Asymmetry of electromechanical delay (EMD) and torque in the muscles stabilizing spinal column.

Stabilization of the spinal column is ensured by the activity of trunk flexor and erector muscles, including rectus abdominis (RA) and erector spinae (ES). The goal of this study was to evaluate the symmetry of action potential and electromechanical delay (EMD) in RA and ES during generation of maximal muscle torque. In the present study, the symmetry of EMG activity in the right and left parts of RA and ES was tested under isometric conditions. The subjects (N = 13) were selected from the university population. Electromyographic signals and muscles torques were recorded with the sampling frequency of 1000 Hz. Lack of significant differences in EMD between left and right sides in both muscles studied and lack of correlation between EMD and maximal muscle torque were observed. Analysis aimed at assessing the symmetry of EMG signals amplitude revealed crossed laterality characterized by increased activity in the right side of RA muscle and left side of ES. The proportion of maximal muscle torque in ES to RA in the women examined amounted to 1.7:1.