Quadrupedal coordination of bipedal gait: implications for movement disorders

A New Compound-Limbs Paradigm: Integrating Upper-Limb Swing Improves Lower-Limb Stepping Intention Decoding From EEG

Brain-computer interface (BCI) systems based on spontaneous electroencephalography (EEG) hold the promise to implement human voluntary control of lower-extremity powered exoskeletons. However, current EEG-BCI paradigms do not consider the cooperation of upper and lower limbs during walking, which is inconsistent with natural human stepping patterns. To deal with this problem, this study proposed a stepping-matched human EEG-BCI paradigm that involved actions of both unilateral lower and contralateral upper limbs (also referred to as compound-limbs movement). Experiments were conducted in motor execution (ME) and motor imagery (MI) conditions to validate the feasibility. Common spatial pattern (CSP) proposed subject-specific CSP (SSCSP), and filter-bank CSP (FBCSP) methods were applied for feature extraction, respectively. The best average classification results based on SSCSP indicated that the accuracies of compound-limbs paradigms in ME and MI conditions achieved 89.02% ± 12.84% and 73.70% ± 12.47%, respectively. Although they were 2.03% and 5.68% lower than those of the single-upper-limb mode that does not match human stepping patterns, they were 24.30% and 11.02% higher than those of the single-lower-limb mode. These findings indicated that the proposed compound-limbs EEG-BCI paradigm is feasible for decoding human stepping intention and thus provides a potential way for natural human control of walking assistance devices.

A protocol to analyze the global literature on the clinical benefit of interlimb-coordinated intervention in gait recovery and the associated neurophysiological changes in patients with stroke

Background

Stroke is among the leading causes of disability of worldwide. Gait dysfunction is common in stroke survivors, and substantial advance is yet to be made in stroke rehabilitation practice to improve the clinical outcome of gait recovery. The role of the upper limb in gait recovery has been emphasized in the literature. Recent studies proposed that four limbs coordinated interventions, coined the term “interlimb-coordinated interventions,” could promote gait function by increasing the neural coupling between the arms and legs. A high-quality review is essential to examine the clinical improvement and neurophysiological changes following interlimb-coordinated interventions in patients with stroke.

Methods

Systematic review and meta-analysis will be conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The literature will be retrieved from the databases of OVID, MEDLINE, PubMed, Web of Science, EMBASE, and PsycINFO. Studies published in English over the past 15 years will be included. All of the clinical studies (e.g., randomized, pseudorandomized and non-randomized controlled trials, uncontrolled trials, and case series) that employed interlimb intervention and assessed gait function of patients with stroke will be included. Clinical functions of gait, balance, lower limb functions, and neurophysiologic changes are the outcome measures of interest. Statistical analyses will be performed using the Comprehensive Meta-Analysis version 3.

Discussion

The findings of this study will provide insight into the clinical benefits and the neurophysiological adaptations of the nervous system induced by interlimb-coordinated intervention in patients with stroke. This would guide clinical decision-making and the future development of targeted neurorehabilitation protocol in stroke rehabilitation to improve gait and motor function in patients with stroke. Increasing neuroplasticity through four-limb intervention might complement therapeutic rehabilitation strategies in this patient group. The findings could also be insightful for other cerebral diseases.

Synergy-based knee angle estimation using kinematics of thigh

BACKGROUND

Lower limb assistive devices have been developed to help amputees or stroke patients. To precisely mimic the required function, researchers focused on how to estimate/predict the required knee angle for knee devices.

RESEARCH QUESTION

The objective is to estimate the motion of the human knee joint during walking using the kinematics of wearer's thigh measured by a single Inertial Measurement Unit (IMU). The hypotheses are that the proposed method can precisely estimate knee angle and have good universality on different subjects, speeds and strides.

METHOD

8 healthy subjects walked on the level ground at three different speeds. An IMU mounted on the thigh was employed to collect the kinematic information of the thigh including angular velocities and accelerations. A long short-term memory (LSTM) neural network model was adopted to model intra-limb synergy between the motion of thigh and the knee joint. Such that with the trained LSTM model, the knee angle can be precisely predicted.

RESULTS

Compared with the existing studies, the proposed approach based on an LSTM model has better estimation performance. The average RMSE for eight subjects can be limited to 3.89°. The proposed method has speed and stride adaptability.

SIGNIFICANCE

The proposed method is promising to generate a desired and harmonious knee trajectory in line with thigh motion for assistive robotic devices.

Effects of Wnt5a overexpression in spinal cord injury

Accordingly to its known function in corticospinal tract (CST) developmental growth, previous reports have shown an inhibitory role of Wnt5a in CST regeneration after spinal cord injury (SCI). Interestingly, it has been subsequently demonstrated that Wnt5a also modulates the developmental growth of non‐CST axons and that different Wnt5a receptors are expressed in neurons, oligodendrocytes, NG2+ glial precursors and reactive microglia/macrophages and astrocytes after SCI. However, the role of Wnt5a in the response of these cell types, in the regeneration of non‐CST axons and in functional recovery after SCI is currently unknown. To evaluate this, rats were subjected to spinal cord contusion and injected with a lentiviral vector generated to overexpress Wnt5a. Histological analyses were performed in spinal cord sections processed for the visualization of myelin, oligodendrocytes, neurons, microglia/macrophages, astrocytes, NG2+ glial precursors and serotonergic axons. Motor and bladder function recovery were also assessed. Further advancing our knowledge on the role of Wnt5a in SCI, we found that, besides its previously reported functions, Wnt5a overexpression elicits a reduction on neuronal cell density, the accumulation of NG2+ glial precursors and the descending serotonergic innervation in the affected areas, along with impairment of motor and bladder function recovery after SCI.

