The Effect of Stretching on Nerve Excitability

Nerves are frequently stretched during movement. We investigate here the effect of stretch on nerve excitability within the framework of the soliton theory. This thermodynamic theory for nerve pulse propagation relies on the presence of a melting transition in the nerve membrane. In this transition, the area of the nerve membrane and the nerve thickness change. It depends on thermodynamic variables including temperature, the chemical potentials of anesthetics and on hydrostatic pressure. A further variable relevant for movement science is the the stretching of nerves, i.e., a tension in the nerve caused by muscle contraction, the bending of joints and the pulling on extremities. We show here that the soliton theory predicts a decrease in nerve excitability upon stretching. This becomes evident in a reduction of the amplitude of compound action potentials and in the suppression of reflexes. We compare these predictions with medical findings.