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Effect of an eccentric exercise bout on concentric power of the shoulder.

Introduction: Eccentric exercise often results in decreases in strength parameters such as concentric torque production. Previous research has been limited to the effect of eccentric exercise on torque production of the elbow flexor and knee extensor musculature. No known research has focused on its effect on the shoulder musculature. Also, no evidence showing the effect of eccentric exercise on concentric power of any musculature has been found. Purpose: To determine the effect of an eccentric bout of exercise on concentric power of the shoulder musculature. Methods: Participants consisted of forty-one college-aged students who were free of any shoulder pathologies. Participants were randomly assigned to one of two groups, control (CON) (n=22), and experimental (EXP) (n=19), with the experimental group undergoing a bout of eccentric exercise between pre- and post-tests. Participants were familiarized with the study protocol on the Biodex Isokinetic Dynamometer (Biodex, Inc., Shirley, NY) two days before testing. Day one (D1) cons isted of a power spectrum analysis (PSA) consisting of five repetitions of concentric internal rotation of the shoulder at each of six speeds including 60, 120, 180, 210, 240, and 300 deg/sec. Mean and peak torque (mT and pT) and mean and peak average power (mAP and pAP) outputs were recorded for each of the six velocities. Day two (D2) consisted of a bout of 50 repetitions of maximal eccentric activity of the internal rotators for the experimental group followed immediately by the PSA. Members of the control group simply underwent the PSA. Analysis: Changes in criterion measures between groups, days and test velocities (2x2x6) were measured with four separate repeated measures ANOVAs. Wherever a significant main effect was present, a post hoc analysis was used to detect difference in the measures. Results: Contrary to the hypothesis, there were no significant changes (p<0.05) in mT, pT, mAP, or pAP between groups. There were also no significant differences (p<0.05) in any of the measures across days. A significant main effect was present for velocities (p<0.05) for all dependent variables. Discussion: Changes in torque and power production after an eccentric bout may not be as apparent in the shoulder musculature. Previous research focused on larger, more isolated muscle groups such as the elbow flexors and knee extensors. Further research must be conducted to determine the effects of eccentric activity on concentric shoulder power.

Iveland, S., Noffal, G., Brown, L., Zinder, S., and Koob, R.

Movement Analysis Laboratory, Department of Kinesiology and Health Science, California State University, Fullerton, CA
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Author:Iveland, S.; Noffal, G.; Brown, L.; Zinder, S.; Koob, R.
Publication:Clinical Kinesiology: Journal of the American Kinesiotherapy Association
Article Type:Clinical report
Geographic Code:1U9CA
Date:Mar 22, 2005
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