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A spinal pathway between synergists can modulate activity in human elbow flexor muscles
Benjamin K Barry1, Zachary A Riley, Michael A Pascoe
1Department of Integrative Physiology, University of Colorado, Boulder, CO 80309, USA. ben.barry@unsw.edu.au
Experimental Brain Research
|July 4, 2008
Summary
Electrical stimulation of the brachioradialis nerve inhibits biceps motor units. This reflex
Area of Science:
- Neuroscience
- Human Physiology
- Motor Control
Background:
- Electrical stimulation of the brachioradialis branch of the radial nerve can inhibit motor units in the biceps brachii during weak contractions.
- Understanding this inhibitory reflex is crucial for comprehending muscle synergies and motor control.
Purpose of the Study:
- To characterize the inhibitory reflex from the brachioradialis to the biceps brachii.
- To compare the reflex strength between the short and long heads of the biceps brachii.
- To investigate the influence of forearm position on the reflex strength.
Main Methods:
- Spike-triggered stimulation was employed to assess the effect of radial nerve stimulation on single motor unit discharge in the biceps brachii.
- Fifteen subjects participated in the study.
- Motor unit activity was recorded during varying forearm positions (pronation, neutral, supination).
Main Results:
- Radial nerve stimulation significantly prolonged the interspike interval of motor units in both the long and short heads of the biceps brachii.
- No significant difference in inhibition strength was found between the two biceps heads.
- The strength of the inhibitory reflex varied with forearm position, being greatest in pronation and least in supination.
Conclusions:
- The inhibitory reflex from the brachioradialis to biceps brachii motor units is modulated by forearm posture.
- This reflex pathway provides a spinal mechanism for adjusting biceps activation based on forearm position, contributing to muscle synergy.
- The findings highlight a neural basis for coordinating arm movements in humans.
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