Effects of pedunculopontine nucleus cholinergic lesion on gait and dyskinesia in hemiparkinsonian rats

Pedunculopontine nucleus (PPN) cholinergic neurons are implicated in freezing of gait in Parkinson's disease (PD) and motor stereotypy in normal animals, but the causal role of these neurons on specific gait parameters and treatment-induced dyskinesia remains speculative. Therefore, we examined whether selective cholinergic lesion of the rostral PPN affects PD motor and gait deficits, L-DOPA-induced dyskinesia and motor improvement, and DA-agonist-induced dyskinesia. Sprague-Dawley rats were assigned to one unilaterally lesioned group: Sham lesion, PPN cholinergic lesion with diphtheria urotensin II fusion toxin, medial forebrain bundle dopamine lesion with 6-hydroxydopamine, or dual acetylcholine and dopamine lesion. We used gait analysis and forepaw adjusting steps to examine PD gait and motor deficits. Forepaw adjusting steps were also used to assess motor improvement with L-DOPA treatment. The abnormal involuntary movements scale measured L-DOPA and dopamine D1- and D2-receptor agonist-induced dyskinesia. Lesions, verified via tyrosine hydroxylase and choline acetyltransferase immunohistochemistry reduced an average of 95% of nigral dopamine neurons and 80% of PPN cholinergic neurons, respectively. Rats receiving acetylcholine and dual lesion demonstrated enhanced freezing, and acetylcholine lesioned rats exhibited increased print area and stand index. Dopamine and dual lesion produced similar forepaw adjusting steps task on and off L-DOPA. Relative to DA lesioned rats, dual lesioned rats displayed reduced L-DOPA and DA agonist-induced dyskinesia at specific time points. Our results indicate that PPN cholinergic neurons affect gait parameters related to postural stability. Therefore, therapeutically targeting PPN cholinergic neurons could reduce intractable postural instability in PD without affecting motor benefits or side effects of L-DOPA treatment.

Synchronized Tactile Stimulation on Upper Limbs Using a Wearable Robot for Gait Assistance in Patients With Parkinson's Disease

This study aimed to investigate whether using a wearable robot applying interactive rhythmic stimulation on the upper limbs of patients with Parkinson's disease (PD) could affect their gait. The wearable robot presented tactile stimuli on the patients' upper limbs, which was mutually synchronized with the swing of their upper limbs. We conducted an evaluation experiment with PD patients (n = 30, Modified Hoehn-Yahr = 1-3, on-state) to investigate the assistance effect by the robot and the immediate after-effect of intervention. The participants were instructed to walk 30 m under four different conditions: (1) not wearing the robot before the intervention (Pre-condition), (2) wearing the robot without the rhythm assistance (RwoA condition), (3) wearing the robot with rhythm assistance (RwA condition), and (4) not wearing the robot immediately after the intervention (Post-condition). These conditions were conducted in this order over a single day. The third condition was performed three times and the others, once. The arm swing amplitude, stride length, and velocity were increased in the RwA condition compared to the RwoA condition. The coefficient of variance (CV) of the stride duration was decreased in the RwA condition compared to the RwoA condition. These results revealed that the assistance by the robot increased the gait performance of PD patients. In addition, the stride length and velocity were increased and the stride duration CV was decreased in the Post-condition compared to the Pre-condition. These results show that the effect of robot assistance on the patient's gait remained immediately after the intervention. These findings suggest that synchronized rhythmic stimulation on the upper limbs could influence the gait of PD patients and that the robot may assist with gait rehabilitation in these patients.

Interlimb coupling in poststroke rehabilitation: a pilot randomized controlled trial

Background: The interlimb coupling, coordination between the limbs, gets hampered in post-stroke hemiparesis. Most of the poststroke motor regimes primarily focus on the more affected limb.Objectives: To develop an interlimb coupling protocol and assess its feasibility and effect on motor recovery, gait and disability among post-stroke subjects.Design: A pilot randomized controlled, doubled blinded trialSetting: A rehabilitation instituteMethods: 50 post-stroke (> 6 months) hemiparetic subjects (Brunnstrom recovery stage ≥ 3) were randomly divided into experimental (n=26) and control (n=24) groups. The 8-week experimental intervention (3 sessions of 1 hour each, per week) comprised activities demanding coordinated, alternate, and rhythmic use of the affected as well as the less-affected limbs. The outcome measures were feasibility of activities, Fugl-Meyer assessment (FMA), Rivermead visual gait assessment (RVGA), Functional ambulation category (FAC) and modified Rankin scale (mRS).Results: The experimental protocol was found to be feasible by the participants. Post intervention, the experimental group exhibited highly significant difference for FMA (mean difference = 7.12, 95% CI = 5.71 - 8.53, p < 0.001), RVGA reduction (mean difference = - 6.32, 95% CI = 7.51 - 5.13, p < 0.001), and median FAC enhancement (p < 0.001) in comparison to the controls. However, the median mRS level of experimental group did not change significantly (p = 0.056) when compared with the controls.Conclusions: The interlimb coupling training, a feasible program may enhance recovery of the upper and lower limbs and gait in stroke. Further definitive randomized trials are warranted to validate the present findings.

Deficit of Motor Skill Acquisition on the Upper Limb Ipsilesional to the Injured Hemisphere in Individuals with Stroke

Background

Movement deficits in limbs ipsilesional to the damaged hemisphere in individuals with stroke have been established through various motor tasks. Nevertheless, there has been little evidence regarding hindrance of motor skill acquisition on the ipsilesional limb in patients with stroke. Therefore, we attempted to demonstrate whether the characteristics of ipsilesional deficits involved motor learning insufficiency in stroke survivors with unilateral brain damage.

Material/Methods

Thirty-six participants (18 patients with stroke and 18 normal individuals) were recruited. Patients with stroke performed a visuo-spatial tracking task in the upper limb ipsilesional to the injured hemisphere, and normal participants did the same task with the upper limb matched for the same side. The participants were required to track a target sine wave as accurately as possible while the wave was displayed on the computer screen for 15 seconds. An accuracy index was calculated for each of the trials.

Results

We found that motor skill learning improved in both stroke and normal groups with repetitive practice. However, the normal group exhibited greater motor skill acquisition than in comparison the stroke group for motor skill improvement. Statistical analyses revealed significant differences in time effects and time x group interactions.

Conclusions

Our findings provide evidence that individuals with stroke might have difficulty in performing visuo-spatial movements and acquiring motor skills with the ipsilateral upper limb. Improvement of ipsilesional limb function increases self-care activity in daily life. Therefore, we recommend that clinicians adopt remedial strategies for ipsilesional limbs.

