Date of Award

2015

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Exercise and Health Science

Faculty

Faculty of Health, Engineering and Science

First Advisor

Dr Anthony Blazevich

Second Advisor

Dr Dale Chapman

Abstract

The purpose of this investigation was to determine the effect of 6 weeks of vertically- and horizontally-directed lower-body plyometric exercise with vertically versus horizontally biased ground force application, on 40-m sprint running time, vertical jumping height, body composition and gastrocnemius medialis (GM) muscle architecture. Male (n = 19) and female (n = 20) recreational athletes were recruited and stratified according to 40 m sprinting ability, then randomly allocated to one of two groups: horizontally-directed plyometric training (HT) and vertically-directed plyometric training (VT).

The groups performed the experimental procedures twice each week with the same number of total ground contacts, while maintaining their usual weekly training load. During training the subjects performed bounding exercises with maximum effort with either a horizontal or vertical directional bias, depending on the allocated group. Sprinting performance was undertaken on an indoor, sprung-cork running track with the times recorded using infra-red timing gates recording to the nearest 0.01s. Ground reaction forces (GRFs) were recorded using in-ground, multi-component, peizo-electric force platforms.

Changes in performance and muscle function were assessed during counter-movement jumps (CMJs), squat jumps (SJs), and depth jumps (DJs) from 0.20 m (reactive strength index (RSI-20)) and 0.40 m (RSI-40). Muscle fascicle length (FL) and angle pennation (AP) of the GM were assessed using ultrasonography, while dual-energy x-ray absorptiometry (DEXA) was used to determine body fat percentages (BF%) and composition of the shank of the subjects’ dominant legs (push-off leg during sprinting). Multivariate, repeated measures analyses of variance were used to determine differences between training groups and percentage of change scores were calculated for each variable. Both HT and VT presented statistically significant (p ≤ 0.05) with small-to-moderate standardised effect (d) improvements in 10-m (HT: d = 0.22; VT: d = 0.09), 20-m (HT: d = 0.20; VT: d = 0.15), 30-m (HT: d = 0.24; VT: d = 0.23) and 40-m (HT: d = 0.40; VT: d = 0.39) times, with no differences between the groups. No statistical change was seen for either experimental group at 5-m, however a small and trivial practical change was observed for HT (d = 0.20) and VT (d = 0.04) groups. Significant changes were observed for CMJ, SJ, RSI-20 and RSI-40 for both HT and VT groups, without a significant difference between groups. No significant or practical benefit in the change following training was observed for FL (HT: d = 0.02; VT: d = 0.05) or AP (HT: d = 0.04; VT: d = 0.08), with no between group significant differences. Following training significant changes in both experimental groups were observed for BF% (HT: d = 0.13; VT: d = 0.18) and total body mass (HT: d = 0.09; VT: d = 0.09), however there was no significant difference between groups.

The outcomes suggest that HT and VT were similarly effective at improving sprinting and vertical jumping performance, in recreational athletes. The observed outcomes support the use of either movement-specific training paradigms or kinetically dissimilar exercises for the purpose of improving sprinting performance, even though greater forces may be applied.

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