H-reflex changes during contractions of the ankle extensors in spastic patients.
Soleus H-reflexes during tonic contractions and isometric ramp contractions of the ankle extensors in spastic and healthy subjects were measured. During the tonic contractions, the H-reflex increased with the contraction level. The increase was highest in the patients (p < 0.001). The facilitation of the H-reflex during a ramp contraction is due to a static component resulting from the increased excitation level and a dynamic component resulting from the modulation of the H-reflex. The dynamic H-reflex facilitation during the ramp contraction was decreased in the patients (p < 0.05). The findings suggest that there is a decreased H-reflex control in spastic patients and this could be explained by a decreased presynaptic inhibition or by postsynaptic changes.
Toft
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E
Department of Medical Informatics and Image Analysis, Aalborg University, Denmark.
Sinkjaer
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T
D000328:Adult; D000843:Ankle Joint / Q000294:innervation; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology; D009103:Multiple Sclerosis / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology*; D009128:Muscle Spasticity / Q000503:physiopathology*; D009129:Muscle Tonus / Q000502:physiology; D009132:Muscles / Q000294:innervation; D011999:Recruitment, Neurophysiological / Q000502:physiology; D012026:Reflex, Stretch / Q000502:physiology; D013979:Tibial Nerve / Q000503:physiopathology