Identification of Changing Lower Limb Neuromuscular Activation in Parkinson’s Disease during Treadmill Gait with and without Levodopa Using a Nonlinear Analysis Index

Figure 4

Neuromuscular activity of tibialis anterior (TA) muscle during a gait cycle depicted by EMG activity. (a) TA is active during the initial phase of gait cycle (heel contact), with a reduction of activity towards the plantar flexion position. From the midstance toward the terminal stance, the dorsiflexion of ankle is managed by higher activity of TA. The recurrence plots (RP) generated based on the original data are shown in graph (b) indicating the existence of a specific pattern in TA activity during the gait cycle. This pattern is depicted by several recurrent points located along particular diagonal lines which are parallel to the main diagonal line. The outcome of the RQA also verified the existence of the aforementioned pattern (%REC = 1.93, %DET = 34.80, radius = 1.92 (maximum scale), and ApEn = 0.63). (c) contains the randomized shuffled data of the signal shown in (a); (d) is the RP of the randomized signal which shows no significant determinism in the shuffled data. The time delayed dimensional data in RP are randomly scattered around the main diagonal line and the recurrent points are positioned along very short length. In addition, the outcome of RQA has shown significant reduction in determinism in the randomized data (%REC = 0.44, %DET ≅ 0, radius = 1.92 (maximum scale), and ApEn = 1.93). The significant drop in the determinism of the signal detected by decreasing %DET and increasing ApEn verified the nonlinear dynamics of the collected EMG signal.

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