Gravity as a contextual control parameter in coordination dynamics: Phase-specific stability during parabolic flight

Area of Science:

• Motor Control and Coordination Dynamics
• Human Physiology in Altered Gravity

Background:

• Coordination dynamics explains how movement patterns emerge from interacting constraints.
• The Haken-Kelso-Bunz (HKB) model predicts stability of in-phase (0°), anti-phase (180°), and 90° coordination modes.
• The influence of gravity on these dynamics is largely unexplored, despite known roles of visual and tactile feedback.

Purpose of the Study:

• To investigate gravity's role as a contextual control parameter in human coordination dynamics.
• To determine how varying gravitational forces reshape the stability of bimanual coordination patterns.
• To assess the impact of microgravity, partial gravity, and Earth gravity on motor performance.

Main Methods:

• Participants performed bimanual isometric force tasks with Lissajous feedback at 0°, 90°, and 180° relative phase.
• Experiments were conducted during parabolic flight, simulating microgravity (0 g) and partial gravities (0.25-0.75 g), alongside 1 g (Earth gravity).
• Evaluated coordination accuracy, bias, stability, and unimanual timing and force control.

Main Results:

• At 1 g, performance aligned with HKB predictions (0° most stable, 90° least).
• Microgravity destabilized coordination, causing increased variability and drifts towards the 0° pattern.
• Partial gravity partially restored stability for 90° and 180° tasks, with higher g-levels improving performance.

Conclusions:

• Gravity acts as a graded, task-dependent control parameter influencing the coordination landscape.
• Altered gravity environments significantly reshape motor control dynamics.
• Findings have implications for motor performance and training strategies in space and other altered-gravity settings.