Electromechanical delay in a wrist flexor at various force levels for a power-grip tracking task

The purposes of this study were to determine: 1) the electromechanical delay (EMD) of the wrist musculature, and 2) if level of force output affects the EMD. These muscles are involved in various tool grasp/hand manipulation tasks that require widely varying levels of effort. The literature does not include EMD studies of the wrist musculature during gripping tasks. Therefore, it is useful to know if, and how, different levels of grip force affect the EMD. The values of EMDs in the literature span a range from approximately 40 to 140 ms, and differences in reported EMD durations of up to 300% exist for the same muscle under identical conditions. Proposed factors responsible for the EMD include: time for action potential propagation, release of calcium from sarcoplasmic reticulum, cross-bridge formation, and stretching of the muscle series elastic component (Norman and Komi, 1979).