Date of Award

1-1-2008

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Exercise, Biomedical and Health Sciences

Faculty

Faculty of Computing, Health and Science

First Supervisor

Associate Professor Kazunori Nosaka

Second Supervisor

Dr Mike McGuigan,

Third Supervisor

Dr Mike Newton

Abstract

Lengthening contraction velocity appears to be one of the factors affecting the magnitude of muscle damage, however limited human studies have investigated this issue. The purpose of this thesis was to clarify the effect of lengthening contraction velocity on changes in indirect markers of muscle damage after maximal voluntary lengthening exercise of the elbow flexors. This thesis incorporates five individual studies that have been published or submitted for publication in peer review journals.

The first study investigated the hypothesis that the variability of changes in indirect markers of muscle damage would be explained by work performed and/or torque generated during lengthening contraction exercise. Fifty-three subjects performed 60 maximal lengthening contractions of the elbow flexors through a range of movement from 60° to 180° of elbow flexion at a constant angular velocity of 90°·s -1 • Pearson's correlation coefficient was used to examine relationships between exercise parameters (total work, change in total work, torque produced during exercise, change in peak torque) and markers of muscle damage (maximal voluntary isometric contraction torque, range of motion, plasma creatine kinase activity and muscle soreness) were measured before, immediately after, and 24 - 96 hours after exercise. The analysis revealed that a large inter-subject variability was evident for both work and torque during exercise, and for changes in all markers of muscle damage. Contrary to the hypothesis, total work (normalised for individual pre-exercise MVC) absorbed during the exercise did not correlate significantly with any markers of muscle damage, with the exception of MVC (r = 0.3). Total work absorbed and changes in total work showed higher correlations with some markers, but nor-values exceeded 0.4. Normalised exercise torque and the changes in peak torque during exercise were not correlated with changes in MVC, nor other markers. The findings from this investigation suggested that the large inter-subject variability in responses to maximal voluntary lengthening exercise is not associated with work performed or torque generated during lengthening exercise.

The aim of the second study was to verify the lengthening torque-velocity relationship of human elbow flexors by considering whether muscle damage induced in maximal lengthening torque measurements influences the relationship. Twenty subjects were tested twice, separated by seven days, for maximal isometric strength at 90° of elbow flexion and maximal dynamic strength during lengthening contractions at velocities of 30°·s-1 followed by 90°, 150°, 210°·s-1 , and a repeated 30°·s-1 using a range of movement from 60° to 140°, where 180° was considered full extension. Assessment of maximal isometric strength preceded each lengthening contraction to assess the effects of muscle damage and/or fatigue on the measures. The difference in lengthening contraction strength at 30°·s-1 between the first and second attempts was used to adjust the torque values. The reliability of the measurements was supported by high intra-class correlation coefficients (0.96 - 0.99) and low coefficient of variation (6.3 - 9.1 %). Peak lengthening contraction strength across all velocities was significantly greater than maximal isometric strength (14 - 16%), but no significant differences were evident within velocities. The second lengthening contraction performed at 30°·s-1 was significantly lower (-10%) than the first, and maximal isometric strength decreased significantly over the measurements (-10%). Following adjustment, no significant differences in maximal dynamic lengthening torque among velocities were evident. It was concluded that lengthening contraction torque is approximately 15% higher than isometric torque without an influence of angular velocity for the elbow flexors in an untrained population.

