Objective: To evaluate the role of movement amplitude and rate on spatiotemporal parameters and EMG response during a rhythmic and continuous finger-tapping paradigm in people with Parkinson’s disease (PD) and Freezing of Gait (FOG).

Background: As observed during gait, repetitive movement of the fingers is compromised in PD, especially in people who experience FOG (FOG+). Previous studies have suggested that there may be a core mechanism underlying the hastened motor behavior which may lead up to FOG. Previous EMG studies of FOG have only addressed gait.

Methods: Forty-eight people (22 healthy controls (HC), eighteen PD patients without FOG (NFOG) and 8 FOG+ performed flexion and extension of both index fingers for 30 seconds at a comfortable (Large) or small amplitude (Small = 66% of Large). Additionally, participants executed the movement at a comfortable (Normal) or fast rate (Fast = 133% of Normal). We assessed movement rate and amplitude and the iEMG signal of extensor digitorum (Ext) and first interosseous muscles. Only trials without any motor blocks were considered.

Results: The results showed that FOG+ are unable to increase the Ext recruitment level: no Amplitude effects were observed. In contrast, HC and NFOG increased the Ext EMG level in Large. The interosseous recruitment level responded similarly in all groups to both movement rate and amplitude. HC were also able to increase the movement rate during fast movement. Disparately, NFOG and FOG+ were able to increase the movement rate only when performing small amplitudes. All groups were able to regulate movement amplitude, i.e. produce larger amplitudes in Large during both Fast and Normal rates.

Conclusions: The results suggest a specific disturbance in the neural drive regulation in FOG+, since they were unable to recruit Ext properly when executing larger movement amplitude. PD patients have an impaired ability to combine movement amplitude and rate adaptation, especially when generating larger amplitudes.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-movement-rate-and-amplitude-on-repetitive-finger-motion-in-people-with-parkinsons-disease-and-freezing-of-gait/