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Rhesus leg muscle EMG activity during a foot pedal pressing task on Bion 11
J A Hodgson1, S N Riazansky, C Goulet
1Department of Physiological Science, University of California, Los Angeles, USA.
Journal of Gravitational Physiology : a Journal of the International Society for Gravitational Physiology
|September 7, 2001
Summary
Spaceflight significantly reduced lower limb muscle activity in rhesus monkeys, with soleus and medial gastrocnemius showing immediate and substantial declines. Ground simulations did not fully replicate these microgravity-induced changes.
Area of Science:
- Neuroscience
- Space Physiology
- Biomechanics
Background:
- Understanding the physiological effects of microgravity is crucial for astronaut health.
- Previous research indicates muscle atrophy and functional changes occur during spaceflight.
- The specific impact of microgravity on lower limb muscle activity during a task is not fully elucidated.
Purpose of the Study:
- To investigate the effects of spaceflight and simulated microgravity on lower limb muscle activity in rhesus monkeys performing a motor task.
- To compare the immediate effects of actual spaceflight with a ground-based simulation.
Main Methods:
- Rhesus monkeys were trained on a foot lever pressing task for food reward.
- Electromyography (EMG) activity was recorded from lower limb muscles before, during, and after spaceflight and ground simulation.
- Integrated EMG activity was quantified during a 20-minute test session.
Main Results:
- Spaceflight led to a significant reduction in soleus (Sol) muscle activity to 25% of preflight levels.
- Medial gastrocnemius (MG) activity was also reduced to 25% of preflight levels during spaceflight.
- Ground simulation resulted in a 50% reduction in Sol activity but showed normal MG activity, indicating differences from actual microgravity.
Conclusions:
- Microgravity causes immediate and substantial reductions in soleus and medial gastrocnemius muscle activity during a motor task.
- Ground-based simulations do not fully replicate the neuromuscular effects of spaceflight on these lower limb muscles.
- These findings highlight the profound impact of microgravity on motor control and muscle function.