Propagation velocity of muscle action potentials in the growing normal child.

Power spectrum analysis of myoelectric signals has been used to measure the propagation velocity in a large number of voluntary action potentials in biceps and brachioradialis muscles of normal children, 0-20 years old. The method used can be applied to both single motor units signals and interference electromyogram. From measurements of single motor units, the distribution of potential velocities in the muscle can be obtained, which makes conclusive statements on the development of the velocity during childhood more reliable. The propagation velocities are found to increase with age, body height, and muscle diameter. The dependencies on these size parameters are close to that of the square root function, in accordance with electrophysical theory.