Functional Task and Balance Performance in Bed Rest Subjects and Astronauts.

INTRODUCTION: The purpose of this study was to determine how short- and long-duration spaceflight affects astronauts' performance on functional tests that challenge the balance control system (Seated Egress and Walk; Object Translation; Recovery from Fall/Stand; and Jump Down) and on clinical tests of balance function (Computerized Dynamic Posturography and Tandem Walk). In addition, we examined how exercise affects functional performance after long-term axial body unloading during 70 d of bed rest at 6° head-down tilt. METHODS: Data were collected twice during the 2-mo period before spaceflight or during the 2-wk period before bed rest, and four times after flight or bed rest: on the day of landing or the day bed rest ended, 1 d and 6 d later, and a final session 12 d after bed rest or 30 d after spaceflight. RESULTS: For bed rest subjects, long-term axial unloading alone caused functional performance deficits immediately after bed rest. However, the addition of an exercise regimen did not significantly improve median functional performance immediately after this axial unloading. For spaceflight subjects, the length of the space mission was directly related to the severity of functional performance deficits within 1 d of landing and during the subsequent recovery period after flight. DISCUSSION: The performance data suggest that an additional sensorimotor-based countermeasure may be necessary to maintain functional performance at preflight levels immediately after spaceflight.Miller CA, Kofman IS, Brady RR, May-Phillips TR, Batson CD, Lawrence EL, Taylor LC, Peters BT, Mulavara AP, Feiveson AH, Reschke MF, Bloomberg JJ. Functional task and balance performance in bed rest subjects and astronauts. Aerosp Med Hum Perform. 2018; 89(9):805-815.

Physiological and Functional Alterations after Spaceflight and Bed Rest.

INTRODUCTION: Exposure to microgravity causes alterations in multiple physiological systems, potentially impacting the ability of astronauts to perform critical mission tasks. The goal of this study was to determine the effects of spaceflight on functional task performance and to identify the key physiological factors contributing to their deficits. METHODS: A test battery comprised of seven functional tests and 15 physiological measures was used to investigate the sensorimotor, cardiovascular, and neuromuscular adaptations to spaceflight. Astronauts were tested before and after 6-month spaceflights. Subjects were also tested before and after 70 d of 6° head-down bed rest, a spaceflight analog, to examine the role of axial body unloading on the spaceflight results. These subjects included control and exercise groups to examine the effects of exercise during bed rest. RESULTS: Spaceflight subjects showed the greatest decrement in performance during functional tasks that required the greatest demand for dynamic control of postural equilibrium which was paralleled by similar decrements in sensorimotor tests that assessed postural and dynamic gait control. Other changes included reduced lower limb muscle performance and increased HR to maintain blood pressure. Exercise performed during bed rest prevented detrimental change in neuromuscular and cardiovascular function; however, both bed rest groups experienced functional and balance deficits similar to spaceflight subjects. CONCLUSION: Bed rest data indicate that body support unloading experienced during spaceflight contributes to postflight postural control dysfunction. Further, the bed rest results in the exercise group of subjects confirm that resistance and aerobic exercises performed during spaceflight can play an integral role in maintaining neuromuscular and cardiovascular functions, which can help in reducing decrements in functional performance. These results indicate that a countermeasure to mitigate postflight postural control dysfunction is required to maintain functional performance.