Isokinetic Scapular Muscle Performance in Young Elite Gymnasts (Original Research) (Report‪)‬

The scapula plays a vital role in upper extremity function. The quality of movement depends upon the interaction between scapular and glenohumeral kinematics, especially in overhead sports where the demands on the shoulder are extremely high. (1) Recently, researchers (1,2) have described the function of the scapulothoracic joint in overhead movements as an important link in the sport-specific kinetic chain in which the scapula functions. The kinetic chain principle describes how the human body can be considered as a series of interrelated links or segments. Movement of 1 segment affects segments proximally and distally. (2) With respect to the kinetic chain, power, velocity, and accuracy of the throwing or smashing movement depend upon the quality of movement and stabilization of each link. For instance, during the throwing movement, the final outcome is the result of forces generated from the ground-reaction forces that come from the contralateral lower limb and are transferred in a diagonal pattern through the trunk into the throwing arm. Optimal positioning of every segment within the chain and functional muscle activation patterns from proximal to distal are the key premises in this transfer of energy. (2) Gymnasts are a group of athletes who use their arms extensively during their sport activity. (3,4) However, the starting and ending points of the kinetic chain in these athletes substantially differ from those of throwers. Hence, the relative role of the links in the chain, including muscle activation patterns, is likely different. Indeed, a unique aspect of gymnastics is the regular use of the upper extremities to support body mass. (5) Contrary to overhead throwing athletes who use their arms in an open kinetic chain, gymnasts use their upper extremities very often in closed kinetic chain activities with the hand supported on a floor, balance beam, or pommel horse. The additional task of weight bearing requires supplementary strength of the arm muscles and stability of all contributing joints. (3-5) Strong scapular muscles are among the major prerequisites for optimal stability and functional movement of the scapulothoracic joint. (1,6,7) Several investigators have studied scapular muscle adaptations in healthy overhead athletes who are involved in overhead sports, such as baseball (8) or volleyball, (9,10) that involve the primary use of their dominant arm. However; few investigators have examined scapular muscle performance in overhead athletes with bilateral use of their arms during their sports. Muscle strength of the scapular muscles and scapular position have been investigated only in swimming athletes. (11-13) Recently, Cools et a1 (14) developed an isokinetic protocol for the measurement of scapulothoracic protraction and retraction muscle strength. Normal nonathletic subjects and overhead athletes have been evaluated with this procedure. (9,14,15) Scapular muscle adaptations in young gymnasts, however, have not been examined. Therefore, the purpose of our study was to compare the isokinetic muscle performance of the scapular muscles between elite adolescent gymnasts and nonathletic adolescents to identify differences in strength, endurance, and muscle balance based on high-level sport participation.