Changes in Normalized Shoulder Strength and Self-Perceived Function in Healthy Division One Baseball Players Over the Course of a Competitive Season.

Background: Deficits in shoulder strength have been previously established as a risk factor associated with the development of time-loss shoulder and elbow injuries. However, limited data exists on normative shoulder strength changes in collegiate baseball athletes over the course of a competitive season. Hypothesis/Purpose: There were two purposes of this study: 1) to assess changes in shoulder strength over a competitive season, and 2) to assess self-perceived shoulder and elbow function changes over the course of a competitive season in healthy Division I collegiate baseball players. It was hypothesized that shoulder strength would differ over a competitive season with no observed differences in Kerlan-Jobe Orthopaedic Clinic (KJOC) scores over time in healthy baseball athletes.

Study design: Prospective cohort.

Methods: Forty-nine uninjured NCAA baseball athletes were assessed for bilateral isometric shoulder strength (external [ER] and internal [IR] rotation and scaption [SCAP]) via handheld dynamometry at four time points: fall physicals, preseason, mid-season, and postseason. Additionally, athletes completed the KJOC score at each testing session. A 2x4 repeated measures multivariate analysis of variances was conducted to determine the effect of playing position and time on normalized shoulder strength and KJOC scores.

Results: There was a main effect of time on isometric shoulder strength (p < 0.001). There was no effect for position (p = 0.88), or interaction effect of position and time (p = 0.643). Pairwise comparisons demonstrated differences across time in dominant limb ER (p = 0.01) and SCAP (p < 0.001), and non-dominant limb ER (p < 0.001), IR (p = 0.004) and SCAP (p < 0.001). There were no differences over time for dominant limb IR (p = 0.131) or KJOC scores (p = 0.154).

Conclusion: Uninjured collegiate baseball players demonstrated changes in shoulder strength over time that exceeded minimal detectable change scores over the course of a competitive season for both limbs. The results of the present study offers shoulder strength values using a reliable and reproducible normalization method to evaluate shoulder strength in collegiate baseball athletes.

Level of evidence: III.