Characteristics of the electromyographic patterns of lower limb muscles during gait in patients with Parkinson's disease when OFF and ON L-Dopa treatment

The purpose of this study was to compare the electromyographic (EMG) behavior of the triceps surae (TS), tibialis anterior (TA), quadriceps and hamstring muscles of the lower limbs during self-initiated free gait in a group of patients (n=15) with Parkinson's disease (PD), when OFF and ON L-Dopa, with that of normal controls. When OFF L-Dopa, we observed qualitative disturbances in muscle activation patterns, such as an absence or extreme reduction in TA activations in early stance or during the early and late swing phases. Other disturbances included flatter profiles of the TS activation burst at push off, and temporal alterations that included prolonged activation of the proximal muscles during the stance phase. Statistical analysis showed that the TA was the most affected muscle in most of the patients particularly during the activation burst in late swing (p<.0004). After medication (ON L-Dopa), the amplitude and timing of distal muscle activations became more similar to normal values, with the increase in EMG amplitude being dramatic in some patients. In the proximal muscles, the effects on EMG amplitude were less marked and prolonged activation often persisted even after the administration of L-Dopa.