Voluntary ambulation using voluntary upper limb muscle activity and Hybrid Assistive Limb® (HAL®) in a patient with complete paraplegia due to chronic spinal cord injury: A case report

Context: We sought to describe our experience with the Hybrid Assistive Limb® (HAL®) for active knee extension and voluntary ambulation with remaining muscle activity in a patient with complete paraplegia after spinal cord injury. Findings: A 30-year-old man with complete paraplegia used the HAL® for 1 month (10 sessions) using his remaining muscle activity, including hip flexor and upper limb activity. Electromyography was used to evaluate muscle activity of the gluteus maximus, tensor fascia lata, quadriceps femoris, and hamstring muscles in synchronization with the Vicon motion capture system. A HAL® session included a knee extension session with the hip flexor and voluntary gait with upper limb activity. After using the HAL® for one month, the patient's manual muscle hip flexor scores improved from 1/5 to 2/5 for the right and from 2/5 to 3/5 for the left knee, and from 0/5 to 1/5 for the extension of both knees. Conclusion/clinical relevance: Knee extension sessions with HAL®, and hip flexor and upper-limb-triggered HAL® ambulation seem a safe and feasible option in a patient with complete paraplegia due to spinal cord injury.

Synergistic influences of sensory and central stimuli on non-voluntary rhythmic arm movements

In recent years, neuromodulation of the cervical spinal circuitry has become an area of interest for investigating rhythmogenesis of the human spinal cord and interaction between cervical and lumbosacral circuitries, given the involvement of rhythmic arm muscle activity in many locomotor tasks. We have previously shown that arm muscle vibrostimulation can elicit non-voluntary upper limb oscillations in unloading body conditions. Here we investigated the excitability of the cervical spinal circuitry by applying different peripheral and central stimuli in healthy humans. The rationale for applying combined stimuli is that the efficiency of only one stimulus is generally limited. We found that low-intensity electrical stimulation of the superficial arm median nerve can evoke rhythmic arm movements. Furthermore, the movements were enhanced by additional peripheral stimuli (e.g., arm muscle vibration, head turns or passive rhythmic leg movements). Finally, low-frequency transcranial magnetic stimulation of the motor cortex significantly facilitated rhythmogenesis. The findings are discussed in the general framework of a brain-spinal interface for developing adaptive central pattern generator-modulating therapies.

Effect of cervicolumbar coupling on spinal reflexes during cycling after incomplete spinal cord injury

Spinal networks in the cervical and lumbar cord are actively coupled during locomotion to coordinate arm and leg activity. The goals of this project were to investigate the intersegmental cervicolumbar connectivity during cycling after incomplete spinal cord injury (iSCI) and to assess the effect of rehabilitation training on improving reflex modulation mediated by cervicolumbar pathways. Two studies were conducted. In the first, 22 neurologically intact (NI) people and 10 people with chronic iSCI were recruited. The change in H-reflex amplitude in flexor carpi radialis (FCR) during leg cycling and H-reflex amplitude in soleus (SOL) during arm cycling were investigated. In the second study, two groups of participants with chronic iSCI underwent 12 wk of cycling training: one performed combined arm and leg cycling (A&L) and the other legs only cycling (Leg). The effect of training paradigm on the amplitude of the SOL H-reflex was assessed. Significant reduction in the amplitude of both FCR and SOL H-reflexes during dynamic cycling of the opposite limbs was found in NI participants but not in participants with iSCI. Nonetheless, there was a significant reduction in the SOL H-reflex during dynamic arm cycling in iSCI participants after training. Substantial improvements in SOL H-reflex properties were found in the A&L group after training. The results demonstrate that cervicolumbar modulation during rhythmic movements is disrupted in people with chronic iSCI; however, this modulation is restored after cycling training. Furthermore, involvement of the arms simultaneously with the legs during training may better regulate the leg spinal reflexes.

NEW & NOTEWORTHY This work systematically demonstrates the disruptive effect of incomplete spinal cord injury on cervicolumbar coupling during rhythmic locomotor movements. It also shows that the impaired cervicolumbar coupling could be significantly restored after cycling training. Actively engaging the arms in rehabilitation paradigms for the improvement of walking substantially regulates the excitability of the lumbar spinal networks. The resulting regulation may be better than that obtained by interventions that focus on training of the legs only.

A multidirectional gravity-assist algorithm that enhances locomotor control in patients with stroke or spinal cord injury

Gait recovery after neurological disorders requires remastering the interplay between body mechanics and gravitational forces. Despite the importance of gravity-dependent gait interactions and active participation for promoting this learning, these essential components of gait rehabilitation have received comparatively little attention. To address these issues, we developed an adaptive algorithm that personalizes multidirectional forces applied to the trunk based on patient-specific motor deficits. Implementation of this algorithm in a robotic interface reestablished gait dynamics during highly participative locomotion within a large and safe environment. This multidirectional gravity-assist enabled natural walking in nonambulatory individuals with spinal cord injury or stroke and enhanced skilled locomotor control in the less-impaired subjects. A 1-hour training session with multidirectional gravity-assist improved locomotor performance tested without robotic assistance immediately after training, whereas walking the same distance on a treadmill did not ameliorate gait. These results highlight the importance of precise trunk support to deliver gait rehabilitation protocols and establish a practical framework to apply these concepts in clinical routine.

Reliability and validity of the inertial sensor-based Timed "Up and Go" test in individuals affected by stroke

The instrumented Timed "Up and Go" test (iTUG) has the potential for playing an important role in providing clinically useful information regarding an individual's balance and mobility that cannot be derived from the original single-outcome Timed "Up and Go" test protocol. The purpose of this study was to determine the reliability and validity of the iTUG using body-fixed inertial sensors in people affected by stroke. For test-retest reliability analysis, 14 individuals with stroke and 25 nondisabled elderly patients were assessed. For validity analysis, an age-matched comparison of 12 patients with stroke and 12 nondisabled controls was performed. Out of the 14 computed iTUG metrics, the majority showed excellent test-retest reliability expressed by high intraclass correlation coefficients (range 0.431-0.994) together with low standard error of measurement and smallest detectable difference values. Bland-Altman plots demonstrated good agreement between two repeated measurements. Significant differences between patients with stroke and nondisabled controls were found in 9 of 14 iTUG parameters analyzed. Consequently, these results warrant the future application of the inertial sensor-based iTUG test for the assessment of physical deficits poststroke in longitudinal study designs.

