Electromechanical delay (EMD) in symmetrical activity of the muscles stabilizing spinal column under static conditions

Electromechanical delay (EMD) is defined as the time between electrical excitation of a muscle and the onset of force generation. Duration of this delay for skeletal muscles ranges from 30 to 100ms. EMD has been reported to have effect on a number of mechanisms (Cavanagh and Komi 1979). Some studies report differences in EMD due to gender (Winter and Brookes 1991), age (Grosset et al. 2005), muscle fatigue (Zhou et al. 1996) and immobilization level (Kubo et al. 2000). Others authors have analysed its use for isometric (Kubo et al. 2001) or sprint training (Zhou et al. 1996). However, there are no reports which would relate this phenomenon to the analysis of symmetry in muscle activity. Therefore the authors focused on the investigations aimed at assessment and analysis of bioelectrical activity in the muscles which stabilize spinal column under static conditions. The assessment was made based on the analysis of EMG signal with particular consideration of the duration of electromechanical delay.