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Positive afferent feedback to the human soleus muscle during quiet standing
Author(s) -
Van Doornik Johan,
Azevedo Coste Christine,
Ushiba Junichi,
Sinkjær Thomas
Publication year - 2011
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21952
Subject(s) - soleus muscle , electromyography , ankle , isometric exercise , afferent , achilles tendon , anatomy , medicine , physical medicine and rehabilitation , chemistry , tendon , skeletal muscle
In this study we investigated the mechanisms responsible for soleus muscle contraction during quiet standing. Methods: Subjects stood on a platform that was randomly moved forward or downward or rotated around the ankle. Results: Downward perturbation caused a short‐latency drop in averaged rectified soleus electromyography (SOL EMG). SOL drop increased monotonically with downward acceleration amplitude. Ischemia above the knee abolished or diminished this drop. Ischemia above the ankle had no diminishing effect. Vibration of the Achilles tendon had a diminishing effect on the amplitude of SOL responses. Conclusions: The short‐latency drop in SOL observed for downward perturbation might be due to a decrease in positive afferent feedback due to the sudden decrease in body weight. This implies the existence of an ongoing afferent feedback loop toward the SOL motoneuron pool from force‐sensitive receptors. Both Ia and Ib afferents probably play a role in the responses observed. Muscle Nerve, 2011