Voluntary Ambulation by Upper Limb-Triggered HAL® in Patients with Complete Quadri/Paraplegia Due to Chronic Spinal Cord Injury

Patients with complete paraplegia after spinal cord injury (SCI) are unable to stand or walk on their own. Standing exercise decreases the risk of decubitus ulcers, osteoporosis, and joint deformities in patients with SCI. Conventional gait training for complete paraplegia requires excessive upper limb usage for weight bearing and is difficult in cases of complete quadriplegia. The purpose of this study was to describe voluntary ambulation triggered by upper limb activity using the Hybrid Assistive Limb® (HAL) in patients with complete quadri/paraplegia after chronic SCI. Four patients (3 men, 1 woman) were enrolled in this study. The mean patient age ± standard deviation was 37.2 ± 17.8 (range, 20–67) years. Clinical evaluation before intervention revealed the following findings: case 1, neurological level C6, American Spinal Cord Injury Association impairment scale (AIS) grade B; case 2, T6, AIS A; case 3, T10 AIS A; and case 4, T11, AIS A. The HAL intervention consisted of 10 sessions. Each HAL session lasted 60–90 min. The HAL electrodes for hip and knee flexion-extension were placed on the anterior and posterior sides of the upper limbs contralaterally corresponding to each of the lower limbs. Surface electromyography (EMG) was used to evaluate muscle activity of the tensor fascia lata and quadriceps femoris (Quad) in synchronization with a Vicon motion capture system. The modified Ashworth scale (mAs) score was also evaluated before and after each session. All participants completed all 10 sessions. Cases 1, 2, and 3 demonstrated significant decreases in mAs score after the sessions compared to pre-session measurements. In all cases, EMG before the intervention showed no apparent activation in either Quad. However, gait phase dependent activity of the lower limb muscles was seen during voluntarily triggered ambulation driven by upper limb muscle activities. In cases 3 and 4, active contraction in both Quads was observed after intervention. These findings suggest that upper-limb-triggered HAL ambulation is a safe and feasible option for rehabilitation in patients with complete quadri/paraplegia caused by chronic SCI.

Split-arm swinging: the effect of arm swinging manipulation on interlimb coordination during walking

Human locomotion is defined by bilateral coordination of gait (BCG) and shared features with the fore-hindlimb coordination of quadrupeds. The objective of the present study is to explore the influence of arm swinging (AS) on BCG. Sixteen young, healthy individuals (eight women; eight right motor-dominant, eight left-motor dominant) participated. Participants performed 10 walking trials (2 min). In each of the trials AS was unilaterally manipulated (e.g., arm restriction, weight on the wrist), bilaterally manipulated, or not manipulated. The order of trials was random. Walking trials were performed on a treadmill. Gait kinematics were recorded by a motion capture system. Using feedback-controlled belt speed allowed the participants to walk at a self-determined gait speed. Effects of the manipulations were assessed by AS amplitudes and the phase coordination index (PCI), which quantifies the left-right anti-phased stepping pattern. Most of the AS manipulations caused an increase in PCI values (i.e., reduced lower limb coordination). Unilateral AS manipulation had a reciprocal effect on the AS amplitude of the other arm such that, for example, over-swinging of the right arm led to a decrease in the AS amplitude of the left arm. Side of motor dominance was not found to have a significant impact on PCI and AS amplitude. The present findings suggest that lower limb BCG is markedly influenced by the rhythmic AS during walking. It may thus be important for gait rehabilitation programs targeting BCG to take AS into account.NEW & NOTEWORTHY Control mechanisms for four-limb coordination in human locomotion are not fully known. To study the influence of arm swinging (AS) on bilateral coordination of the lower limbs during walking, we introduced a split-AS paradigm in young, healthy adults. AS manipulations caused deterioration in the anti-phased stepping pattern and impacted the AS amplitudes for the contralateral arm, suggesting that lower limb coordination is markedly influenced by the rhythmic AS during walking.

Bilateral Reflex Fluctuations during Rhythmic Movement of Remote Limb Pairs

The modulation of spinal cord excitability during rhythmic limb movement reflects the neuronal coordination underlying actions of the arms and legs. Integration of network activity in the spinal cord can be assessed by reflex variability between the limbs, an approach so far very little studied. The present work addresses this question by eliciting Hoffmann (H-) reflexes in both limbs to assess if common drive onto bilateral pools of motoneurons influence spinal cord excitability simultaneously or with a delay between sides. A cross-covariance (CCV) sequence between reflexes in both arms or legs was evaluated under conditions providing common drive bilaterally through voluntary muscle contraction and/or rhythmic movement of the remote limbs. For H-reflexes in the flexor carpi radialis (FCR) muscle, either contraction of the FCR or leg cycling induced significant reduction in the amplitude of the peak at the zero lag in the CCV sequence, indicating independent variations in spinal excitability between both sides. In contrast, for H-reflexes in the soleus (SO) muscle, arm cycling revealed no reduction in the amplitude of the peak in the CCV sequence at the zero lag. This suggests a more independent control of the arms compared with the legs. These results provide new insights into the organization of human limb control in rhythmic activity and the behavior of bilateral reflex fluctuations under different motor tasks. From a functional standpoint, changes in the co-variability might reflect dynamic adjustments in reflex excitability that are subsumed under more global control features during locomotion.

The neural control of interlimb coordination during mammalian locomotion

Neuronal networks within the spinal cord directly control rhythmic movements of the arms/forelimbs and legs/hindlimbs during locomotion in mammals. For an effective locomotion, these networks must be flexibly coordinated to allow for various gait patterns and independent use of the arms/forelimbs. This coordination can be accomplished by mechanisms intrinsic to the spinal cord, somatosensory feedback from the limbs, and various supraspinal pathways. Incomplete spinal cord injury disrupts some of the pathways and structures involved in interlimb coordination, often leading to a disruption in the coordination between the arms/forelimbs and legs/hindlimbs in animal models and in humans. However, experimental spinal lesions in animal models to uncover the mechanisms coordinating the limbs have limitations due to compensatory mechanisms and strategies, redundant systems of control, and plasticity within remaining circuits. The purpose of this review is to provide a general overview and critical discussion of experimental studies that have investigated the neural mechanisms involved in coordinating the arms/forelimbs and legs/hindlimbs during mammalian locomotion.

