• P.H. Vint
  • P.W. Castagno
  • D.M. Drewlinger
  • T.D. Royer
  • J.G. Richards


Accurate quantification of muscular strength is critical in the prevention and reduction of shoulder injuries. Since the introduction of the first isokinetic &vice in 1965, the methods of isolated joint testing have essentially remained unchanged. Historically, bilateral joint testing has been performed asynchronously, comparing values obtained while testing one side of the body at a time. While numerous investigators have examined the effects of alternative testing positions on shoulder strength parameters, none have attempted to collect isokinetic data for both sides of the body simultaneously (synchronously). The purpose of this study was to compare the facilitation of torso stability and the production of shoulder strength during synchronous and asynchronous bilateral isokinetic exercise. Two Cybex I1 isokinetic dynamometers and the Upper Body Exercise Table (U. B. X. T) were used to collect data from 12 male collegiate athletes. Six individuals have been previously evaluated with, and treated for. various shoulder dysfunctions, while the other six have had no prior history of significant shoulder pain or injury. Five different shoulder exercises were performed, each at speeds of 90 and 180"Isec. These exercises include shoulder abduction/adduction, flexion/extension, horixontal flexion/extension, internal/external rotation in the neutral position, and interna4external rotation in the supine position with 90° abduction. Each shoulder test will be set up and performed in the position recommended in the Cybex Handbook for Isolated Joint Testing and Exercise with the exception of IR/ER(Neutral). The W R (Neutral) tests were performed with the humerus elevated to position of 20 to 30' abduction to avoid impingement on the vascularity of the supraspinatus tendon. A two way repeated measures analysis of variance was employed to reveal if significant differences existed in mean peak torque production. Torso stability during exercise was quantified and evaluated using three dimensional high speed video equipment. Six joint markers were used to define the torso. Stabilization parameters were examined in two ways. First, the extraneous motion of the shoulders were determined by calculating the variance of the net linear displacement of each shoulder marker in three orthogonal planes. Second, the displacement of the shoulder pint instant center of rotation away from the torque input axis of the dynamometer were estimated by computing the angular position of the shoulder segment in three-dimensional space. Video data were time dilated. averaged] then presented through graphical analysis.