Objective: Aim 1 was to compare rates of neuromuscular excitation during cycling at maximum pedaling speeds between people with Parkinson’s disease (PD) who are fast or slow. Aim 2 was to relate rates of neuromuscular excitation during cycling to performance on mobility tests in people with PD.

Background: Bradykinesia slows movement and affects the ability to perform activities of daily living in some PD. Gait studies have found that altered muscle activity contributes to these difficulties. Maximal rates of neuromuscular excitation are difficult to study during gait due to increased fall risk at high speeds. Stationary cycling is a model that enables the study of muscle activity in PD at high speeds safely, which may inform intervention work to address neuromuscular rate limiters of mobility.

Method: 18 adults with PD (67.9±8.1 years, 6.1±4.9 years since diagnosis, 4 females) completed the study. Electromyograms (EMG) were recorded from the vastus lateralis muscle during recumbent bicycling. Subjects cycled against the lowest resistance setting at 60 revolutions per minute (RPM) and as fast as possible to reach their peak cadence (mxRPM). EMG was normalized to peak EMG at 60 RPM. Rate of EMG rise (RER) was calculated as the slope of the rectified EMG. Subjects also performed the timed up and go (TUG) and four square step test (FSST) as quickly and safely as possible. PD groups were formed based on whether they could cycle ≥120 RPMs (PDfast) or not (PDslow). Mixed models were used to compare groups in mobility, mxRPM, and RER at mxRPM with cadence as a covariate. Spearman’s correlations were used to quantify relationships between mobility and RER.

Results: PDfast (n=10) had greater maximum pedaling speed (F=42.9, p<0.01) and lower TUG (F=11.6, p<0.01), and FSST (F=6.6, p=0.02) times than PDslow (n=8). PDfast had higher RER than PDslow (F=10.0, p<0.01). Correlations were significant (p<.05) for relationships between RER and FSST (ρ=-0.62), TUG (ρ=-0.53), and mxRPM (ρ=0.76).

Conclusion: People with PD with lower mxRPM also had poorer mobility performance and lower RER. Additionally, RER had moderate to strong relationships with mxRPM and mobility. Exercise to improve mxRPM may improve RER and mobility in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rate-of-neuromuscular-excitation-during-cycling-related-to-mobility-in-parkinsons-disease/