The Diversity of Adaptative Responses Following G-Transitions During Spaceflight

Spaceflight drives adaptive changes appropriate for sensorimotor function in an altered gravity environment. Adaptive changes in microgravity can be maladaptive for return to earth's gravity. The inter-individual variability of sensorimotor decrements has been striking. This has been characterized primarily through motion sickness reports, neurological exams, computerized dynamic posturography, and functional field tasks (sit-to-stand, prone-to-stand and tandem walk). Reduced motion sickness prevalence in repeat fliers and anecdotal reports of retention of fine motor strategies needed to control motion suggest that prior flight experience benefits readaptation to the novel “microgravity” state. The effects of prior flight experience for readaptation to the familiar terrestrial environment are less clear. Comparison of terrestrial readaptation from the Shuttle and longer duration International Space Station (ISS) missions demonstrates considerable overlap in the initial decrements with longer duration flights requiring a longer time course of recovery. In addition to the large intersubject variability within specific measures, differences exist across outcome measures such that performance on one test may not correlate with performance on another test. While some “preflight” biomarkers have shown association with specific post-landing outcomes, the absence of a comprehensive spaceflight analog makes prediction of outcomes measures challenging. Outcome measures from prior flights appear to be the best predictors of similar outcomes on future flights. An overview will be provided of the upcoming Artemis missions that will return crews to the lunar surface. Early sensorimotor decrements following g-transitions have implications for the completion of critical mission tasks in-mission and returning crewmembers to activities of daily living following these exploration missions. Both assessments to characterize the risks and interventions to optimize crew performance will be necessary for success on these missions.