The optimal load to maximise system power during a countermovement jump

  • Kym James Williams

    Student thesis: Doctoral Thesis


    The ability to express power is considered a fundamental determinant of sporting performance. Practitioners and sports scientists have therefore searched for training modalities and loads that optimise power production. Currently, there is contention regarding what load maximises power during explosive (multi-segmental) movements. Although discrepancies in measurement techniques confound interpretation, an inter-subject variation on the load that maximises power has also been observed between and within sports, leaving practitioners with little practical clarity. Therefore, this thesis seeks to describe the current practices employed to monitor and maximise power, while experimentally determining whether the observed variation in the load that maximises power can be explained by sporting background, differences in anthropometric qualities, or isolated joints contributions compared to whole body measures between several groups of highly trained athletes. This body of work will assist in the understanding and prescription of training loads that look to maximise power production in the field of strength and conditioning. To achieve the investigative aims, a survey was conducted to describe the current practices employed by national strength and conditioning coaches (Chapter 3). We observed practical ambiguity in analysis techniques and loads used to monitor and maximise power. Based on this finding, an examination of the measurement bias attributed to alternative analysis techniques were instigated (Chapter 4). The findings demonstrated that disparity in analysis techniques significantly influenced the accuracy, precision, inter-measurement agreement of force, velocity, and power values under different relative loads during a countermovement jump (CMJ). The demonstrated bias is attributed to alternative analysis procedures that could alter the shape of the load-power relationship compared to first principle measures obtained from a combined kinetic and kinematic approach. Implementing a combined kinetic and kinematic data collection and analysis approach as advocated in Chapter 4,the fifth chapter reports that system power (body mass + bar) is maximised across a number of relative loads between athletes during a CMJ. Interestingly, force-,velocity-,and power-load profiles were distinctly different between sports. By further deconstructing system power to the joint level (Chapter 6),sporting and athlete dependent differences in joint kinetics and kinematics were observed to influence the system load-power relationship. This finding was interpreted to be the result of undefined athlete-dependent traits manipulating the optimal balance in force and velocity at the joint and system level to account for individual characteristics. To understand the physical mechanism behind this variation in CMJ load-power profiles, Chapter 7 reports that alternative sporting and anthropometric characteristics alter the generation, contribution, and timing of joint and system power across a range of relative loads. Consequently, a mixture of athlete-dependent anthropometric and sporting related traits explained the inter-subject variance in the load maximising power during a CMJ. Therefore, the load that maximises power is athlete-dependent, and not a universal load as previously ascribed. This series of investigations found that the current practices employed to monitor power where disparate between practitioners, leading to alternative load-power profiles to be reported between measurement and analysis techniques. Furthermore, differences in sporting background and anthropometric traits will influence the contribution, timing and generation of power at a joint and system level. These difference in athlete dependent characteristics affects the shape of the load-power relationship, and therefore the load that maximises power between a group of highly trained athletes. Therefore, the load that maximises CMJ power is athlete-dependent, and not a universal load. Alternatively, a combination of training loads that target various neuromuscular or mechanical characteristics may be more advantageous in maximising system and joint power production compared to a universal load that may not constitute a sufficient trigger to improve the translation of power about the lower-body joints. This body of work highlights the diversity of human neuromuscular and mechanical behaviours that determines an athlete’s unique response to alternative training conditions. It is, therefore, a worthwhile contribution to the field of strength and conditioning, consolidating information on the use of the force-velocity and load-power relationship as it applies to the science of training athletes.
    Date of Award2017
    Original languageEnglish
    SupervisorNick Ball (Supervisor), Dale Chapman (Supervisor), Kevin Thompson (Supervisor), Elissa J. Phillips (Supervisor) & Julian V. Jones (Supervisor)

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