Abstract des Autors

The dependence of the conduction velocity of the action potential on the spike interval from a preceding potential was studied using human single motor units during voluntary muscle contraction. The spike potential was recorded from the surface of the skin overlying M. vastus medialis by use of surface electrodes. The results were as follows: 1) Conduction velocity increased with a decrease in spike interval. The relation between conduction velocity and spike interval can be expressed as log v = kt + a, where v is conduction velocity (m/s), t is spike interval (Ms) and k and a are constants. All data can be expressed by the above formula with a highly significant correlation. 2) After arterial occlusion, there was little or no relation between conduction velocity and spike interval. 3) Effects similar to occlusion could be seen in the result of prolonged isometric contraction. 4) At low muscular temperature, the relation could not be described by a logarithmic regression. The mechanisms of these changes are still uncertain but some possible factors can be considered, for example, composition of the extracellular fluid, pH, temperature and permeability of the excitable membranes of the muscle. (gekuerzt)