Recruitment of Gastrocnemius Lateralis during walking in Parkinson's Disease assessed by EMG analysis

Quantitative assessment of muscle activity is generally evaluated by means of surface electromyography (sEMG), which records the changes in fibers action potential following a stimulation by α-motoneurons. sEMG alterations in people with Parkinson's disease (PD) have been widely documented in literature, as sEMG directly relates to the nervous system via the α-motoneurons. Recently, a novel algorithm has proposed Continuous Wavelet Transform (CWT) as a valuable tool to assess in time-frequency domain the mean regions of muscle activation during walking. Thus, the objective of the present work is to achieve a reliable assessment of Gastrocnemius Lateralis-muscle behavior during PD walking, by adopting CWT to interpret sEMG signals. Onset and offset timing of activity and the occurrence frequency, a recently introduced parameter useful for characterizing muscle-recruitment variability, were computed. Results reported a statistically significant (p<0.05) delay of Gastrocnemius Lateralis activity in PD in the early-stance phase, while an anticipatory strategy was revealed at the late-swing phase, yet not significant. The occurrence frequency parameter displayed an inhomogeneous distribution of the activation occurrence in PD patients during gait cycle; the authors might speculate that this underling information could suggest that people with PD prefer adopting a simpler motor control. Besides the information achieved in time domain, availability of frequency content of sEMG signal could be a further advantage, since it might be adopted to detect modifications in the electrophysiological behavior in people with PD. Thus, further studies could be focused on the attempt to quantify this parameter during walking in PD.