Analyzing How Skinfold Thickness Affects Log-Transformed EMG Amplitude–Power Output Metrics

Abstract

Background: The purpose of this study was to determine whether accounting for skinfold thickness would reduce the variability observed on a subject-by-subject basis for the y-intercept and slope terms derived from the log-transformed EMG amplitude–power output relationship. We hypothesized that using skinfold thickness as a covariate would reduce the subject-by-subject variability in the y-intercept and slope terms and, therefore, indicate potential mean differences between muscle groups. Methods: Subjects had the skinfold from their three superficial quadriceps femoris muscles measured and then EMG electrodes placed over the three muscles. Thereafter, each subject performed an incremental single-leg knee-extensor ergometer exercise test to voluntary exhaustion. Results: The results indicated that using skinfold thickness as a covariate did not change the statistical outcome when comparing the mean values for the y-intercept or slope terms across the three superficial quadriceps femoris muscles. Conclusion: These findings suggest that there may be other factors that are influencing the subject-by-subject variability for the y-intercept and slope terms, respectively.