Relation between electromyogram and torque of isometric reflex contractions in man.
Human subjects maintained isometric plantar or dorsal flexions of the ankle in a matching task. H-reflexes of different sizes were superimposed on the steady activity. The peak-to-peak amplitude of the reflexes was measured on the electromyogram (EMG) of the soleus muscle. The size of the corresponding muscle contractions was determined on the isometric torque signal in relation to the maintained flexion force. The EMG-torque relation which was defined as the reflex muscle contraction as a function of the EMG reflex signal approximated a square root function for a given steady contraction level. It was not modulated by steady dorsal flexions, but it decreased continuously with stronger plantar steady torques. This dependence was caused by the silent period following the reflex discharge. Since the reflex discharge and the silent period were near in time to the duration of the contraction, the silent period had a direct effect on the reflex contraction amplitude.
Institute of Physiology, University of Fribourg, Switzerland.
D G
DG
Ruegg
M
M
Fluri
D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D009119:Muscle Contraction; D012018:Reflex