii muscles increased with the load at 45° elevated position in the scapula plane. The IEMG activity of the biceps brachii in external rotation was higher than that in the neutral position at 45° elevated position. The regression coefficients between the torque and IEMG activity of the supraspinatus, deltoideus and biceps brachii muscles were higher than the infraspinatus. The ratio of IEMG activity of the supraspinatus to deltoideus at 45 ° elevated position was almost 2: 1irrespective of the load. In these cases with shoulder disorder, the correlation of the IEMG between the supraspinatus and the deltoideus changed. We consider this condition is to be imbalance between the inner and outer muscles.
