EMG signals recorded during elicited reflexes. Single differential (SD) and double differential (DD) surface electromyography (sEMG) and intramuscular electromyography (iEMG) signals recorded during a genuine reflex response involving activity in either the tibialis anterior (TA) or the soleus (SOL) muscle exclusively. When evaluating SD sEMG only, both visual inspection following the fixed criteria proposed in  and automated evaluation of a standardized scoring criterion (interval peak z-score) indicate reflex responses involving both muscles. However, the DD sEMG and iEMG signals reveal that genuine muscle activity is present in only one of the two muscles depending on the stimulation site.
Jensen et al. BMC Neuroscience 2013 14:39 doi:10.1186/1471-2202-14-39