Neurophysiological effects of partial gravity on bimanual control: a parabolic flight study

Bimanual coordination is essential for many spaceflight tasks, yet the effects of altered gravity on its behavioral and neural underpinnings remain unclear. This study examined the influence of microgravity (0 g) and partial gravity (0.25-0.75 g) on isometric bimanual coordination during parabolic flight. Participants performed rhythmic force tasks while force and electromyography (EMG) data were collected. Results indicated that mean force and force smoothness differed across gravity conditions, with the most pronounced behavioral impairments occurring in microgravity. Performance under partial gravity (0.25-0.75 g) generally trended toward the 1 g condition. At the neural level, exploratory EMG-EMG cross-wavelet analysis indicated reduced beta band (13-30 Hz) interlimb coordination in 0 g compared with 1 g, whereas traditional coherence measures did not show differences related to gravity. These neural findings should be interpreted cautiously and as exploratory rather than confirmatory. The findings suggest that the absence of gravitational loading is associated with the greatest challenges for coordinated motor output, while partial loading may help preserve performance. These results have implications for astronaut training and countermeasure development for future lunar and Martian missions.