Efferent responses to twitch tests used in identifying human muscle afferents.
The response of a muscle afferent to the mechanical stimulus produced by a twitch contraction of the receptor-bearing muscle is an important test for differentiating between muscle spindle endings and Golgi tendon organs. The present study demonstrates that active alpha-motor axons can behave in a similar manner to spindle afferents, presumably responding not to the mechanical event per se, but reflexly to the change in afferent discharge created by the mechanical event. alpha-Motor axons were unequivocally identified during microneurography using spike-triggered averages of EMG. Caution is required when the twitch test is utilized to assist in the classification of muscle afferents during an intentional or unintentional voluntary contraction.
Inglis
J T
JT
Faculty of Applied Health Science, Department of Physical Therapy, Elborn College, University of Western Ontario, London, Canada.
Wilson
L R
LR
Gandevia
S C
SC
Burke
D
D
D000200:Action Potentials; D004525:Efferent Pathways / Q000502:physiology; D004576:Electromyography; D006801:Humans; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction; D009470:Muscle Spindles / Q000502:physiology; D009132:Muscles / Q000294:innervation*; D009475:Neurons, Afferent / Q000502:physiology*