Forward leaning alters gait initiation only at extreme anterior postural positions

Recognition of walking directional intention employed ground reaction forces and center of pressure during gait initiation

BACKGROUND

Movement intentions are generally classified by Electroencephalogram (EEG) and have been used in gait initiation prediction. However, it is not easy to collect EEG data and practical in reality. Alternatively, ground reaction force (GRF) and the center of pressure (COP) is produced by the contact between the foot and the ground during a specific period of walking, which are the characteristics of evaluating gait performance RESEARCH QUESTION: The study aims to use a deep learning technique to recognize the data of the COP and GRF to classify straight walking and right turn. Second, the study aims to reveal gait characteristics that could replace EEG to predict walking directional intentions METHODS: Ten healthy male adults were instructed to stand on the force platform and self-selected to perform three conditions: standstill, straight walking, and right turn. The onset of gait initiation was evaluated by muscle activation of the right tibialis anterior, and EEG and the COP displacement evaluated the onset of gait intention. Subsequently, GRF and COP would be treated as features to classify the gait intention in the Long Short-Term Memory (LSTM) model.

RESULTS

The results revealed that the onset of EEG and the COP displacement initiation were statistically significant differences between straight walking and right turn. For the classification, the average accuracy of the LSTM model with GRF and COP as features reached the highest one, 94.79 %, depending on the heel- or toe-off of the swing leg. The results indicated that gait intentions could be classified based on the GRF and COP.

SIGNIFICANCE

The machine learning technique of LSTM with gait parameters can recognize the gait intention of changing walking orientation. Our model and approach would be expected to provide advanced predictions, such as exoskeleton control or pedestrian traffic flow.

Gait Initiation Impairment in Patients with Parkinson's Disease and Freezing of Gait

Freezing of gait (FOG) is a sudden episodic inability to produce effective stepping despite the intention to walk. It typically occurs during gait initiation (GI) or modulation and may lead to falls. We studied the anticipatory postural adjustments (imbalance, unloading, and stepping phase) at GI in 23 patients with Parkinson's disease (PD) and FOG (PDF), 20 patients with PD and no previous history of FOG (PDNF), and 23 healthy controls (HCs). Patients performed the task when off dopaminergic medications. The center of pressure (CoP) displacement and velocity during imbalance showed significant impairment in both PDNF and PDF, more prominent in the latter patients. Several measurements were specifically impaired in PDF patients, especially the CoP displacement along the anteroposterior axis during unloading. The pattern of segmental center of mass (SCoM) movements did not show differences between groups. The standing postural profile preceding GI did not correlate with outcome measurements. We have shown impaired motor programming at GI in Parkinsonian patients. The more prominent deterioration of unloading in PDF patients might suggest impaired processing and integration of somatosensory information subserving GI. The unaltered temporal movement sequencing of SCoM might indicate some compensatory cerebellar mechanisms triggering time-locked models of body mechanics in PD.

Separated center-of-pressure measurements reveal new characteristics of reduced anticipatory postural adjustments during gait initiation in patients with Parkinson's disease

Background and Objective: Accelerations, ground reaction force data, and other quantitative data obtained from kinematic analyses of gait initiation serve as measures of dyskinesia in patients with Parkinson's disease. The objective of this study was to determine whether a separate center of pressure information could reveal new characteristics of reduced anticipatory postural adjustments in patients with Parkinson's disease. Methods: Ten healthy elderly subjects and 10 patients with Parkinson's disease participated in this study. Motions at gait initiation in response to a light signal to begin the task were analyzed. Anticipatory postural adjustments were characterized using trunk acceleration data and center of pressure displacement data. Results: The separated center of pressure in patients with Parkinson's disease showed longer peak latency (p < .01) and larger peak magnitude (p < .01) in the stance leg than in the stepping leg. In patients with Parkinson's disease, the displacement peak latency of the stance leg center of pressure correlated negatively with the Timed Up and Go time (r = -0.46, p < .05), while displacement peak latency of the stepping leg center of pressure correlated negatively with Unified Parkinson's Disease Rating Scale (r=  -0.47, p < .05), and positively with Berg Balance Scale score (r = 0.50, p < .05). Conclusions: Patients with Parkinson's disease experience asymmetry between the stance leg and stepping leg at gait initiation. These findings may help clinicians understand the changes to motor function in patients with Parkinson's disease and suggest strategies for improved rehabilitation training.

Gait initiation in progressive supranuclear palsy: brain metabolic correlates

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Dysfunctional gait initiation in progressive supranuclear palsy relates to poor feedforward motor control.

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Hypometabolism of the caudate nucleus impairs programming of anticipatory postural adjustments.

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Thalamic hypometabolism correlates with the center of mass kinematic resultants of anticipatory postural adjustments.

The initiation of gait is a highly challenging task for the balance control system, and can be used to investigate the neural control of upright posture maintenance during whole-body movement. Gait initiation is a centrally-mediated motion achieved in a principled, controlled manner, including predictive mechanisms (anticipatory postural adjustments, APA) that destabilize the antigravitary postural set of body segments for the execution of functionally-optimized stepping. Progressive supranuclear palsy (PSP) is a neurodegenerative disease characterized by early impairment of balance and frequent falls. The neural correlates of postural imbalance and falls in PSP are largely unknown. We biomechanically assessed the APA at gait initiation (imbalance, unloading, and stepping phases) of 26 patients with PSP and 14 age-matched healthy controls. Fourteen of 26 enrolled patients were able to perform valid gait initiation trials. The influence of anthropometric and base-of-support measurements on the biomechanical outcome variables was assessed and removed. Biomechanical data were correlated with clinical findings and, in 11 patients, with brain metabolic abnormalities measured using positron emission tomography and 2-deoxy-2-[18F]fluoro-D-glucose. Patients with PSP showed impaired modulation of the center of pressure displacement for a proper setting of the center of mass momentum and subsequent efficient stepping. Biomechanical measurements correlated with “Limb motor” and “Gait and midline” subscores of the Progressive Supranuclear Palsy Rating Scale. Decreased regional glucose uptake in the caudate nucleus correlated with impaired APA programming. Hypometabolism of the caudate nucleus, supplementary motor area, cingulate cortex, thalamus, and midbrain was associated with specific biomechanical resultants of APA. Our findings show that postural instability at gait initiation in patients with PSP correlates with deficient APA production, and is associated with multiple and distinctive dysfunctioning of different areas of the supraspinal locomotor network. Objective biomechanical measures can help to understand fall-related pathophysiological mechanisms and to better monitor disease progression and new interventions.