Implementation of a smartphone as a wireless gyroscope platform for quantifying reduced arm swing in hemiplegie gait with machine learning classification by multilayer perceptron neural network

Natural gait consists of synchronous and rhythmic patterns for both the lower and upper limb. People with hemiplegia can experience reduced arm swing, which can negatively impact the quality of gait. Wearable and wireless sensors, such as through a smartphone, have demonstrated the ability to quantify various features of gait. With a software application the smartphone (iPhone) can function as a wireless gyroscope platform capable of conveying a gyroscope signal recording as an email attachment by wireless connectivity to the Internet. The gyroscope signal recordings of the affected hemiplegic arm with reduced arm swing arm and the unaffected arm are post-processed into a feature set for machine learning. Using a multilayer perceptron neural network a considerable degree of classification accuracy is attained to distinguish between the affected hemiplegic arm with reduced arm swing arm and the unaffected arm.

Does Nordic Walking restore the temporal organization of gait variability in Parkinson's disease?

BACKGROUND

Gait disorders of Parkinson's disease (PD) are characterized by the breakdown of the temporal organization of stride duration variability that was tightly associated to dynamic instability in PD. Activating the upper body during walking, Nordic Walking (NW) may be used as an external cueing to improve spatiotemporal parameters of gait, such as stride length or gait variability, in PD. The aim of this study was to evaluate the beneficial effects of NW on temporal organization of gait variability and spatiotemporal gait variables in PD.

METHODS

Fourteen mild to moderate PD participants and ten age-matched healthy subjects performed 2 × 12 min overground walking sessions (with and without pole in a randomized order) at a comfortable speed. Gait speed, cadence, step length and temporal organization (i.e. long-range autocorrelations; LRA) of stride duration variability were studied on 512 consecutive gait cycles using a unidimensional accelerometer placed on the malleola of the most affected side in PD patients and of the dominant side in healthy controls. The presence of LRA was determined using the Rescaled Range Analysis (Hurst exponent) and the Power Spectral Density (α exponent). To assess NW and disease influences on gait, paired t-tests, Z-score and a two-way (pathological condition x walking condition) ANOVA repeated measure were used.

RESULTS

Leading to significant improvement of LRA, NW enhances step length and reduces gait cadence without any change in gait speed in PD. Interestingly, LRA and step length collected from the NW session are similar to that of the healthy population.

CONCLUSION

This cross-sectional controlled study demonstrates that NW may constitute a powerful way to struggle against the randomness of PD gait and the typical gait hypokinesia. Involving a voluntary intersegmental coordination, such improvement could also be due to the upper body rhythmic movements acting as rhythmical external cue to bypass their defective basal ganglia circuitries.

ETHICS COMMITTEE'S REFERENCE NUMBER

B403201318916 TRIAL REGISTRATION: NCT02419768.

Rhythmic wrist movements facilitate the soleus H-reflex and non-voluntary air-stepping in humans

Neural coupling between the upper and lower limbs during human walking is supported by modulation of cross-limb reflexes and the presence of rhythmic activity in the proximal arm muscles. Nevertheless, the involvement of distal arm muscles in cyclic movements and sensorimotor neuromodulation is also suggested given their step-synchronized activation in many locomotor-related tasks (e.g., swimming, skiing, climbing, cycling, crawling, etc.). Here we investigated the effect of rhythmic wrist movements, separately and in conjunction with arm swinging, on the characteristics of non-voluntary cyclic leg movements evoked by muscle vibration in a gravity neutral position and on the soleus H-reflex of the stationary legs. For the H-reflex modulation, five conditions were compared: stationary arms, voluntary alternating upper limb swinging, combined upper limb and wrist motion, wrist movements only and motion of the upper limbs with addition of load. Rhythmic wrist movements significantly facilitated the amplitude of non-voluntary leg oscillations, including ankle joint oscillations, and the H-reflex. The latter effect was related to rhythmicity of wrist motion rather than to a simple extra tension in the upper limb muscles (a kind of the Jendrassik manoeuvre) since adding resistance to arm oscillations (without flexion-extension in the wrist joint) had an opposite inhibitory effect on the H-reflex. Our results further support the existence of connections between the distal parts of the upper and lower extremities at the neural level, suggesting that wrist joint movements can be an important component of motor neurorehabilitation.

Assessment of Gait Therapy Effectiveness in Patients with Parkinson's Disease on the Basis of Three-Dimensional Movement Analysis

Objective

The aim of this study was to assess the effect of physical exercise on gait pattern disorders, based on three-dimensional gait analysis in the sagittal plane in a group of people with Parkinson’s disease (PD).

Methods

Thirty-two subjects with PD (14 women and 18 men; age: 50–75 years) were qualified for the study, which ran for 3 weeks and included 18 therapeutic sessions. Thirty-five control subjects were included in the research (13 women and 19 men; age: 52–77 years). Gait analysis using the Vicon 3D system took place in the Biokinetics Laboratory. The research group was tested before and after treatment, and the control group was tested once.

Results

Comparing the average peak angle changes and average standard time results (% gait cycle) corresponding with angles of movement in the lumbar spine, cervical spine, elbow joint, and shoulder joint, statistically significant changes were observed. The study results are indicative of differences in spatiotemporal parameters and angular changes in gait for both groups. After therapeutic treatment, we observed improvement in the angular range of changes in thorax tilting, but there were no difference between the most affected and less affected side. For the cervical spine, a significant reduction in flexion during dual support was observed. The angular range of changes in shoulder joint was significant only in less affected shoulder during the initial contact (F1), terminal stance (F4), and terminal stance (F8) phases of gait (p < 0.05). After therapeutic treatment, significant angle and setting changes in the most affected limb of the elbow joint occurred during the initial contact and terminal swing phases (F1, F8). In the terminal stance phase (F4), an increase in range of motion by about ±4° was observed (p < 0.05).

