Date of Award

2003

Degree Type

Thesis

Degree Name

Master of Science

School

School of Biomedical and Sport Science

Faculty

Faculty of Computing, Health and Science

First Advisor

Dr Paul Sacco

Second Advisor

Mike Newton

Abstract

Eccentric contractions, where a muscle is repeatedly lengthened while generating torque, result in decreased muscle function and muscle soreness. This study was designed to determine whether there was a difference in muscle response of the elbow flexors from untrained subjects (n = 12) between a bout of high intensity eccentric exercise at 30°•s-1 (LVE) compared to the equivalent at 210°•s-1 (HVE). Subjects performed 120 seconds of eccentric exercise of the elbow flexors using a Cybex 6000 Isokinetic Dynamometer. At 30°-s-1, a total of 30 repetitions were required whilst at 210°•s-1, 210 contractions were performed (at a 1:7 work/rest ratio). Both exercise bouts resulted in significant decrements in isometric and dynamic strength measures (p<0•01) with HYE resulting in significantly greater reductions and a longer recovery compared to LYE. HVE also showed larger (p<0•05) increases in serum CK than LYE and the time taken to return to baseline levels was longer. LYE had significantly (p<0•05) smaller changes in the circumference (CIR) of the upper arm as compared to HVE, mean peak increase in CIR after LYE was 04 cm (±0•1) and following HVE it was 0•8 cm (± 0•1) (SEM). Significant (p<0•05) levels of palpated, flexed and extended muscle soreness were experienced following both exercise conditions and the recovery time was extended for HVE. The two exercise conditions resulted in significant (p<0•05) reductions in subjects' ROM (LYE= 12° ± 4 and HVE = 23° ± 8) and relaxed arm angle (RANG) (LYE= 4° ± 1 and HYE = 110 ± 2) (mean ± SEM). Significant (p<0•05) differences were observed between groups and normal function had returned 168 hours following exercise for ROM and RANG. The most likely explanation for the findings is that a greater mechano-chemical strain is placed on fewer fibres in HVE as compared to LYE, despite similar peak torques. The site for where this increased strain occurs is not easily definable, but may possibly be the contractile protein titin or desmin or contractile structures such as costameres or sarcomeres.

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