Adipose tissue thickness does not affect the electromechanical delay

During voluntary contractions in humans, the subcutaneous tissues between surface electrodes and active motor units have been shown to attenuate surface electromyographic (EMG) signal amplitude. The purpose of this investigation was to examine the relationship between adipose tissue thickness and the electromechnical delay (EMD) during maximal voluntary contractions (MVCs). Thirty-two healthy women (mean  ±  SD age  =  21  ±  2 years; mass  =  60.7  ±  11.5 kg; height  =  161.7  ±  7.5 cm; dual-energy x-ray absorptiometry body-fat percentage  =  33.1  ±  9.9%) performed MVCs of the right leg extensors while bipolar surface EMG signals were detected from the vastus lateralis muscle. EMD was calculated as the time (ms) between EMG and torque onsets. B-mode ultrasonography was used to determine adipose tissue thickness over the same location of the vastus lateralis where the EMG sensor was placed. Partial correlation was used to examine the relationship between adipose tissue thickness and EMD while statistically removing the influence of peak torque, EMG amplitude, and vastus lateralis muscle thickness. The partial correlation demonstrated no relationship between adipose tissue thickness and EMD (r  =  −0.010, p  =  0.956). Collectively, these findings demonstrated that adiposity does not influence the estimation of EMD. (paper)