Conclusion

Exercise therapy slightly increased the range of movement in the examined joints of PD’s patients. Results of pathological walking patterns occurring prior to treatment improved after treatment and moved closer to the physiological gait pattern.

Human cervical spinal cord circuitry activated by tonic input can generate rhythmic arm movements

The coordination between arms and legs during human locomotion shares many features with that in quadrupeds, yet there is limited evidence for the central pattern generator for the upper limbs in humans. Here we investigated whether different types of tonic stimulation, previously used for eliciting stepping-like leg movements, may evoke nonvoluntary rhythmic arm movements. Twenty healthy subjects participated in this study. The subject was lying on the side, the trunk was fixed, and all four limbs were suspended in a gravity neutral position, allowing unrestricted low-friction limb movements in the horizontal plane. The results showed that peripheral sensory stimulation (continuous muscle vibration) and central tonic activation (postcontraction state of neuronal networks following a long-lasting isometric voluntary effort, Kohnstamm phenomenon) could evoke nonvoluntary rhythmic arm movements in most subjects. In ∼40% of subjects, tonic stimulation elicited nonvoluntary rhythmic arm movements together with rhythmic movements of suspended legs. The fact that not all participants exhibited nonvoluntary limb oscillations may reflect interindividual differences in responsiveness of spinal pattern generation circuitry to its activation. The occurrence and the characteristics of induced movements highlight the rhythmogenesis capacity of cervical neuronal circuitries, complementing the growing body of work on the quadrupedal nature of human gait.

Comparative gait initiation kinematics between simulated unilateral and bilateral ankle hypomobility: Does bilateral constraint improve speed performance?

Improvement of motor performance in unilateral upper limb motor disability has been shown when utilizing inter-limb coupling strategies during physical rehabilitation. This suggests that 'default' bilateral central motor commands are facilitated. Here, we tested whether this bilateral motor control principle may be generalized to the lower limbs during gait initiation, which involves alternate bilateral actions. Disability was simulated by strapping to produce ankle hypomobility. Healthy adult subjects initiated gait at a self-paced speed with no ankle constraint (control), or with the stance, swing or bilateral ankles strapped. The duration of the anticipatory postural adjustments lengthened and the center of mass instantaneous progression velocity at foot-off decreased when the ankle was strapped. During the step execution phase, progression velocity at foot-contact was higher when both ankles were strapped compared to unilateral strapping of the stance ankle. These findings suggest that bilateral central motor commands are favored during walking tasks. Indeed, unilateral constraint of the stance ankle should compel the central nervous system to adapt specific commands to the constraint and normal sides whereas the 'default' bilateral motor commands would be utilized when both ankles are strapped leading to better kinematics performance. Bilateral in-phase upper limb coordination and bilateral alternating lower limb locomotor movements may share similar control mechanisms.

Motor automaticity in Parkinson's disease

Bradykinesia is the most important feature contributing to motor difficulties in Parkinson's disease (PD). However, the pathophysiology underlying bradykinesia is not fully understood. One important aspect is that PD patients have difficulty in performing learned motor skills automatically, but this problem has been generally overlooked. Here we review motor automaticity associated motor deficits in PD, such as reduced arm swing, decreased stride length, freezing of gait, micrographia and reduced facial expression. Recent neuroimaging studies have revealed some neural mechanisms underlying impaired motor automaticity in PD, including less efficient neural coding of movement, failure to shift automated motor skills to the sensorimotor striatum, instability of the automatic mode within the striatum, and use of attentional control and/or compensatory efforts to execute movements usually performed automatically in healthy people. PD patients lose previously acquired automatic skills due to their impaired sensorimotor striatum, and have difficulty in acquiring new automatic skills or restoring lost motor skills. More investigations on the pathophysiology of motor automaticity, the effect of L-dopa or surgical treatments on automaticity, and the potential role of using measures of automaticity in early diagnosis of PD would be valuable.

Effect of motor training involving the less-affected side (MTLA) in post-stroke subjects: a pilot randomized controlled trial

INTRODUCTION

Poststroke, less-severe motor impairment occurs on the ipsilesional side of body. The objective of the present study was to evaluate the effectiveness of the motor training involving the less-affected side (MTLA) in stroke.

METHODS

This was a randomized, controlled, double-blinded pilot study conducted in the occupational therapy unit of a rehabilitation Institute. A convenience sample of 35 stroke subjects (mean poststroke duration, 28.76 weeks) was randomized into two groups (the experimental group: 17 and control group: 18). Thirty-two participants completed the entire study protocol. The experimental group and control group were provided MTLA and neurophysiological-based conventional therapy respectively. Both the groups received 24 treatment sessions (60 minutes each) over the period of two months. The Affected side was assessed using Brunnstrom recovery stage (BRS) and Fugl-Meyer assessment (FMA) whereas the less-affected side was evaluated by Minnesota manual dexterity test (MMDT), Purdue peg board test (PPBT) and Manual Muscle Testing (MMT).

RESULTS

Postintervention, the less-affected side of experimental group demonstrated significant improvement for MMDT (P = 0.003), PPBT (P = 0.01) and MMT (P <  0.001 to 0.043) in comparison to the control group. Further, as compared to the control group, the experimental group exhibited positive significant change for the measure of affected side [BRS (P <  0.001) and FMA (P <  0.001 to 0.03)] at post assessment.

CONCLUSION

MTLA enhanced the muscle strength, dexterity and coordination of the less-affected side as well as the motor recovery of the affected side in poststroke hemiparetic subjects.

Tapping into rhythm generation circuitry in humans during simulated weightlessness conditions

An ability to produce rhythmic activity is ubiquitous for locomotor pattern generation and modulation. The role that the rhythmogenesis capacity of the spinal cord plays in injured populations has become an area of interest and systematic investigation among researchers in recent years, despite its importance being long recognized by neurophysiologists and clinicians. Given that each individual interneuron, as a rule, receives a broad convergence of various supraspinal and sensory inputs and may contribute to a vast repertoire of motor actions, the importance of assessing the functional state of the spinal locomotor circuits becomes increasingly evident. Air-stepping can be used as a unique and important model for investigating human rhythmogenesis since its manifestation is largely facilitated by a reduction of external resistance. This article aims to provide a review on current issues related to the “locomotor” state and interactions between spinal and supraspinal influences on the central pattern generator (CPG) circuitry in humans, which may be important for developing gait rehabilitation strategies in individuals with spinal cord and brain injuries.

