Mission-critical tasks for assessing risks from vestibular and sensorimotor adaptation during space exploration

Abstract

To properly assess the risk induced by vestibular and sensorimotor adaptation during exploration missions, we examined how long-duration stays on the International Space Station affect functional performance after gravity transitions. Mission-critical tasks that challenge the balance and the locomotion control systems were assessed: i.e., sit-to-stand, recovery-from-fall, tandem-walk, and walk-and-turn. We assessed 19 astronauts, including 7 first-time flyers and 12 experienced flyers, before their flight, a few hours after landing, and then 1 day and 6-11 days later. Results show that adaptation to long-term weightlessness causes deficits in functional performance immediately after landing that can last for up to 1 week. No differences were observed between first-time and experienced astronaut groups. These data suggest that additional sensorimotor-based countermeasures may be necessary to maintain functional performance at preflight levels when landing on planetary surfaces after a long period in weightlessness.

Keywords: adaptation; functional performance; sensorimotor system; spaceflight; vestibular tests.

FIGURE 1

Performance decrements associated with sensorimotor disturbances occur during and after gravity (G) transitions. Photos credit NASA.

FIGURE 2

Schematic illustrating the calculation of the start and end of the sit-to-stand task based on the trunk pitch velocity.

FIGURE 3

Balance tasks. Time required to assume a stable standing posture from a seated position (A) and a prone position (B) for 19 astronauts before (Pre) and after spaceflight. Each symbol represents the data from an individual subject and the horizontal blue lines represent the subjects mean for each major time point. The dotted line represents the mean of all preflight measures. *p < 0.05 relative to preflight values.

FIGURE 4

Locomotion tasks. Percent of correct steps during the tandem-walk test with eyes open (A) and with eyes closed (B) for 19 astronauts before (Pre) and after spaceflight. Time to complete the obstacle course (C) and turn rate around the cone (D) during the walk-and-turn task for 7 astronauts before (Pre) and after spaceflight. Each symbol represents the data from an individual subject and the horizontal blue lines represent the subjects mean for each major time point. The dotted line represents the mean of all preflight measures. *p < 0.05 relative to preflight values.