Shoulder Internal and External Rotation Strength Assessment in Baseball Pitchers: Normative Data and Reliability

Abstract

Rotator cuff strength assessments are valuable for monitoring throwing athlete injury and performance status. Portable technology enables "in-field" assessment and, therefore, increases utility. The purpose of this study was to quantify the reliability of strain gauge technology for measuring shoulder rotator strength and provide normative strength values for high school and college pitchers. Subjects (n = 15) participated in 3 testing sessions consisting of 5 maximal isometric shoulder internal rotation (IR) and 5 external rotation trials separated by 7 days. Variables of interest included peak force (Fmax), peak torque (Tmax), rate of force development, and rate of torque development. Coefficients of variation ranged from 4.3 to 5.8% for peak values and 16.0-28.5% for rate measures. Intraclass correlation coefficient estimates ranged from 0.79 to 0.89 for peak values, and 0.80-0.91 for rate measures, with IR typically marginally better than ER. Although practitioners need to be mindful of managing error (e.g., through familiarity), peak measures of rotator cuff strength assessed using portable strain gauge are promising for simple field-based monitoring of shoulder health for throwing athletes.