Date of Award

2014

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Exercise and Health Sciences

Faculty

Health, Engineering and Science

First Advisor

Associate Professor Anthony Blazevich

Second Advisor

Professor Ken Nosaka

Abstract

The mechanisms underpinning the immediate torque loss induced by acute, static muscle stretching are still not clear. The current research was designed to examine the neuromuscular factors influencing this torque loss. In Study 1, the contributions of central versus peripheral factors to the stretch-induced torque loss were investigated. Measures of central drive, including the EMG amplitude normalised to the muscle compound action potential amplitude (EMG:M), percent voluntary activation (%VA) and first volitional wave amplitude (V:M), and measures of peripheral function, including the twitch peak torque and 20:80 Hz tetanic torque ratio were made before, and immediately and 15 min after a 5-min continuous plantar flexor stretch. There was a 15.7% (p

Alternatively, intermittent (i.e. repeated) stretching commonly performed by athlete and clinical populations causes cycles of ischaemia-reperfusion, increasing the likelihood of contractile failure. Therefore, Study 2 was designed to determine whether intermittent stretch might cause greater torque loss when compared to continuous stretch, and to quantify the potentially greater peripheral effect. The main findings were that intermittent stretch induced a greater torque loss (-23.8%; p

Central drive failure can clearly be of spinal origin, and it is reasonable to speculate that muscle stretch might affect the afferent-mediated motor neurone facilitatory system. Thus, in Study 3 a vibration-stimulation protocol (vib+stim) was used to elicit reflexmediated muscular contractions during two experiments. In Experiment 1, vib+stim was imposed with the ankle joint plantar flexed (+10°), neutral (0°) and dorsiflexed (-10°). Torque and EMG amplitudes during vibration and during the self-sustained torque period after vib+stim were greater in dorsiflexion, providing method validation. In Experiment 2, vib+stim was imposed twice before (Control) and immediately, 5, 10 and 15 min after a 5-min intermittent stretch protocol. Torque and EMG amplitude were depressed immediately after stretching during both vibration (-60% and –41%, respectively; p

Share

 
COinS