Normative data for arm swing asymmetry: how (a)symmetrical are we?

Arm swing asymmetry during gait may be a sensitive sign for early Parkinson's disease. There is only very limited information about how much asymmetry can be considered to be physiological. To assess the normal range of arm swing asymmetry, we investigated 60 healthy subjects. The influence of age, gender, and additional mental tasks (dual-tasking) on arm swing asymmetry was assessed. Limb kinematics of 60 healthy persons in three age groups (between 40 and 75 years) were measured with an ultrasound motion capture system while subjects walked on a treadmill. Treadmill velocity was varied (3 steps) and mental loads (2 different tasks) were applied in different trials. Additionally, a group of 7 patients with early Parkinson's disease was investigated. Arm swing amplitude as well as arm swing asymmetry varied considerably in the healthy subjects. Elderly subjects swung their arms more than younger participants. Only the more demanding mental load caused a significant asymmetry, i.e., arm swing was reduced on the right side. In the patient group, asymmetry was considerably higher and even more enhanced by mental loads. Our data indicate that an asymmetry index above 50 (i.e., one side has twice the amplitude of the other) may be considered abnormal. Evaluation of arm swing asymmetry may be used as part of a test battery for early Parkinson's disease. Such testing may become even more important when disease-modifying drugs become available for Parkinson's disease.

Dynamic control of posture across locomotor tasks

Successful locomotion depends on postural control to establish and maintain appropriate postural orientation of body segments relative to one another and to the environment and to ensure dynamic stability of the moving body. This article provides a framework for considering dynamic postural control, highlighting the importance of coordination, consistency, and challenges to postural control posed by various locomotor tasks, such as turning and backward walking. The impacts of aging and various movement disorders on postural control are discussed broadly in an effort to provide a general overview of the field and recommendations for assessment of dynamic postural control across different populations in both clinical and research settings. Suggestions for future research on dynamic postural control during locomotion also are provided and include discussion of opportunities afforded by new and developing technologies, the need for long-term monitoring of locomotor performance in everyday activities, gaps in our knowledge of how targeted intervention approaches modify dynamic postural control, and the relative paucity of literature regarding dynamic postural control in movement disorder populations other than Parkinson's disease.

Novel multi-system functional gains via task specific training in spinal cord injured male rats

Locomotor training (LT) after spinal cord injury (SCI) is a rehabilitative therapy used to enhance locomotor recovery. There is evidence, primarily anecdotal, also associating LT with improvements in bladder function and reduction in some types of SCI-related pain. In the present study, we determined if a step training paradigm could improve outcome measures of locomotion, bladder function, and pain/allodynia. After a T10 contusive SCI trained animals (adult male Wistar rats), trained animals began quadrupedal step training beginning 2 weeks post-SCI for 1 h/day. End of study experiments (3 months of training) revealed significant changes in limb kinematics, gait, and hindlimb flexor-extensor bursting patterns relative to non-trained controls. Importantly, micturition function, evaluated with terminal transvesical cystometry, was significantly improved in the step trained group (increased voiding efficiency, intercontraction interval, and contraction amplitude). Because both SCI and LT affect neurotrophin signaling, and neurotrophins are involved with post-SCI plasticity in micturition pathways, we measured bladder neurotrophin mRNA. Training regulated the expression of nerve growth factor (NGF) but not BDNF or NT3. Bladder NGF mRNA levels were inversely related to bladder function in the trained group. Monitoring of overground locomotion and neuropathic pain throughout the study revealed significant improvements, beginning after 3 weeks of training, which in both cases remained consistent for the study duration. These novel findings, improving non-locomotor in addition to locomotor functions, demonstrate that step training post-SCI could contribute to multiple quality of life gains, targeting patient-centered high priority deficits.

Locomotor-like leg movements evoked by rhythmic arm movements in humans

Motion of the upper limbs is often coupled to that of the lower limbs in human bipedal locomotion. It is unclear, however, whether the functional coupling between upper and lower limbs is bi-directional, i.e. whether arm movements can affect the lumbosacral locomotor circuitry. Here we tested the effects of voluntary rhythmic arm movements on the lower limbs. Participants lay horizontally on their side with each leg suspended in an unloading exoskeleton. They moved their arms on an overhead treadmill as if they walked on their hands. Hand-walking in the antero-posterior direction resulted in significant locomotor-like movements of the legs in 58% of the participants. We further investigated quantitatively the responses in a subset of the responsive subjects. We found that the electromyographic (EMG) activity of proximal leg muscles was modulated over each cycle with a timing similar to that of normal locomotion. The frequency of kinematic and EMG oscillations in the legs typically differed from that of arm oscillations. The effect of hand-walking was direction specific since medio-lateral arm movements did not evoke appreciably leg air-stepping. Using externally imposed trunk movements and biomechanical modelling, we ruled out that the leg movements associated with hand-walking were mainly due to the mechanical transmission of trunk oscillations. EMG activity in hamstring muscles associated with hand-walking often continued when the leg movements were transiently blocked by the experimenter or following the termination of arm movements. The present results reinforce the idea that there exists a functional neural coupling between arm and legs.

Speed-dependent modulation of phase variations on a step-by-step basis and its impact on the consistency of interlimb coordination during quadrupedal locomotion in intact adult cats

It is well established that stance duration changes more than swing duration for a given change in cycle duration. Small variations in cycle duration are also observed at any given speed on a step-by-step basis. To evaluate the step-by-step effect of speed on phase variations, we measured the slopes of the linear regressions between the phases (i.e., stance, swing) and cycle duration during individual episodes at different treadmill speeds in five adult cats. We also determined the pattern of dominance, defined as the phase that varies most with cycle duration. We found a significant effect of speed on hindlimb phase variations, with significant differences observed between the slowest speed of 0.3 m/s compared with faster speeds. Moreover, although patterns of phase dominance were primarily stance/extensor dominated at the slowest speeds, as speed increased the patterns were increasingly categorized as covarying, whereby both stance/extensor and swing/flexor phases changed in approximately equal proportion with cycle duration. Speed significantly affected the relative duration of support periods as well as interlimb phasing between homolateral and diagonal pairs of limbs but not between homologous pairs of limbs. Speed also significantly affected the consistency of interlimb coordination on a step-by-step basis, being less consistent at the slowest speed of 0.3 m/s compared with faster speeds. We found a strong linear relationship between hindlimb phase variations and the consistency of interlimb coordination. Therefore, results show that phase variations on a step-by-step basis are modulated by speed, which appears to influence the consistency of interlimb coordination.

