Kinematic synergy adaptation to microgravity during forward trunk movement

Area of Science:

• Human physiology
• Biomechanics
• Neuroscience

Background:

• Equilibrium control relies on kinematic synergies for upper trunk movement.
• Understanding how these synergies adapt to altered gravity is crucial for space travel and rehabilitation.

Purpose of the Study:

• To investigate if the kinematic synergy for equilibrium control during upper trunk movement is maintained without gravity constraints.
• To compare trunk movement dynamics and muscle activity in normal gravity versus microgravity.

Main Methods:

• Subjects performed forward trunk movements in both normal gravity and during parabolic flight microgravity.
• Kinematic synergy was analyzed using principal component analysis of joint angle changes.
• Electromyographic (EMG) patterns of key muscles were recorded.

Main Results:

• The anteroposterior center of mass (CM) position was minimized in microgravity, despite the absence of equilibrium constraints.
• The joint coupling characteristic of the kinematic synergy was preserved in microgravity, indicating CNS control.
• EMG patterns underlying the synergy were significantly reorganized in microgravity.

Conclusions:

• The kinematic synergy for minimizing anteroposterior CM shift is preserved in short-term microgravity.
• This preservation is achieved through rapid adaptation of muscle forces to the new gravitational environment.
• The central nervous system (CNS) demonstrates remarkable adaptability in maintaining movement synergies.