Improving single-legged-squat performance: Comparing 2 training methods with potential implications for injury prevention

Abstract

Context: Poor dynamic limb alignment during loading tasks has links to the development of knee injuries, including patellofemoral pain and anterior cruciate ligament injury. Therefore, modalities to improve limb alignment during loading tasks are thought to reduce loading through these structures and potentially prevent injury. Objective: To compare hip-strengthening and skill-acquisition training to examine if they can improve lower limb biomechanics, potentially preventing injury, and to examine whether changes demonstrated can be maintained after 6 weeks of no practice. Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants: A total of 19 recreationally active individuals volunteered, and 17 (9 women: Age = 27.9 ± 3.1 years, height = 165.4 ± 8.4 cm, mass = 60.5 ± 9.2 kg; 8 men: Age = 30.4 ± 6.4 years, height = 181.4 ± 7.1 cm, mass = 69.8 ± 15.2 kg) completed the study. Nine participants were allocated to a hip-strengthening program; 8, to a skill-acquisition program. Intervention(s): Participants performed a 6-week training program of either hip strengthening (n = 9) or skill acquisition (n = 8) 3 times per week. Main Outcome Measure(s): Measurements of clam-exercise strength, hip-abduction strength, frontal-plane projection angle, hip-adduction angle, and a qualitative score were taken at baseline, 6 weeks, and 12 weeks. Results: We observed improvements in frontal-plane projection angle (strength: T8=5.344, P=.001; skill: T7=4.393, P= .003), hip-adduction angle (strength: T8=3.597, P=.007; skill: T7 =4.722, P = .002), and qualitative score (strength: T8 = 3.900, P = .005; skill: T7 = 8.283, P < .001) postintervention, which were retained at the 12-week retest in both groups. Conclusions: A 6-week intervention of either hip-strengthening or skill-acquisition training improved lower limb biomechanics. The changes in biomechanics after skill training were retained at 12 weeks, suggesting a change in motor patterning that could be favorable to longer-term injury prevention.