T he shoulder girdle is an arrangement of three bones, four articulations, and numerous muscles which must interact in a highly coordinated and complex manner in order to elevate the arm and position the hand for use. Because the glenohumeral joint is highly mobile and inherently unstable, it is essential that the scapula and corresponding musculature perform several crucial functions. While some authors (3,12) state that normal scapular orientation at rest maintains the glenoid surface in an u p ward tilt which enhances passive stability of the glenohumeral joint, others (1 1,16) state that the resting position of the glenoid fossa is downward. During elevation of the arm, the scapula must follow the humeral head with a lateral or upward rotation in order to facilitate congruency of the glenohumeral joint and, thus, maximize stability. It is also imperative that the acromion process elevate and rotate in relation to the greater tuberosity of the humerus in order to avoid impingement of soft tissues in the subacromial space. In addition to demands for mobility, the scapula must also be capable of dynamic stability during arm elevation in order to afford the movers of the glenohumeral joint a stable base with which to position the arm.

Forty-eight, healthy, adult, volunteer subjects (20 males, 28 females) who ranged in age from 21-46 years were studied during isokinetic testing of the knee joint. The same knee of each subject was tested at speeds of 60, 180, and 240°/sec on both the Biodex Model 8-2000" and the Cybex I 1 Plus' isokinetic dynamometers. The following variables were compared: peak torques, angle of peak torques, peak torque to body weight ratios, and flexion to extension ratios. Analysis of correlation coefficients showed statistically significant (p < 0.05) relationships between several pairs of values. However, results of paired t-tests revealed many statistically significant (p < 0.05) and nonuniform differences. The nonuniform differences between data generated by the two brands of isokinetic dynamometers indicated that clinicians should exercise caution when attempting to extrapolate test data from one machine to another.Isokinetics, a concept introduced in 1967 (36, 59), has gained popularity in a variety of clinical applications. lsokinetic technology is used to strengthen muscle and to assess dysfunction (19,20,29,39,42,43,56,60). Other uses for isokinetic dynamometers include passive stretching, preemployment screening, industrial rehabilitation, determining return to competition status, and research (1 1, 24, 45, 46 0190-601

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