Diagnostic measures to inform training prescription to alter countermovement jump strategy and improve performance

Abstract

Jumping is a fundamental demonstration of lower-body power across various sports, where the ability to generate maximal force quickly is crucial. Central to optimising vertical jumping performance is the stretch-shorten cycle (SSC), which involves the coupling of eccentric and concentric muscle actions with a rapid transition period. This cycle allows for the storage and release of elastic energy, enhancing force production in activities like the countermovement jump (CMJ). However, traditional measures of CMJ performance, such as jump height, often overlook the intricacies of how effective an athlete is at utilising the SSC mechanism.

Recent research emphasises the importance of analysing jump strategy – how an athlete moves their centre of mass (COM) during the CMJ – metrics derived from ground reaction force (GRF) data to understand and improve SSC utilisation. Despite this, challenges persist in assessing the variability and influence of these metrics on CMJ performance. Moreover, while lower-body strength is known to enhance CMJ performance, its relationship with jump strategy is less understood. This thesis aims to evaluate jump strategy metrics, investigate the influence of lower-body physical characteristics, and test the effects of a training intervention on jump strategy and CMJ performance.

The first study explores the variability and consistency of CMJ performance and jump strategy metrics, revealing the need for careful metric selection and interpretation. The second study examines the relationship between eccentric phase biomechanical parameters and CMJ performance, highlighting the importance and influence jump strategy has on optimising measures of CMJ performance. The third study investigates the influence of timing of peak GRF during the CMJ and maximal strength on jump strategy and CMJ performance, showing that stronger athletes achieve better performance outcomes and that the combination of increased strength and an optimised jump strategy produces the best CMJ performance outcomes. The final study of this thesis includes a six-week training intervention, which assess the impact of assisted CMJ exercises on jump strategy and performance. Despite changes in jump strategy metrics, no significant performance improvements were observed, suggesting that increased strength may be necessary to benefit from altered jump strategies.

This research provides insights into the complex interactions between jump strategy, SSC utilisation and lower-body strength, offering practical implications for optimising CMJ performance. The findings underscore the importance of holistic metric analysis and strength development in enhancing jump performance outcomes, paving the way for further research and refined training methodologies.