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Sympathetic nerve activity does not reduce proprioceptive acuity in humans.
1Department of Physiology, National Institute of Occupational Health, Oslo, Norway.
Acta Physiologica Scandinavica
|June 26, 2003
Summary
Increased muscle sympathetic activity, induced by cold pressor tests or glucose, did not impair ankle proprioception in humans. Contrary to animal studies, findings suggest sympathetic activation may enhance proprioceptive acuity.
Area of Science:
- Neuroscience
- Human Physiology
- Motor Control
Background:
- Proprioception is crucial for movement coordination and muscle control.
- Animal studies suggest sympathetic nerve stimulation reduces muscle spindle sensitivity.
- Stress-induced proprioception changes may impair fine motor control.
Purpose of the Study:
- To investigate if increased muscle sympathetic activation alters human proprioception.
- To examine the effect of sympathetic nervous system activity on movement detection thresholds.
Main Methods:
- Eight healthy subjects underwent movement detection threshold tests for the right ankle.
- Muscle sympathetic activity was increased using a cold pressor test (CPT) and oral glucose ingestion (GLUC).
- Plasma noradrenaline (NA) and mean arterial pressure (MAP) were measured.
Main Results:
- CPT significantly increased plasma NA and MAP, but movement thresholds remained unchanged.
- GLUC also significantly increased plasma NA and MAP.
- Following GLUC, the movement threshold for flexion decreased, suggesting enhanced muscle spindle sensitivity.
Conclusions:
- Findings contradict animal studies and the hypothesis that sympathetic activity reduces proprioceptive acuity.
- Increased muscle sympathetic activation, particularly after glucose intake, may enhance proprioceptive sensitivity in humans.
- Human proprioception appears resilient to sympathetic nervous system modulation.