02050nas a2200181   4500008004100000022001400041245012100055210006900176260001200245300001400257490000800271520148300279653001101762653001201773100001501785700002101800856004701821       1988                        eng d  a0014-488600aJendrassik maneuver facilitates soleus H-reflex without change in average soleus motoneuron pool membrane potential.0 aJendrassik maneuver facilitates soleus Hreflex without change in  c08/1988  a288–3020 v1013 aFacilitation of spinal reflex amplitude by remote muscle contraction, otherwise known as the Jendrassik maneuver (JM), was first shown over 100 years ago, yet the mechanism by which this facilitation operates remains undetermined. Earlier work has eliminated participation of the muscle spindle in JM-induced spinal reflex facilitation, leaving changes in postsynaptic (e.g., change in average soleus motoneuron membrane potential) and presynaptic (e.g., inhibition of presynaptic inhibition) mechanisms as viable candidates. We recorded background EMG in the soleus muscle during JM-induced soleus H-reflex facilitation in humans. The JM in this experiment consisted of wrist muscle contraction. Soleus background EMG was maintained by the subject at either a zero level (e.g., relaxed) or a specified moderate level prior to and during the JM. The JM increased H-reflex amplitude by comparable amounts in both situations, but had no effect on soleus background EMG. Given the well-known relationship between the average motoneuron pool membrane potential and background EMG, we conclude that JM facilitation of the soleus H-reflex is not caused by an increase in background excitatory input to the soleus motoneuron pool. Remaining candidates for mediation of JM induced H-reflex facilitation include change in stimulus-evoked afferent input at some point proximal to the muscle spindle, such as reduction in presynaptic inhibition, or a change in motoneuron input resistance.10aReflex10aStretch1 aDowman, R.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/3396646