Abstract
Gait deficits are a common feature of Parkinson’s disease (PD) and predictors of future motor and cognitive impairment. Understanding how muscle activity contributes to gait impairment and effects of therapeutic interventions on motor behaviour is crucial for identifying potential biomarkers and developing rehabilitation strategies. This article reviews sixteen studies that investigate the electromyographic (EMG) activity of lower limb muscles in people with PD during walking and reports on their quality. The weight of evidence establishing differences in motor activity between people with PD and healthy older adults (HOAs) is considered. Additionally, the effect of dopaminergic medication and deep brain stimulation (DBS) on modifying motor activity is assessed. Results indicated greater proximal and decreased distal activity of lower limb muscles during walking in individuals with PD compared to HOA. Dopaminergic medication was associated with increased distal lower limb muscle activity whereas subthalamic nucleus DBS increased activity of both proximal and distal lower limb muscles. Tibialis anterior was impacted most by the interventions. Quality of the studies was not strong, with a median score of 61%. Most studies investigated only distal muscles, involved small sample sizes, extracted limited EMG features and lacked rigorous signal processing. Few studies related changes in motor activity with functional gait measures. Understanding mechanisms underpinning gait impairment in PD is essential for development of personalised rehabilitative interventions. Recommendations for future studies include greater participant numbers, recording more functionally diverse muscles, applying multi-muscle analyses, and relating EMG to functional gait measures.
Highlights
Parkinson’s disease (PD) is a multisystem neurodegenerative disease with characteristic features present in both non-motor and motor domains[1]
No studies scored on Q9, which related to justification of sample size and only three studies discussed sampling methods (Q9) or attachment of electrodes
Results from this review indicate individuals with PD have decreased activity of distal lower limb muscles, plantarflexors, and increased activity of proximal lower limb muscles during walking compared to healthy older adults (HOAs)
Summary
Parkinson’s disease (PD) is a multisystem neurodegenerative disease with characteristic features present in both non-motor and motor domains[1]. The non-motor clinical manifestations include sensory impairments such as pain and tingling, depression, hyposmia and altered executive function[2]. The main motor symptoms are resting tremor, bradykinesia, rigidity, postural instability and gait disturbance[3]. This review is concerned with gait dysfunction and will focus on gait and related motor symptoms. Gait disturbance is characterised by slow shuffling steps[4], asymmetry[5] and high stride-to-stride variability[6,7]. The increased energy expenditure associated with dysfunctional gait makes even a short walk a major physical effort[8], thereby restricting mobility which impacts on quality of life. Fall risk is higher in people with PD9,10, which imposes a social and economic burden through hospitalisation[11] and subsequent health care costs[12,13]
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