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Post-contraction changes in human muscle spindle resting discharge and stretch sensitivity
E Ribot-Ciscar1, M F Tardy-Gervet, J P Vedel
1Laboratoire de Neurobiologie Humaine, Université Aix-Marseille I, URA CNRS 372, France.
Experimental Brain Research
|January 1, 1991
Summary
Voluntary muscle contraction in humans did not show a post-contraction sensory discharge. However, it altered muscle spindle sensitivity, potentially aiding the nervous system in processing future stretch movements.
Area of Science:
- Neuroscience
- Human Physiology
- Motor Control
Background:
- Muscle spindles are sensory receptors crucial for proprioception.
- Understanding their response to voluntary contraction is key to motor control research.
- Previous animal studies suggested a post-contraction sensory discharge.
Purpose of the Study:
- To investigate after-effects of voluntary isometric contraction on human muscle spindle primary endings.
- To assess changes in resting discharge and response to stretch after contraction.
Main Methods:
- Microneurography was used to record activity from muscle spindle primary endings in the lateral peroneal nerve.
- Subjects performed voluntary isometric contractions.
- Responses to slow ramp stretches were analyzed before and after contraction, with adjustments for silent periods.
Main Results:
- Most human muscle spindle primary endings did not exhibit a post-contraction sensory discharge.
- Isometric voluntary contraction reduced the stretch threshold and dynamic sensitivity of muscle spindles.
- These changes suggest modulation by static fusimotor neurons.
Conclusions:
- Human muscle spindles do not show the same post-contraction discharge as observed in animals.
- Contraction-induced changes in muscle spindle sensitivity may enhance the coding of upcoming stretch information.
- Coactivation of alpha and gamma motoneurons during contraction facilitates the processing of proprioceptive feedback for movement control.