BACKGROUND & OBJECTIVE
Single leg hops are a recommended performance measure for determining readiness to return to sport (RTS) and have been shown to predict RTS after anterior cruciate ligament reconstruction (ACLR) . Prior studies have established a correlation between strength and hop performance, but few studies have looked at plyometric characteristics such as amortization time and reactive strength index (RSI) in determining single leg hop performance in individuals with ACLR. The purpose of this study was to assess the association of isometric knee extension strength characteristics and plyometric characteristics measured during a single-leg drop landing, with single-leg hop performance in individuals with ACLR.
Design: Cross-sectional study Participants: aged 18-40 years old, unilateral ACLR (8 participants had more than one ACLR done on the same knee), cleared by a medical professional for unrestricted physical activity Assessments: Data collection occurred over two sessions:
- Plyometric assessment: Lower extremity mechanics were assessed with the single leg vertical drop jump (SLVDJ) by a ten-camera Vicon Motion Analysis System and force plate. RSI, jump height, and amortization time were assessed. Hop performance was measured with the triple single leg hop (TSLH) and single leg hop (SLH) for distance in the same session.
- Strength assessment (average 8 days later): Knee extension maximal voluntary isometric contraction (MVIC) was assessed with a Biodex Dynamometer. Peak torque and rate of torque development (RTD) were also assessed.
Participants: 54 participants (mean age 22.94 ± 5.0 years, 61% females) were included. Participants ranged from 37.6 ± 23.7 months after ACLR.