Effect of external wrist weights on maximal countermovement vertical jump height in Loughborough University Sports Technology students.

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Effect of external wrist weights on maximal countermovement vertical jump height in Loughborough University Sports Technology students.

Abstract

        The aim of this study was to investigate the effect of external wrist weights on maximal countermovement vertical jump height. Data was collected from a group of eight Loughborough University students, who each performed three sets of jumps on a Kistler Quattro Jump platform with a variety of wrist weights. Though there were individual differences between subjects in the results, generally higher jumps were achieved when using external wrist weights, leading us to the conclusion that external weights on the wrists enhance performance, even if this is not the case when weights are attached to different body landmarks.

Introduction

        Vertical jumping is a simple plyometric activity common to many different sports and tasks such as vertical jumps, hops, and/or bounding movements are often used to increase explosiveness and strength of the lower extremities (Ebben, 2005). Plyometric exercise uses the stretch-shorten cycle to train muscles to do more work in less time.  In plyometric activities, muscles rapidly switch from an eccentric action to a concentric contraction, essentially leaving no time for the muscle to relax. Stored elastic energy in the muscle and the stretch reflex summate to permit the muscle to create greater force (McNeely, 2005). Experimental studies have investigated the anthropometric factors affecting vertical jump height (Wyon et al, 2007), the kinematics and kinetics of jumping (Schenau, 1985) and the effects of neuromuscular training on vertical jump height (Gerritsen, 2000). Computer simulation models have also been used to further investigate jumping, for example the effect of initial jumping posture on maximal vertical jump height (Selbie, 1996).

        This study investigates the effect of external weight on maximal countermovement vertical jump height. There is currently little knowledge in this area however there has been one study to date, investigating work and power production in the vertical jump under various loads fixed to the upper body or ankles (C. Corwin, 1998). A weighted vest was utilized to increase upper body mass in steps from 0 to 50 lbs in five skilled male jumpers. The subjects then performed a series of maximum effort non-countermovement jumps from a standardized starting position. After the weighted vest trials, ankle weights were used to increase the mass of the lower body.  The study reported that jump heights decreased as the load on the body increased for both vest and ankle weight conditions. The usefulness of the study is limited, since it was applied to only five, skilled subjects, and only tested two body sites. Therefore the external validity is low, as we have no evidence that the conclusions can be applied to the healthy population. We can also question the internal validity, since there are only five subjects; it is difficult to say whether the relationship between the weights and jump height was a causal relationship. The aim of this study is to add to our understanding in this area, by investigating the effect of wrist weights on maximal countermovement vertical jump height. The results from Corwin’s investigation lead us to hypothesize that increasing wrist weights will reduce maximal countermovement vertical jump height.

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Methods

        Eight Loughborough University students, (height 1.795 + 0.095m, mass 71.2 + 16.8kg) performed a series of countermovement vertical jumps with maximal voluntary effort on a Kistler Quattro Jump platform. Each subject performed three sets of three individual jumps, and was exposed to all treatment levels, i.e. no wrist weights (baseline measurement), 1.5kg attached to wrists (0.75kg each) and 3kg (1.5kg each) attached to each wrist. To minimise the impact on the experiment of order effects, counterbalancing was used to randomise the order of treatments. Though the subjects were obviously aware when they were jumping with no external weights, they were not ...

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