Reduced gravity weakens muscle activation coupling and destabilizes bimanual force control.

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Gravity significantly influences coordinated bimanual motor control.
• Neural mechanisms underlying force control in reduced gravity are not well understood.

Purpose of the Study:

• To investigate frequency-specific neural mechanisms of bimanual isometric force coordination across varying gravity levels.
• To examine how altered gravity affects motor performance and neural activity.

Main Methods:

• Twelve adults performed bimanual isometric force tasks at 0, 0.25, 0.50, 0.75, and 1 g during parabolic flight.
• Electromyography (EMG) of bilateral triceps was recorded, and intermuscular coherence was analyzed in alpha, beta, low-gamma, and high-gamma bands.
• Force output variability and phase coordination were assessed.

Main Results:

• Reduced gravity decreased mean force output and increased force variability.
• Intermuscular coherence in the 5-60 Hz range decreased with lower gravity.
• Phase-locking strength was maintained, but phase error increased in challenging tasks at 0 g.
• Reduced beta-band coherence correlated with improved force steadiness at 0 g.

Conclusions:

• Gravity modulates neural mechanisms of motor stability and coordination.
• Beta and low-gamma band neural synchrony are critical for skilled coordination in altered gravity.
• Findings suggest potential targets for countermeasures to support motor control in spaceflight or other reduced-gravity environments.