Stressors affect human motor timing during spaceflight.

Crewed outer-space missions require adequate motor capacity among astronauts, whose sensorimotor system is disturbed by microgravity. Stressors other than microgravity, e.g., sleep loss, confinement, and high workload, characterize the living experience in space and potentially affect motor performance. However, the evidence of these stressors remains elusive. We recruited twelve taikonauts from the China Space Station to conduct a motor timing task that minimized the effect of microgravity on motor performance. Participants showed a remarkable increase in motor timing variance during spaceflight, compared to their pre- and post-flight performance and that of ground controls. Model-based analysis revealed that their timing deficits were driven by increased central noise instead of impaired motor execution. Our study provides evidence that nonspecific stressors can profoundly affect motor performance during spaceflight.