Hip moment and knee power eccentric utilisation ratios determine lower-extremity stretch-shortening cycle performance

The eccentric utilisation ratio (EUR) is calculated as the ratio between countermovement jump (CMJ) and squat jump (SJ) heights, and is an indicator of lower-extremity stretch-shortening cycle (SSC) performance in athletes. Joint-based EUR can also be calculated but have never been reported. The purpose of this study was to investigate whether jump height-based (JH-based) EUR can be predicted by joint-specific EUR. Nine NCAA Division I college athletes (age: 21 ± 1 year, height: 1.75 ± 0.15 m, mass: 71 ± 20 kg) performed three SJ and CMJ. During all jumps, kinematic and kinetic data were obtained and used to calculate hip, knee and ankle net joint moments (NJM) and net joint powers (NJP). JH was calculated from pelvis marker data. EUR (CMJ/SJ [unitless]) were calculated for JH, NJM, and NJP. JH-EUR was 1.11 ± 0.70. NJM-EUR were 1.07 ± 0.17, 1.17 ± 0.25, and 1.07 ± 0.18 for the hip, knee and ankle joint, respectively. NJP-EUR were 1.41 ± 0.12, 1.26 ± 0.28 and 1.06 ± 0.11 for the hip, knee and ankle joint, respectively. Regularised regression showed that Hip-NJM-EUR, Knee-NJP-EUR and Ankle-NJM-EUR were able to predict 83% of the variance in JH-EUR, which suggests that the enhancement of lower-extremity SSC performance during CMJ arises from a combination of these parameters.