Cross-talk from other muscles can contaminate EMG signals in reflex studies of the human leg

The extent of contamination of the whole muscle surface electromyogram (SEMG) was studied using the classical H-reflex preparation of the human leg. SEMG and single motor unit activity were recorded from the soleus and the anterior tibial muscles in response to a low intensity stimulation of the tibial nerve at the popliteal fossa. The SEMGs of individual motor units were established to compare with the whole muscle SEMG in order to determine the presence of the cross-talk. It was shown that the whole muscle SEMG can be contaminated by the activity from the antagonists especially at high stimulation intensities.