Related Experiment Videos
Accuracy of aimed arm movements in changed gravity
O Bock1, I P Howard, K E Money
1Institute for Space and Terrestrial Science, York University, North York, Ont., Canada.
Aviation, Space, and Environmental Medicine
|November 1, 1992
Summary
Arm movement accuracy decreases in altered gravity conditions, including hypergravity and microgravity. Adaptation requires prolonged exposure, suggesting proprioception and motor programs are key factors.
Area of Science:
- Human motor control
- Spaceflight physiology
- Sensorimotor adaptation
Background:
- Accurate aimed arm movements are crucial for daily tasks.
- Altered gravity environments, such as those experienced during spaceflight, pose challenges to sensorimotor control.
- Understanding how gravity affects motor control is vital for astronaut training and mission success.
Purpose of the Study:
- To investigate the accuracy of aimed arm movements under normal gravity, hypergravity, and microgravity conditions.
- To determine the role of visual cues and proprioception in motor control during altered gravity.
- To assess the time course of motor adaptation to changing gravitational forces.
Main Methods:
- Subjects performed visually-guided, arm-pointing movements towards targets in a mirror-view setup.
- Experiments were conducted during KC-135 parabolic flights, allowing for normal gravity, hypergravity (hyper-G), and microgravity (micro-G) phases.
- Pointing endpoint accuracy was quantified using a digitizing pad to record movement trajectories and final positions.
Main Results:
- Aiming accuracy was significantly impaired in hypergravity and microgravity compared to normal gravity, with pointing errors increasing in altered gravitational states.
- The observed pointing errors persisted even when targets were viewed only in normal gravity, indicating a reduced influence of the 'elevator illusion'.
- Pointing accuracy showed improvement within a single movement but not across successive parabolic flight repetitions, suggesting limited rapid adaptation.
Conclusions:
- Altered gravity conditions, specifically hypergravity and microgravity, degrade the accuracy of aimed arm movements.
- Proprioceptive feedback degradation and/or maladapted motor programs are likely contributors to the observed motor control impairments.
- Sustained adaptation to altered gravity for arm movements requires prolonged exposure beyond the duration of individual parabolic flight episodes.