The effect of quadriceps-electrocutaneous stimulation on the T-reflex and the H-reflex of the soleus muscle

Objective: To investigate the effect of ipsilateral quadriceps-electrocutaneous stimulation on the T-reflex and the H-reflex of the soleus muscle, and to examine the interactions in human cutaneous sensation – the soleus motoneuron pathway. Methods: The T-reflex and H-reflex tests were performed bilaterally on 50 able-bodied adults with a standardized technique using the soleus muscle. The reflexes were conditioned by electrocutaneous stimuli applied to the ipsilateral quadriceps using the optimal transcutaneous electrical nerve stimulation (TENS) machine (3×perception, intensity 15–30 mA). The conditioning stimuli were followed by reflex tests by 30–50 ms (conditioning A) and 80–100 ms (conditioning B). The latency and amplitude of the T-reflex and H-reflex were measured before (control) and after conditioning stimuli (A and B) and at sham (placebo). Results: There were no significant differences between the right and left sides and between the control and placebo in both T-reflex and H-reflex. There were significant differences in both latency and amplitude of the T-reflex only between control and conditioning A. There were no significant differences between control and conditioning tests in the H-reflex. Conclusions: The above results suggest that supraspinal center and cutaneous fusimotor reflexes, which increase the sensitivity of the soleus muscle spindle, mediate the observed motoneuron excitability changes.