Isokinetic eccentric-to-concentric strength ratios of the shoulder rotator muscles in throwers and nonthrowers.
Level 4 - case-series / case-control
Cross-sectional comparative laboratory study of athletic cohorts without prospective follow-up
PubMed 12860541 · doi:10.1177/03635465030310041001
What was done
Controlled laboratory study measuring bilateral shoulder rotator strength in 59 men (16 throwers, 43 nonthrowers). Eccentric external rotator and concentric internal rotator peak torques were assessed isokinetically at 300 deg/sec in the supine position with the shoulder abducted to 90 degrees and elbow flexed to 90 degrees to calculate functional strength ratios.
What was found
Throwers had significantly lower functional ratios than nonthrowers in their dominant limb, with no significant difference observed between groups in the nondominant limb. The lower ratio in throwers was driven by significantly greater concentric internal rotation torque without a concomitant increase in eccentric external rotation torque. The abstract reports no numerical values, variances, or exact p-values.
Why it matters
Repetitive throwing appears to disproportionately develop concentric internal rotation strength without matching eccentric external rotation decelerator capacity, creating a measurable functional imbalance in the dominant arm.
Limits
No raw torque values, ratios, or effect sizes are provided in the abstract. The throwing group was small (n = 16) and restricted to men. The cross-sectional design does not evaluate whether these strength ratios correlate with actual injury occurrence.