Muscle spindle feedback differs between the soleus and gastrocnemius in humans.
The Hoffmann (H) reflex and motor (M) response were studied in soleus and gastrocnemius during voluntary contraction in eight male volunteers.


OBJECTIVE
To determine if the strength of spindle input to the muscles is the same. To assess if the M response size changes during contraction.


RESULTS
The size of the maximum M response (M max) changed during contraction in each subject. Hence, all H reflex measurements were normalized to the M max at each level of contraction for each subject. The largest H/M max was bigger in soleus than gastrocnemius at every contraction level. The overall largest H/M max for soleus (97%) and gastrocnemius (55%) were achieved at 40 and 100% maximum voluntary contraction (MVC), respectively.


CONCLUSIONS
Soleus receives greater spindle feedback than the gastrocnemius both at rest and during voluntary contraction.
Tucker
K J
KJ
Discipline of Physiology, School of Molecular and Biomedical Sciences, University of Adelaide, SA 5005, Australia.
Türker
K S
KS
D000293:Adolescent; D000328:Adult; D025461:Feedback, Physiological / Q000502:physiology; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009470:Muscle Spindles / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*