Effect of muscle length on distribution of muscle fiber conduction velocity for M. biceps brachii.

The influence of the muscle length on the distribution of muscle fiber conduction velocity (MFCV) was estimated at 3 different elbow angles (90 degrees, 120 degrees and 150 degrees) during the contraction of 30% of isometric maximum voluntary contraction (MVC). Surface electromyogram was recorded in the distal region of m. biceps brachii using a surface array electrode. MFCVs at the different locations from the end-plate to the distal tendon of the muscle were measured directly using the averaging method. MFCVs near the end-plate and the distal tendon of the muscle showed the high values, while MFCVs in the middle region between the end-plate and the distal tendon of the muscle had low values at the same elbow angles. The mean MFCVs in the middle region decreased when the muscle length increased during the contraction of 30% MVC. The middle region length changed when the elbow joint was extended from the elbow angle of 90 degrees to that of 150 degrees. Although previous studies showed the influence of muscle length on MFCV for special regions (like end-plate, tendon, and middle region), MFCV for whole regions, that is, the distribution of MFCV has not been studied for various muscle length. The MFCV for the same region in the some muscle length could not be estimated. In the study, the distribution of MFCV in various muscle length for the contraction of 30% MVC was obtained, and the model with the function including muscle length for the estimation of MFCV was presented.