Methodological implications of the post activation depression of the soleus H-reflex in man |
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Authors: | C Crone J Nielsen |
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Institution: | (1) Department of Neurophysiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark;(2) Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark |
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Abstract: | Summary A long lasting inhibition (> 8 s) of the soleus Hoffmann reflex (H-reflex) was evoked by a preceding soleus H-reflex, by a brief voluntary ankle flexor or extensor muscle contraction or by a tap applied to the Achilles tendon. The time course of this long lasting inhibition was similar in all these cases, suggesting that the same spinal mechanism is involved. Furthermore, it was shown that the post-activation depression may interfere with the determination of inhibitory or facilitatory effects on the H-reflex. It is stressed that when the onset of inhibitory or facilitatory effects on the soleus H-reflex is to be determined in relation to start of an ankle movement, either very long stimulus intervals (> 8 s) must be used, or the onset must be determined in relation to a reference value of the soleus H-reflex, which may be influenced by the long lasting inhibitory effect, but not yet by the succeeding muscle contraction. |
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Keywords: | Hoffmann reflex Stimulus frequency Long lasting depression Reciprocal inhibition Man |
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