Guillermo J Noffal1. 1. California State University, Fullerton, California 92834-6870, USA.
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 degrees and the elbow flexed to 90 degrees. 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.
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 degrees and the elbow flexed to 90 degrees. 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.
Authors: Kevin M Kaplan; Neal S Elattrache; Frank W Jobe; Bernard F Morrey; Kenton R Kaufman; Wendy J Hurd Journal: Am J Sports Med Date: 2010-11-03 Impact factor: 6.202
Authors: Wendy J Hurd; Kevin M Kaplan; Neal S ElAttrache; Frank W Jobe; Bernard F Morrey; Kenton R Kaufman Journal: J Athl Train Date: 2011 May-Jun Impact factor: 2.860