Date of Award

2011

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Exercise, Biomedical and health Sciences

Faculty

Computing, Health and Science

First Advisor

Prof. Kazunori Nosaka

Second Advisor

Dr. Michael Newt

Abstract

It is well known that maximal eccentric exercise induces muscle damage, especially when it is performed for the first time. However, muscle damage is attenuated in subsequent bouts of the same or similar exercise, which is known as the repeated bout effect. One of the factors affecting the magnitude of muscle damage and the repeated bout effect is the number of eccentric contractions; however, it is unknown if different set-repetition configurations with the same number of eccentric contractions would result in different magnitudes of muscle damage and adaptation. This study investigated changes in muscle strength, range of motion (ROM), muscle cross sectional area (CSA), muscle soreness and plasma creatine kinase (CK) activity following an initial bout of maximal eccentric contractions with the same total number of contractions but different set-repetition configurations (e.g. 3 sets of 10 reps vs. 10 sets of 3 reps) and a second bout (20 sets of 3 repetitions) separated by four weeks. Since the present study was the first to use the ultrasound extended field of view (EFOV) technique to quantify bicep brachii CSA for an indication of muscle swelling, the reliability and validity of the technique were assessed in a separate study using 6 men (27.5 ± 1.9 y). In the main study, 10 non-resistance trained men (26.1 ± 4.1 y) performed two bouts of eccentric exercise of the elbow flexors for each arm (4 bouts in total). One arm performed 3 sets of 10 maximal eccentric contractions (3x10) followed 4 weeks later by 20 sets of 3 maximal eccentric contractions (20x3). The contralateral arm performed 10 sets of 3 maximal eccentric contractions (10x3) followed 4 weeks later by 20x3. The order of the exercise (3x10, 10x3) and the use of arm (dominant, non-dominant) were counterbalanced amongst subjects. Changes in the criterion measures over time and peak torque were compared among the initial bouts (3x10 vs. 10x3) and the repeated bouts (20x3 vs. 20x3) by a factorial repeatedmeasures analysis of variance (ANOVA) with two factors. Significance level was set at P<0.05 for all statistical analyses. In the study to investigate the validity against magnetic resonance imaging (MRI) and test-retest reliability, the results showed that EFOV was valid to measure biceps brachii CSA and could detect approximately 1% change in the CSA reliably. In the main study, the torque produced over 30 eccentric contractions was similar between 3x10 and 10x3, and the changes in torque during both 20x3 exercises were similar between arms. Maximal voluntary contraction strength, ROM, biceps brachii CSA, muscle soreness and plasma CK activity changed significantly after the first bouts without significant differences between 3x10 and 10x3, and changes in the measures following 20x3 were similar between arms. No significant differences in the changes of the criterion measures were evident between bouts. These results showed that the set-repetition configuration had little effect on muscle damage, which was likely to be due to similar peak torques produced during exercise between the 3x10 and 10x3 bouts. The repeated bout effect was similar between arms, suggesting that the set-repetition configuration in the first bouts did not affect the second bout. The similar changes in criterion measures between the first and second bouts showed that the repeated bout effect was attenuated by increasing the number of contractions. It is concluded that the number of contractions rather than the set-repetition configuration affects the magnitude of muscle damage and repeated bout effect.

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