Hip Muscle Activity During a Functional Movement Assessment

CONTEXT: Neuromuscular control throughout functional movement is a risk factor for lower extremity injury. When implemented correctly, some preventive training programs (PTPs) decrease injury risk while focusing on strengthening the gluteus medius. Specific changes to faulty biomechanics are typically not accomplished. Understanding the causes of these risk factors, and techniques to manipulate them are crucial in injury prevention. OBJECTIVE: To evaluate potential differences in hip musculature activation, gluteus medius (GMed), gluteus maximus (GMax), and adductor magnus (ADD), during a jump-landing task between females with and without medial knee displacement (MKD). Additionally, to determine associations between hip muscle activation, vertical ground reaction force (vGRF), and movement control during a jump-landing task. STUDY DESIGN: Cross-Sectional Study. SETTING: Research laboratory. PARTICIPANTS: Thirty-one recreationally active female volunteers (age: 24 ± 5years; height: 167.3 ± 6.8cm; mass: 66.4 ± 10.0kg). MAIN OUTCOME MEASURES: Landings were scored for “errors” in technique using the Landing Error Scoring System (LESS). The activity (uV) of the gluteus medius (GMed), gluteus maximus (GMax), and adductor magnus (ADD) were recorded using surface electromyography (EMG); and, landing forces (% bodyweight) were recorded through force-plates. RESULTS: No significant differences observed between groups for age, mass, and peak vGRF. In the MKD group, negative correlations were seen between: GMed loading activation and vGRF (P=0.03; R2=-0.41); and, GMed:ADD preparatory activation and vGRF (P=0.04; R2=-0.36). In the control group, negative correlations were observed between GMed loading activation and LESS scores (P=0.02; R2=-0.28); GMed:ADD loading activation and LESS scores (P=0.01; R2=-0.32). A positive correlation was observed between GMed and GMax loading activation (P=0.01; R2=0.30). CONCLUSIONS: Individuals with MKD decrease their vGRF through higher activation of ADD as compared to their gluteus muscles. PTPs and rehabilitation efforts may be more effective with reducing MKD if GMax muscle activity is encouraged instead of ADD