Author(s): PALAMARCUKAS, I., ZHU, T., KONG, P.W., Institution: NANYANG TECHNOLOGICAL UNIVERSITY, Country: SINGAPORE, Abstract-ID: 1362

INTRODUCTION:
Countermovement jump (CMJ) is an important motor skill in many sports and it is widely used as a test to measure athletic abilities. Whilst both the knee and hip joints have similar contributions during maximal CMJ (1), little is known about how knee and hip strength affects CMJ strategy. Tailoring CMJ biomechanics to be more aligned with the constraints of the sport (e.g., jumping with an upright torso when rebounding in basketball) could enhance performance. Additionally, modifying jumping strategy may help reduce injury in individuals with predisposition for certain joint injuries (e.g., patellar tendinopathy) by changing the distribution of load between joints. To our knowledge, previous research on how muscular strength affects CMJ strategy is either cross-sectional (2) and or focuses on a single joint (3). Therefore, this study aims to compare whether training of knee versus hip musculature has divergent effects on CMJ strategy.
METHODS:
Eleven participants with at least 1 year of resistance training experience (7 females, 8 males, 25.7 ± 5.2 years, 1.71 ± 0.08 m, 65.4 ± 7.7 kg) were randomly assigned into either knee (n = 8) or hip (n = 6) training group. The pre- and post-tests consisted of 2 sets of 3 repetitions maximal-effort CMJ with a 3D motion capture system and a force platform under the dominant leg. The training intervention comprised 12 sessions of 90°/s isokinetic eccentric-concentric knee or hip extensions performed for 6 sets of 6 repetitions. Differences between knee and hip groups following the training intervention were quantified using the interaction of group and time coefficient from a multilevel function on scalar linear regression (4). The coefficient was deemed statistically significant when the pairwise confidence interval did not cross 0.
RESULTS:
After 12 sessions of training, there was no significant improvement in jump height for either group. Relative to the hip group, the knee group significantly increased knee joint moment by 0.2 Nm/kg in the 50-82% of CMJ repetition as well as hip joint moment by 0.25 Nm/kg in the 40-65% of CMJ repetition. Additionally, compared to the hip group, the knee group improved knee joint power by 1.5 W/kg in the 65-85% on CMJ repetition with no significant changes for hip joint power.
CONCLUSION:
Isolated training of the knee or hip extensors have divergent effects on CMJ joint kinetics. Relative to hip extension training, knee training increased both knee and hip joint moment, but enhanced only knee joint power. This suggests that the knee joint is more responsive to single-joint strength training compared to the hip joint when bodyweight CMJ biomechanics are concerned. These findings have implications for investigating longitudinal determinants of CMJ motor strategy as well as individualising sports performance training.

1) Zhang et al., Sci Rep 2025
2) Spudic et al., Appl. Sci. 2025
3) Rajic et al., J. Hum. Kinet., 2020
4) Cui et al., J. Comput. Graph. Stat, 2022