Abstract
Background: One of the possible mechanisms leading to shoulder injury may be a strength imbalance between those muscles that accelerate the upper limb and those responsible for deceleration. Many studies have examined shoulder balance through a concentric strength ratio of external and internal shoulder rotator muscles.
Hypothesis: A functional external eccentric-to-internal concentric ratio may be a better identifier of muscular imbalance in dominant and nondominant shoulders of throwers and nonthrowers.
Study Design: Controlled laboratory study.
Methods: Eccentric external and concentric internal peak torques were measured bilaterally in 59 men (16 throwers and 43 nonthrowers) at 300 deg/sec. Subjects were tested in the supine position with the shoulder abducted to 90° and the elbow flexed to 90°.
Results: Throwers exhibited significantly lower ratios than nonthrowers in their dominant limb; there was no difference between groups for the nondominant limb.
Conclusions: The lower ratio in the throwers' dominant limb was attributed to significantly greater concentric internal rotation torques without concomitant eccentric external torque gains.
Clinical Relevance: Rehabilitation and injury prevention regimens that include functional exercises to improve eccentric external rotation strength may bring more balance to the dominant shoulder of throwing athletes.
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