 We will use two different reflex protocols to test the long descending propriospinal system. The long propriospinal system will be tested based on H reflex amplitude in the Soleus muscle under conditioning stimulation of ulnaris nerve. The ulnaris nerve will be stimulated via surface electrodes with trains of 3 rectangular pulses pulse duration: 0.5 ms, pulse interval: 3 ms. In normal subjects the amplitude of H reflex in the Soleus muscle increases when the delay between conditioning and testing stimuli is 40 ms. 