Effects of Hip Abduction Fatigue on Trunk and Shoulder Kinematics During Throwing and Passive Hip Rotational Range of Motion.

CONTEXT: Hip abductor musculature contributes to the stability of the pelvis, which is needed for efficient energy transfer from the lower extremity to the upper extremity during overhead throwing.

OBJECTIVE: The purpose of this study was to examine the effects of a hip abduction fatigue protocol on overhead throwing kinematics and hip passive range of motion.

DESIGN: Prospective cohort study.

SETTING: Laboratory setting.

PARTICIPANTS: A convenience sample of nineteen collegiate female softball players (20.6 ± 1.9 years; 169.3 ± 9.7 cm; 73.2 ± 11.2 kg).

MAIN OUTCOME MEASURES: Repeated hip abduction on an isokinetic dynamometer to fatigue was performed on three consecutive days. Trunk and shoulder kinematics and hip internal and external range of motion were analyzed prior to fatigue on day one and after the fatigue protocol on day three.

RESULTS: Repeated measures analysis of variance revealed no statistically significant differences in trunk and shoulder kinematics pre- and post-fatigue. A statistically significant time by side by direction interaction (F2,36 =5.462, p=0.018, ƞ2 p =0.233) was observed in hip passive range of motion. Post hoc simple effects tests determined a decrease in throwing side hip internal rotation pre- to post-fatigue (mean difference = -2.284; 95%CI = -4.302, -0.266; p=0.029).

CONCLUSION: The hip abductor fatigue protocol utilized in this study did not significantly alter trunk and upper extremity throwing kinematics. The lack of changes may indicate that fatigue of the hip abductors does not contribute to trunk and shoulder kinematics during throwing or the protocol may not have been sport-specific enough to alter kinematics.