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Abstract
The purpose of this study was to relate the shape of countermovement jump (CMJ) vertical ground reaction force waveforms to discrete parameters and determine if waveform shape could enhance CMJ analysis. Vertical ground reaction forces during CMJs were collected for 394 male and female collegiate athletes competing at the National Collegiate Athletic Association (NCAA) Division 1 and National Association of Intercollegiate Athletics (NAIA) levels. Jump parameters were calculated for each athlete and principal component analysis (PCA) was performed on normalized force-time waveforms consisting of the eccentric braking and concentric phases. A K-means clustering of PCA scores placed athletes into three groups based on their waveform shape. The overall average waveforms of all athletes in each cluster produced three distinct vertical ground reaction force waveform patterns. There were significant differences across clusters for all calculated jump parameters. Athletes with a rounded single hump shape jumped highest and quickest. Athletes with a plateau at the transition between the eccentric braking and concentric phase (amortization) followed by a peak in force near the end of the concentric phase had the lowest jump height and slowest jump time. Analysis of force-time waveform shape can identify differences in CMJ strategies in collegiate athletes.
Highlights
The countermovement jump (CMJ) is a popular assessment of athletic performance with numerous parameters proposed to quantify important aspects of the force–time curves generated during a CMJ.debate continues regarding which of these parameters provides the best overall assessment of athletic performance [1,2,3,4,5,6]
Explosive jumpers are characterized by the ability to jump high in a short amount of time and can be identified by the reactive strength index modified (RSImod) parameter [8,9,10], which is the ratio of jump height over jump time
A K-means clustering was used to cluster athletes based on their principal component analysis (PCA) scores and CMJ parameters were compared between athletes in each cluster
Summary
The countermovement jump (CMJ) is a popular assessment of athletic performance with numerous parameters proposed to quantify important aspects of the force–time curves generated during a CMJ. Debate continues regarding which of these parameters provides the best overall assessment of athletic performance [1,2,3,4,5,6]. Discrete parameters derived from force–time data (e.g., peak force) reduce the dimensionality of the measured waveform [7], facilitating analysis, but important information on how athletes generate force during the jump cycle may be lost. It is invaluable for the practitioner to understand how an athlete applies force and to be able to relate that force application to performance. How the athlete applies force throughout the movement may be of importance for training exercise. Explosive jumpers are characterized by the ability to jump high in a short amount of time and can be identified by the reactive strength index modified (RSImod) parameter [8,9,10], which is the ratio of jump height over jump time
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