Savitzky, JA, Abrams, LR, Galluzzo, NA, Ostrow, SP, Protosow, TJ, Liu, SA, Handrakis, JP, and Friel, K. Effects of a novel rotator cuff rehabilitation device on shoulder strength and function. J Strength Cond Res 35(12): 3355–3363, 2021—The glenohumeral joint, a multiaxial ball and socket joint, has inherent instability counterbalanced by the muscular stability of the rotator cuff (RC) and connective tissue. Exercise has been shown to alleviate pain and disability arising from degenerative changes of the RC due to overuse, trauma, or poor posture. This study compared the training effects of ShoulderSphere (SS), an innovative device that uses resistance to centrifugal force, to TheraBand (TB), a traditional device that uses resistance to elasticity. Thirty-five healthy male and female adults (24.2 ± 2.4 years) were randomized into 3 groups: SS, TB, and control. Five outcomes were assessed before and after the twice-weekly, 6-week intervention phase: strength (shoulder flexion [Fx], extension [Ext], external rotation [ER], and internal rotation [IR]), proprioception (6 positions), posterior shoulder endurance (ShEnd), stability (Upper Quarter Y-Balance Test [YBal] (superolateral [YBalSup], medial [YBalMed], and inferolateral [YBalInf]), and power (seated shot put [ShtPt]). Data were analyzed using a 3 (group: SS, TB, and control) × 2 (time: pre and post) generalized estimating equation. Analyses demonstrated a main effect of time for all strength motions (p < 0.01): YBalInf (p < 0.0001), ShtPt (p < 0.05), and ShEnd (p < 0.0001) but no interaction effects of group × time. There were no main or interaction effects for proprioception. Both SS and TB groups had significant within-group increases in Ext, IR, YBalInf, and ShEnd. Only the SS group had significant increases in ER, Fx, and ShtPt. ShoulderSphere demonstrated comparable conditioning effects with TB and may afford additional strength gains in Fx and ER, and power. ShoulderSphere should be considered a viable alternative in RC conditioning.