Comparison of Shoulder Rotation Strength and Test-Retest Reliability in 3 Test Positions With Swimmers.

Abstract

Context: Advancements in portable load-cell technology have enabled high-quality assessment of shoulder internal (IR) and external rotation (ER) peak force (Fmax) and rate of force development (RFD). This study's purpose was to explore the reliability and differences between IR and ER Fmax and RFD in different testing positions using a novel load-cell device.

Design: A within-subjects repeated-measures design was employed to compare the intersession values and reliability of Fmax and RFD for both shoulder IR and ER across 3 positions: seated-0°, supine-0° and supine-90°.

Methods: National-level swimmers (n = 19; age = 16.8 [1.0] y) completed 3 testing occasions of each condition (combination of arm, rotation, and test position) separated by 7 to 14 days.

Results: IR superseded ER in all testing positions. The association between these positions across IR and ER was typically strong for both Fmax and RFD (r > .85, P < .001) except for IR RFD (r = .56-.73, P < .05). For sessions 2 to 3, Fmax intraclass correlation coefficient and CV (intraclass correlation coefficient = .89-.96, CV = 5.2%-8.8%) were typically within acceptable ranges, whereas RFD (intraclass correlation coefficient = .74-.90, CV = 11.5%-18.1%) often exhibited inflated error.

Conclusion: The supine (90°) position was the most consistent position across both measures. Load-cell technology can be confidently used to assess shoulder rotation Fmax in 3 different positions, whereas RFD should be used with caution without protocol refinement.