[Effect of immersion hypokinesia on the parameters of human muscle potentials]

During 3-day immersion hypokinesia stimulation muscle potentials and averaged potentials of total EMG of m. biceps brachii were investigated in six test subjects. Stimulation potentials were obtained by exciting n. cutaneous with a train of square impulses. Potentials were recorded using a combined multi + electrode. Averaged potentials of total EMG were recorded by means of the same electrode. The propagation rate of the potentials, duration of their negative and end-positive phases as well as the length of their negative phase in space were measured. In addition, vector-electromyographic images of the potentials were recorded. After immersion hypokinesia the propagation rate decreased significantly, the duration of the end-positive phase increased and the length of the depolarized zone of potentials in space shortened. The decrease of the rate of propagation of stimulation potentials was 28% and that of averaged potentials of total EMG was 31% per group. These changes developed rapidly enough, indicating shifts in the properties of potentials of action of myofibers during immersion. Factors responsible for these changes are discussed.