Work and peak torque during eccentric exercise do not predict changes in markers of muscle damage

Abstract

Objectives: Large inter-subject variability in responses to eccentric exercise has been reported. This study investigated the hypothesis that the variability of changes in indirect markers of exercise-induced muscle damage (EIMD) would be explained by work performed and/or torque generated during eccentric exercise. Methods: Subjects (n = 53) performed 60 maximal eccentric actions of the elbow flexors on an isokinetic dynamometer that forcibly extended the elbow joint from 60° to 180° at a constant velocity (90° s -1). Markers of EIMD included maximal voluntary isometric contraction torque at 90° elbow flexion (MVC), range of motion, plasma creatine kinase activity and muscle soreness. Measurements were taken 2 days before, immediately after and 1-4 days post-exercise. 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 EIMD. Results: Large inter-subject variability was evident for both work and torque during exercise, and changes in all markers of EIMD. Contrary to the hypothesis, total work (normalised for individual pre-exercise MVC) did not correlate significantly with any markers of EIMD, with the exception of MVC (r = 0.3). Total work performed and changes in total work showed higher correlations with some markers, but no r-values exceeded 0.4. Normalised exercise torque and the changes in peak torque during exercise were not correlated with changes in MVC, or other markers. Conclusion: These results suggest the large inter-subject variability in responses to eccentric exercise is not associated with work performed or torque generated during eccentric exercise.