The purpose of the third study was to investigate the effect of lengthening contraction velocity on muscle damage. Sixteen men were placed into two groups performing either 30 (n = 8) or 210 (n = 8) maximal lengthening contractions of the elbow flexors on an isokinetic dynamometer. Dominant and non-dominant arms were randomly assigned for a slow (S: 30°·s-1 ) or a fast (F: 210°·s-1 ) velocity exercise separated by 14 days. Maximal voluntary strength of isometric contractions (iMVC) and isokinetic concentric contractions ( cMVC), range of motion (ROM), upper arm circumference, muscle soreness and serum creatine kinase (CK) activity were measured before, immediately after, and 1 - 120 hours following exercise. Changes in these measures over time were compared by a two-way repeated measures ANOV A to examine the effect of velocity in the same number of contractions (S30 vs F30; S210 vs F210) or the effect of contraction number at the same velocity (S30 vs S21 O; F30 vs F210). A significant interaction effect was evident only for iMVC (90° P = 0.020 and 150° P = 0.033) between S30 and F30, but for iMVC (90° P = 0.040 and 150° P= 0.000), cMVC (150°·s-1 P= 0.042), ROM (P= 0.001) and CK (P = 0.000) between S210 and F210. Changes in most of the measures were significantly smaller after 30 (S30 and F30) than 210 contractions (S210 and F210). These results suggest that the effect of contraction velocity on the magnitude of muscle damage following 30 contractions is minor; however, when 210 lengthening contractions were performed, the effect of contraction velocity became conspicuous. It is concluded that fast velocity lengthening contractions are likely to induce greater muscle damage than slow velocity contractions; however, muscle fatigue appears to be a confounding factor for the velocity effect.

The fourth study tested the hypothesis that the first bout of exercise consisting of slow velocity (30°·s- 1 ) maximal lengthening contractions would not confer protection against a subsequent bout of exercise consisting of fast velocity (210°·s- 1 ) lengthening contractions. Eighteen men (26.3 ± 4.2 yrs) were randomly placed into two groups; repeated bout group (n = 10) and control group (n = 8). The repeated bout group performed two bouts of exercise consisting of 210 (3 5 sets of 6) maximal lengthening contractions of the elbow flexors separated by 14 days using their nondominant arm at a velocity of 30°·s-1 for the first bout and 210°·s-1 for the second bout. The control group performed the fast velocity bout only. Changes in maximal isometric strength, range of motion, upper arm circumference, muscle thickness, muscle soreness, serum creatine kinase and lactate dehydrogenase activities were measured before, immediately after, and 24 - 96 hours after exercise. Changes in the measures over time after the fast velocity exercise were compared between groups by a two-way repeated measure ANOV A. For the repeated bout group, changes in the measures were compared between bouts by a two-way repeated measure ANOV A. The repeated bout group showed significantly smaller changes or faster recovery of all criterion measures except for muscle soreness after the fast velocity exercise compared with the control group. A significant difference in the changes in the criterion measures between the slow and fast velocity bouts of the repeated bout group was evident only for range of motion. These results suggest that a bout of slow velocity lengthening contractions confers protection against muscle damage induced by fast velocity lengthening contractions, although the magnitude of protective effect conferred by the slow velocity exercise is not strong.

The final study investigated the hypothesis that muscle damage induced by fast velocity lengthening contractions would be greater for old than young men. Ten old ( 64 ± 4 yrs) and 10 young (25 ± 6 yrs) men performed 5 sets of 6 maximal voluntary lengthening contractions, through a range of movement from 60° to 180° at the angular velocity of 210°·s-1 • Changes in maximal isometric strength, optimum angle, elbow joint range of motion (ROM), upper arm circumference, muscle thickness and echo intensity assessed by B-mode ultrasonography, muscle soreness, and serum CK and LDH activities before, 1, 24 - 96 hrs post exercise were compared between the young and old groups by a two-way repeated measure ANOV A. Prior to exercise no significant differences were observed between groups for criterion measures, and for the work performed during exercise. A significant group x time interaction effect was found for isometric strength and muscle soreness, with the old group showing significantly slower recovery of strength and less development of soreness compared with the young group. Changes in other measures were not significantly different between groups. The results of this study refuted the hypothesis that old men are more susceptible to muscle damage, but confirmed the previous studies reporting that recovery of muscle strength is slower for old than young individuals. The mechanical factors, work absorbed and torque developed during lengthening contractions were not related to the magnitude of muscle damage. In addition it was determined that the torque developed during voluntary lengthening contractions with increasing velocities did not differ significantly. These works were used to justify the major findings from these studies indicating that lengthening contraction velocity has a significant effect on the magnitude of muscle damage with fast velocity lengthening contractions resulting in significantly greater damage than slow velocity lengthening contractions. It was proposed that the results are indicative of a stress susceptible group of muscle fibres that may not be fibre type specific but consists of a greater proportion of type II muscle fibres.

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