Differences in the EMG pattern of leg muscle activation during locomotion in Parkinson's disease.

In this pilot study, EMG patterns of leg muscle activation were studied in five parkinsonian patients with (B1) and five without (B2) freezing. Gastrocnemius medialis (GM) and tibialis anterior (TA) activity was analysed, by means of surface electromyography (EMG), during treadmill walking at two different belt speeds. Both groups showed reduced GM activity and an overactive TA at the lower speed compared with controls. Upon increasing the speed, the B2 patients showed a marked GM response (increment index 100%), while a moderate change was observed in the B1 group. Poor recruitment of the GM characterises parkinsonian gait in general; this pattern is much more marked in parkinsonian patients with freezing of gait, who show a loss of GM adaptation to variation of locomotion speed.