Title

Neuromuscular and biomechanical characteristics of change of direction and agility performance

Date of Award

2015

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Exercise and Health Sciences

Faculty

Faculty of Health, Engineering and Science

First Advisor

Dr Sophia Nimphius

Second Advisor

Professor Robert U Newton

Third Advisor

Dr Jeremy M Sheppard

Abstract

Study 1: The contribution of strength characteristics to change of direction and agility performance in female basketball athletes

Research has often examined the relationship between one or two measures of strength and change of direction (COD) ability, reporting inconsistent relationships to performance. These inconsistences may be the result of the strength assessment utilized and the assumption that one measure of strength can represent all “types” of strength required during a COD task. Therefore the purpose of this study was to determine the relationship between several lower body strength and power measures, COD, and agility performance. Twelve (n=12) female basketball athletes completed a maximal dynamic back squat, isometric mid-thigh pull, eccentric and concentric only back squat, and a counter-movement jump, followed by two COD tests (505 and T-Test) and a reactive agility test. Pearson product moment correlation and stepwise regression analysis were performed on all variables. The percentage contribution of each strength measure to an athlete’s total strength score was also determined. Our results demonstrated that both COD tests were significantly correlated to maximal dynamic, isometric, concentric and eccentric strength (r = -0.79 to -0.89), with eccentric strength identified as the sole predictor of COD performance. Agility performance did not correlate with any measure of strength (r = -0.08 to -0.36), while lower body power demonstrated no correlation to either agility or COD performance (r = -0.19 to -0.46). These findings demonstrate the importance of multiple strength components for COD ability, highlighting eccentric strength as a deterministic factor of COD performance. Coaches should aim to develop a well-rounded strength base in athletes; ensuring eccentric strength is developed as effectively as the often-emphasized concentric or overall dynamic strength capacity.

Study 2: Mechanical determinants of faster change of direction and agility performance in female basketball athletes

Change of direction (COD) and agility require the integration of multiple components to produce a faster performance. However, the mechanisms contributing to a faster performance without the confounding factor of athlete expertise or gender is currently unknown. Therefore, the purpose of this study was to assess body composition, strength and kinetic profile required for a faster COD and agility performance across multiple directional changes. Six faster and six slower (n=12) elite female basketball athletes completed a maximal dynamic back squat; eccentric and concentric only back squat; isometric mid-thigh pull; whole body scan to determine lean, fat and total mass; 505 COD test; T-Test; and a multidirectional agility test over in-ground force plates to obtain relevant kinetic measures. Group (faster and slower) by test (2x3) MANOVA’s with follow up ANOVA’s were conducted to examine differences between faster and slower groups and each COD and agility test (p ≤ 0.05). Faster athletes during the 505 COD test produced significantly greater vertical force (p = 0.002) and eccentric and isometric strength capacity (p = 0.001). Faster agility and T-Test athletes demonstrated significantly shorter contact times (p = 0.001), greater propulsive impulse (p = 0.02), isometric strength, and relative lean mass compared to slower athletes. Differences between faster athletes across each test appear to be attributed to the mechanical demands of the directional change, increasing force and impulse application as the degree of directional change increased. These findings indicate that different mechanical properties are required to produce a faster COD and agility performances, and the importance of a greater strength capacity to enable greater mechanical adjustment via force production and body control, during different directional changes.

Study 3: Neuromuscular strategies contributing to faster multidirectional agility performance

The aim of this study was to first determine differences in neuromuscular strategy between a faster and slower agility performance, and second compare differences in muscle activation strategy employed when performing two closely executed agility movements. Participants recruited from an elite female basketball team completed an ultrasound to determine quadriceps muscle-cross sectional area; reactive isometric mid-thigh pull to determine the rate of muscle activation, rate of force development, pre-motor time and motor time; and multidirectional agility tests completing two directional changes in response to a visual stimulus. Peak and average relative muscle activation of the rectus femoris, vastus medialis, vastus lateralis, biceps femoris, semitendinosus and gastrocnemius were measured 100 ms prior to heel strike (pre-heel strike) and across stance phase for both directional changes. Faster agility performance was characterized by greater pre-heel strike muscle activity and greater anterior muscle activation during stance phase resulting in greater hip and knee extension increasing propulsive impulse. Differences between directional changes appear to result from processing speed, where a greater delay in refractory times during the second directional change resulted in greater anterior muscle activation, decelerating the body whilst movement direction was determined

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