Anthropometric Normalization Applies to Elbow Varus Torque, but Not Ulnar Collateral Ligament Properties in Collegiate Pitchers

Authors

Dylan Bakhshi, University of Southern CaliforniaFollow
Adam J. Barrack, University of Southern CaliforniaFollow

Abstract

BACKGROUND AND PURPOSE: Elbow varus torque (EVT) is used as a surrogate measure for ulnar collateral ligament (UCL) injury risk in baseball pitching. EVT is often normalized to pitcher anthropometrics to account for body size, but it is unclear if these are appropriate. If UCL structure is not related to body size, normalizing EVT to body size may compromise its relevance to injury risk. This study examined whether body size is associated with EVT or UCL structure to determine if body size is an appropriate ratio normalization for both EVT and underlying UCL structure in collegiate baseball players.

METHODS: 38 Healthy Division 1 collegiate pitchers were recruited. The throwing arm elbow was imaged using ultrasound (US) with participants in sidelying with the shoulder and elbow flexed to 90°. The UCL was imaged longitudinally, first with the forearm at rest, then with a 2.5kg valgus load applied to the distal wrist. UCL laxity was defined as the difference in ulnohumeral gap width (peak of humeral trochlea to ulnar coronoid process) between rest and gapped conditions. UCL cross-sectional area (CSA) was measured by tracing the borders using US calipers. The average of two trials was used. EVT was measured using a forearm-mounted inertial sensor and quantified as the average of 5 max-effort fastballs. Associations between anthropometrics (weight, height and weight*height), EVT, elbow laxity and CSA were tested using Pearson correlations. For significant associations, appropriateness for ratio normalization was assessed by correlating the ratio-normalized variable with its denominator; an appropriate normalization reduces (and ideally eliminates) the association.

RESULTS: All pitcher anthropometrics were significantly related to EVT (r=0.54-0.76, p 0.05).

CONCLUSION: Body size was related to EVT, but not UCL structural properties in collegiate pitchers. EVT ratio normalization was most warranted for weight and weight*height. Since UCL structure was not related to body size, normalizing EVT to body size may compromise its relevance to underlying UCL anatomy, and with it, risk for injury.

Recommended Citation

Bakhshi, Dylan and Barrack, Adam J. (2025) "Anthropometric Normalization Applies to Elbow Varus Torque, but Not Ulnar Collateral Ligament Properties in Collegiate Pitchers," International Journal of Exercise Science: Conference Proceedings: Vol. 14: Iss. 5, Article 41.
Available at: https://digitalcommons.wku.edu/ijesab/vol14/iss5/41