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Scott M. Lephart and Timothy J. Henry

The confusion between the terms open kinetic chain and closed kinetic chain becomes even greater with application to the upper extremity. Upper extremity function is very difficult to define, due to the numerous shoulder positions and the great velocities with which the shoulder can move. Classifying exercises for rehabilitation of the upper extremity is very difficult due to the complexity of the joint. Many definitions and classification systems have been proposed; however, none of these entirely encompass rehabilitation of the upper extremity. Using previous classifications we have developed a Functional Classification System that is designed to serve as a template for upper extremity rehabilitation. This system has been designed to restore functional shoulder stability, which is dependent upon proper scapulothoracic and glenohumeral stability, and humeral control; all of these are in part mediated by neuromuscular mechanisms. The objective of our new Functional Classification System is to restore functional stability of the shoulder by reestablishing neuromuscular control for overhead activities.

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Timothy J. Henry and Lee Cohen

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Timothy J. Henry, Scott M. Lephart, Jorge Giraldo, David Stone, and Freddie H. Fu

Context:

Muscle fatigue is an important concept in regard to the muscle function of the shoulder joint. Its effect on the muscle force couples of the glenohumeral joint has not been fully identified.

Objective:

To examine the effects of muscle fatigue on muscle force-couple activation in the normal shoulder.

Design:

Pretest, posttest.

Patients:

Ten male subjects, age 18–30 years, with no previous history of shoulder problems.

Main Outcome Measures:

EMG (area) values were assessed for the anterior and middle deltoid, subscapularis, and infraspinatus muscles during 4 dynamic stabilizing exercises before and after muscle fatigue. The exercises examined were a push-up, horizontal abduction, segmental stabilization, and rotational movement on a slide board.

Results:

No significant differences were observed for any of the muscles tested.

Conclusions:

The results of our study indicate that force-couple coactivation of the glenohumeral joint is not significantly altered after muscle fatigue.