Jump Tests after Support Unloading of Various Durations: Maximum Height and Accuracy of Implementation

The paper presents results of a study of changes in speed-strength factors of the musculoskeletal system of the human lower extremities and factors of accuracy in performing multi-joint movements after exposure to such models of the physiological effects of microgravity as 21-day head-down bed rest (HDBR) and 7-day dry immersion (DI) with electromyostimulation (EMS) as a preventive measure against muscle atony. Maximum jump height, as well as the accuracy and variability of the jump height to a predetermined height were studied. The results of the study showed that exposure to the microgravity models has a similar effect on the absolute speed-strength parameters of lower extremities muscles and leads to their decrease. At the same time, HDBR and DI have different effects on the accuracy of performing multi-joint movements to a predetermined height. Thus, after HDBR, the accuracy increased, and after DI it decreased or remained at the background level. The mentioned decrease in the accuracy after DI may be a consequence of the use of EMS during DI.