Abstract
Previous research has demonstrated large amounts of inter-subject variability in downward (unweighting & braking) phase strategies in the countermovement jump (CMJ). The purpose of this study was to characterize downward phase strategies and associated temporal, kinematic and kinetic CMJ variables. One hundred and seventy-eight NBA (National Basketball Association) players (23.6 ± 3.7 years, 200.3 ± 8.0 cm; 99.4 ± 11.7 kg; CMJ height 68.7 ± 7.4 cm) performed three maximal CMJs. Force plate and 3D motion capture data were integrated to obtain kinematic and kinetic outputs. Afterwards, athletes were split into clusters based on downward phase characteristics (k-means cluster analysis). Lower limb joint angular displacement (i.e., delta flexion) explained the highest portion of point variability (89.3%), and three clusters were recommended (Ball Hall Index). Delta flexion was significantly different between clusters and players were characterized as “stiff flexors”, “hyper flexors”, or “hip flexors”. There were no significant differences in jump height between clusters (p > 0.05). Multiple regression analyses indicated that most of the jumping height variance was explained by the same four variables, (i.e., sum concentric relative force, knee extension velocity, knee extension acceleration, and height) regardless of the cluster (p < 0.05). However, each cluster had its own unique set of secondary predictor variables.
Highlights
The countermovement jump (CMJ) is an essential motor skill for a variety of sports including volleyball, soccer and basketball
Kinematic ICC values for each variable are listed from the hip, knee and ankle respectively: maximum joint flexion average (0.76, 0.90, 0.92), delta joint flexion (0.89, 0.80, 0.73), joint total range of motion (0.70, 0.88, 0.93), maximum joint flexion velocity (0.90, 0.92, 0.85), maximum joint flexion acceleration (0.86, 0.86, 0.76), maximum joint extension (0.92, 0.97, 0.98), maximum joint extension velocity (0.71, 0.91, 0.92), maximum joint extension acceleration (0.77, 0.79, 0.93)
Our main findings demonstrate that elite basketball players tend to fall into one of three downward phase movement strategies during the CMJ: stiff flexors, hyper flexors, and hip flexors
Summary
The countermovement jump (CMJ) is an essential motor skill for a variety of sports including volleyball, soccer and basketball. CMJ performance may provide a technical/tactical edge in both offensive and defensive actions (i.e., improving the probability of effective shots, rebounds and blocks) [1]. Due to its importance for a variety of sports, the CMJ is arguably the most common assessment implemented to measure lower body-ballistic performance [4]. Determining the variability in CMJ movement strategy may be more informative to coaches and athletes than jumping height per se, as the former may be associated with the ability of the players to perform specific technical and tactical skills. A defining feature of the CMJ is the downward phase performed prior to push off. According to McMahon et al, (2018) [5], the downward phase is composed of two components, unweighting and
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