Grip Force Control in 21-Day Dry Immersion

Abstract

During space flight, the changes in the functions of the upper limbs can affect the quality of operator activity. At the same time, there are very few data on this topic, because most of the research is focused on the structure and functions of the lower extremities. The aim was to study the characteristics of the grip force control during the decrease of the support and proprioceptive sensory signals in the conditions of the ground-based model of the effects of space flight – dry immersion (DI). The duration of DI exposure was 21 days. 10 male volunteers performed tests using a hand dynamometer for maximal voluntary contraction, the maintenance of the reference force, the reproduction of this force from memory, and the grip force gradation test. The subjects performed this series of tests before exposure to DI, then on days 1, 3, 5, 10, 15, and 20 of DI, and days 1 and 3 of the recovery period. The results show that DI exposure led to an increase in proprioceptive sensitivity in the tasks without visual feedback when with open eyes from day 5 of DI the subjects were more mistaken in the reproduction of the reference force using the dominant hand. The sensory processing/modulation disorder under DI factors may cause this phenomenon.