The how and why of arm swing during human walking

Humans walk bipedally, and thus, it is unclear why they swing their arms. In this paper, we will review the mechanisms and functions of arm swinging in human gait. First, we discuss the potential advantages of having swinging arms. Second, we go into the detail on the debate whether arm swing is arising actively or passively, where we will conclude that while a large part of arm swinging is mechanically passive, there is an active contribution of muscles (i.e. an activity that is not merely caused by stretch reflexes). Third, we describe the possible function of the active muscular contribution to arm swinging in normal gait, and discuss the possibility that a Central Pattern Generator (CPG) generates this activity. Fourth, we discuss examples from pathological cases, in which arm swinging is affected. Moreover, using the ideas presented, we suggest ways in which arm swing may be used as a therapeutic aid. We conclude that (1) arm swing should be seen as an integral part of human bipedal gait, arising mostly from passive movements, which are stabilized by active muscle control, which mostly originates from locomotor circuits in the central nervous system (2) arm swinging during normal bipedal gait most likely serves to reduce energy expenditure and (3) arm swinging may be of therapeutic value.

Amplification of interlimb reflexes evoked by stimulating the hand simultaneously with conditioning from the foot during locomotion

Background

Widespread interlimb reflexes evoked in leg muscles by cutaneous stimulation of the hand are phase-modulated and behaviorally relevant to produce functional changes in ankle trajectory during walking. These reflexes are complementary to the segmental responses evoked by stimulation at the ankle. Despite differences in the expression of reflex amplitude based upon site of nerve stimulation, there are some common features as well, suggesting the possibility of shared interneuronal pathways. Currently little is known about integration or shared reflex systems from interlimb cutaneous networks during human locomotion. Here we investigated convergent reflex effects following cutaneous stimulation of the hand and foot during arm and leg cycling (AL) by using spatial facilitation. Participants performed AL cycling and static activation of the target muscle knee extensor vastus lateralis (VL) in 3 different randomly ordered nerve stimulation conditions: 1) superficial radial nerve (SR; input from hand); 2) superficial peroneal nerve (SP; input from foot); and, 3) combined stimulation (SR + SP). Stimuli were applied around the onset of rhythmic EMG bursts in VL corresponding to the onset of the power or leg extension phase.

Results

During AL cycling, small inhibitory (~80 ms) and large facilitatory reflexes (~100 ~ 150 ms) were seen in VL. The amplitudes of the facilitatory responses with SR + SP stimulation were significantly larger than those for SP or SR stimulation alone. The facilitation was also significantly larger than the simple mathematical summation of amplitudes from SP and SR trials. This indicates extra facilitation beyond what would be accounted for by serial neuronal processing and was not observed during static activation.

Conclusions

We conclude that AL cycling activates shared interneurons in convergent reflex pathways from cutaneous inputs innervating the hand and leg. This enhanced activity has functional implications for corrective responses during locomotion and for translation to rehabilitation after neurotrauma.

Coordination between the fore- and hindlimbs is bidirectional, asymmetrically organized, and flexible during quadrupedal locomotion in the intact adult cat

Despite the obvious importance of inter-girdle coordination for quadrupedal locomotion in terrestrial mammals, its organization remains poorly understood. Here, we evaluated cycle and phase durations, as well as footfall patterns of four intact adult cats trained to walk on a transverse split-belt treadmill that could independently control fore- and hindlimb speed. When the hindlimbs walked at faster speeds than the forelimbs, an equal rhythm was always maintained between the fore- and hindlimbs, even at the highest fore-hindlimb speed ratio of 1:3 (0.4:1.2 m/s). The locomotor pattern adjusted through changes in both hindlimb stance and swing phase durations, whereas only the forelimb stance phase was affected. In such conditions, when fore- and hindlimb values were compared to those obtained at matched speeds during tied-belt walking (i.e. predicted values based on treadmill speed), hindlimb cycle, stance and swing durations were consistently longer than predicted. On the other hand, forelimb cycle and stance durations were shorter than predicted but only at the highest split-belt speed ratios. Forelimb swing durations were as predicted based on front-belt speed. The sequence of footfall pattern when hindlimb speed was faster was identical to tied-belt walking. In stark contrast, when the forelimbs walked at slightly faster speeds than the hindlimbs, the rhythm between the fore- and hindlimbs broke down. In such conditions, the locomotor pattern was adjusted through changes in stance and swing phase durations in both the fore- and hindlimbs. When the rhythm between the fore- and hindlimbs broke down, hindlimb cycle and phase durations were similar to predicted values, whereas forelimb values were shorter than predicted. Moreover, several additional sequences of footfall patterns were observed. Therefore, the results clearly demonstrate the existence of a bidirectional, asymmetric, and flexible control of inter-girdle coordination during quadrupedal locomotion in the intact adult cat.

Sensory regulation of quadrupedal locomotion: a top-down or bottom-up control system?

Propriospinal pathways are thought to be critical for quadrupedal coordination by coupling cervical and lumbar central pattern generators (CPGs). However, the mechanisms involved in relaying information between girdles remain largely unexplored. Using an in vitro spinal cord preparation in neonatal rats, Juvin and colleagues (Juvin et al. 2012) have recently shown sensory inputs from the hindlimbs have greater influence on forelimb CPGs than forelimb sensory inputs on hindlimb CPGs, in other words, a bottom-up control system. However, results from decerebrate cats suggest a top-down control system. It may be that both bottom-up and top-down control systems exist and that the dominance of one over the other is task or context dependent. As such, the role of sensory inputs in controlling quadrupedal coordination before and after injury requires further investigation.