Associations Between Body Composition Measures and Quadriceps Electromyography Amplitude

Electromyography (EMG) is a common tool utilized to measure the electrical activity of muscles. Electrical signals are required to facilitate muscle contraction, and EMG is often used to evaluate neuromuscular function in pathological populations. However, EMG amplitudes may be affected by measures of body composition since electrodes are typically placed on the surface of the skin, thus muscle electrical activity must pass through subcutaneous fat to be recorded. The purpose of this study was to examine the effect of body composition on EMG signal strength. Ten college-aged participants (aged 21-22) had body composition measured via Bioelectrical Impedance Analysis (BIA) followed by an assessment of quadriceps vastus lateralis (VL) and vastus medialis (VM) EMG amplitude during a maximal isometric knee extension task. Pearson correlation coefficients were utilized to evaluate the relationships between body composition measures and EMG amplitude. Findings revealed a significant inverse correlation between maximal EMG amplitude and body weight for the right limb VL (r = -0.881, P = 0.002) and VM (r = -0.723, P =0.028) and between right limb VL and Body Mass Index [BMI] (r = -0.744, P = 0.021). There were no significant correlations between EMG amplitude and specific measures of body fat (P = 0.212 – 6.81). These findings indicate that body weight and BMI may diminish EMG signals, possibly confounding muscle activation interpretation. Future studies should consider body composition as a variable in EMG-based research to improve measurement accuracy.