Reliability of the Force Frame with and without a Fixed Upper-Limb Mold in Shoulder Rotation Strength Assessments Compared with Traditional Hand-Held Dynamometry

Abstract

Context: An imbalance between shoulder internal rotation (IR) and external rotation (ER) strength in athletes is proposed to increase the risk of sustaining a shoulder injury. Hand-held (HHD) and externally fixed dynamometry are reliable forms of assessing shoulder IR and ER strength. A new externally fixed device with an attachable fixed upper-limb mold (The ForceFrame) exists; however, its reliability in measuring shoulder strength is yet to be investigated. Objective: To determine the test–retest reliability of the ForceFrame, with and without the fixed upper-limb mold, in the assessment of shoulder IR and ER strength, as compared with HHD. Design: Test–retest reliability study. Setting: Laboratory, clinical. Participants: Twenty-two healthy and active individuals were recruited from the university community and a private physiotherapy practice. Main Outcome Measures: Maximal isometric shoulder IR and ER strength was measured using the ForceFrame and traditional HHD in neutral and at 90° shoulder abduction. Mean (SD) strength measures were calculated. Test–retest reliability was analyzed using intraclass correlation coefficients (3, 1). The SEM and minimal detectable change were calculated. Results: Good to excellent test–retest reliability was found for all shoulder strength tests across HDD and ForceFrame dynamometry (intraclass correlation coefficients [3, 1] = .854–.916). The minimal detectable changes ranged between 25.61 and 41.84 N across tests. Test–retest reliability was not affected by the dynamometer or testing position. Conclusions: The results from this study indicate that both the ForceFrame and HHD are suitable for measuring shoulder strength in clinical practice. The use of the fixed upper-limb mold with the ForceFrame does not improve reliability.