Postactivation Effect in the Deltoid Muscle of Healthy Young Subjects after a Short-Term “Dry” Immersion

Abstract: The objective of this study was to characterize, using surface electromyography (EMG), the postactivation effect (PAE) arising in the deltoid muscles of healthy young subjects after a single 45-min procedure of “dry” immersion (DI) used as a model of microgravity. The working hypothesis was that PAE had to decrease as a consequence of exposure to DI. But it has been established against the initial hypothesis that the PAE in deltoid muscles increased nearly twofold, from 66 to 135 s, without any statistically significant effects on the EMG amplitude or mean frequency. The following factors were considered in the study as probable contributors to the results: (1) the factor associated with the biomechanical function of deltoid muscles and the related probability of a “sensory conflict” between the DI effect and the necessity to maintain the balance function, (2) the factor of DI application conditions, (3) the factor of complexity in the task (a vertical posture) for the induction of PAE, and (4) the factor related to the involvement of the internal body representation system in the PAE manifestation. The obtained data are intended for the use in further studies on the effect of microgravity analogs on the muscle tone and rigidity in patients with Parkinson’s disease and its rehabilitation potential. © 2021, Pleiades Publishing, Inc.