1. FORTUNA SCIENTES IUVAT
Correlation Between Work Absorbed, Peak Torque Decrement and Exercise-Induced Muscle Damage
D. Chapman, M. Newton, K. Nosaka, Z. Zainuddin, G. Morgan, A. Guilfoyle and P. Sacco (Sponsor: A. Morton, FACSM)
School of Biomedical and Sports Science, Edith Cowan University, Western Australia
Sports Science
INTRODUCTION
Various exercise protocols have been used to elicit exercise-induced muscle damage (EIMD)
Common non invasive measures of EIMD include loss of isometric and dynamic strength, raised serum creatine kinase (CK), reduced relaxed arm angle (RANG), range of motion (ROM) and muscle soreness (SOR)
EIMD is influenced by contraction type and intensity but the relationship between changes in muscle function associated with an exercise protocol and the extent of subsequent EIMD is unclear
RESEARCH QUESTION
Do changes in dynamic strength and or the work absorbed during eccentric exercise correlate with common indicators of EIMD?
Table 1. Pearson (2-tailed) bivariate correlation matrix of the dependent variables and outcome variables
Rsq = 0·2017
Rsq = 0·3103
Rsq = 0·0658
Rsq = 0·1488
Rsq = 0·0350
Table 2. Standardised coefficients for all outcome variables
Rsq = 0·0765
Rsq = 0·0155
Rsq = 0·0035
Figure 3. Scatterplot graphs of Pt change, CON, ISO 90, ISO150, RANG, ROM, CK, SOR against the change in WkA
METHODS
Twenty four physically active males (mean 31±7yrs) participated
60 maximal voluntary eccentric contractions of the elbow flexors (90°·sec-1) using a Cybex 6000 isokinetic dynamometer were used to induce EIMD
Exercise parameters measured were change in work absorbed (WkA) and change in peak torque (Pt) over exercise (expressed as a proportion of max)
Criterion measures were: changes in concentric strength at 90°·sec-1 (CON), and isometric strength at 90 and 150 degrees of elbow flexion (ISO90 and ISO150 respectively), relaxed arm angle (RANG), palpated SOR, ROM and serum CK.
Measurements were made pre- (-2 days) and daily for 7 days post-exercise.
DATA ANALYSIS
The largest change in the 7 days post-exercise for each criterion score was used for analysis (strength measures were normalised to baseline). A Pearson (2-tailed) bivariate correlation was used to indicate interactions between predictor variables (WkA and Pt) and the outcome variables (CON, ISO90, ISO150, RANG,ROM, SOR and CK), followed by linear regressions.
RESULTS
WkA had a significant positive correlation with CON (r=0.557; p<0.01) and weak positive correlations with ISO90 and ISO150 (r=0.257; r=0.386, n.s.).
In contrast, a weak negative correlation was found between WkA and ROM (r=-0.277).
Pt showed weak positive correlations with CON (r=0.486), ISO90 (r=0.340), ISO150 (r=0.355) and CK (r=0.293), but negative correlations with RANG (r=-0.232) and ROM (r=-0.339).
There were no correlations between WkA and CK or RANG; SOR did not correlate with either predictor
CONCLUSIONS
Neither exercise variable showed a strong correlation with common indicators of muscle damage, with the exception of WkA and CON
Observed changes in muscle function during eccentric exercise are not good predictors of subsequent responses in terms of the common indicators of EIMD
Decreases in muscle function are likely to represent factors associated with both neuromuscular fatigue and disruption to the excitation-contraction uncoupling and contractile elements associated with eccentric contractions