Date of Award

1-1-2003

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Biomedical & Sport Science

Faculty

Faculty of Computing, Health and Science

First Advisor

Associate Professor Barry Gibson

Second Advisor

Associate Professor Helen Parker

Abstract

This research consists of two studies. The purpose was to investigate the effects of slow and fast music tempo on interjoint co-ordination variability in an aerobic stepping task. The 'step knee-up' task is a cyclical whole body movement performed on the step platform. The exercise consisted of a few repetitive cycles. A cycle was defined by eight counts, four counts for the left leg pattern and four for the right leg as follows: The first half of the cycle was counted: I. Step up with the left foot onto the 20-cm step platform, 2. Flex the right hip to bring the right knee up; 3. Step down to the floor with the right foot and, 4.Tap once with the left foot on the floor near the right foot. The second half of the cycle consisted of the following four counts: I. Step up onto the platform with the right foot; 2. Flex the left hip to bring the left knee up. 3. Step down to the floor with the left foot and, 4. Tap once with the right foot on the floor near the right foot. The participants were instructed to move both arms simultaneously forward and backward so that the limbs would perform in-phase movement, which is opposite to the natural anti-phase arm movements that accompanies walking and stepping activities. This pattern of the arm movements has been defined as a proposed pattern or the 'to-be-learned' pattern. In particular, the research examined to what extent unskilled and skilled participants would adjust their movement co-ordination to cope with changes in performance conditions in attempting to achieve the criterion task. In the first study, these effects were observed in novices and experts, while the effects of the fast tempo training on intrinsic dynamics (self-paced condition) were considered in the second study. Both studies were based on the Dynamic Systems Theory. The environmental factor, which was considered as the control parameter affecting performance in both studies, was the music tempo. In the first study interjoint co-ordination responses were analysed in terms of a version of the Haken, Kelso and Bunz's (HKB) modal that considers detuning or frequency competition terms. Six novice and six expert females participated in the experiment performing a 'step-knee-up', a whole body rhythmical task, under different music tempos. They were tested at a slow tempo at 48 beat/min and at a fast tempo of 144 beat/min. Two hypotheses were proposed. Firstly, it was hypothesised that discrete relative phase variability of inter-joints co-ordination would be higher.at the fast tempo then at the slow tempo in both, novices and experts. It was further hypothesised that, in order to cope with changes in performance conditions and still achieve the criterion task, novices would demonstrate higher variability than experts at both the slow and fast tempo. Results showed that interjoint co-ordination in experts was more consistent (less variable) at both the slow and fast tempo compared to novices, in all couplings expect in the left leg. Furthermore, follow-up tests revealed that Tempo and Side effects in novices were not significant. In experts, however significant Side effect was found in shoulder joint coupling and hip-knee joint coupling. Higher variability was found in left leg interjoint coupling between hip and knee joints at both tempos, compared to the right leg. In shoulders joint coupling, however, higher variability was found only in the slow tempo for the right side observation of the L Shoulder-R Shoulder movement. Finally, it was observed that the initially specified arm movement direction (iso directional or in-phase movement) changed to anti-phase direction at fast tempo in novices. Therefore, in novices, in-phase arm movements were more sensitive to fast tempo perturbations compared to anti-phase. While these results may be in contrast to Haken, Kelso and Bunz's model predictions they are partly supported by Whittal, Forester and Song's (1999) findings. In the second study, whether practising the task under the fast music tempo would affect the interjoint co-ordination stability at the preferred tempo performance (without the music) was investigated. It was hypothesised that, after the training under the fast music tempo interjoint coupling variability at the preferred tempo would decrease. The hypothesis was partly accepted as variability decreased in the self- paced condition after training only in shoulder-shoulder interjoint couplings compared to the self-paced condition before training. Results in the second study were discussed in relation to Shaner and Kelso's (1988) dynamical theory of environmental function and motor learning transfer principles. It was found that training under the fast tempo did not significantly affect overall performance at self-paced and fast tempos. However, different changes in interjoint co-ordination strength were observed in different couplings before and after training as the function of (the left or right) body side. It was concluded that interjoint co-ordination flexibility is highly specific to the interaction between the task, body side, performance condition and skill level. Finally it was suggested that an individual approach to the analysis of variability in co-ordination dynamics in skilled and unskilled performance and learning be considered.

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