Step In Place Research Articles

Asymmetry measures for quantification of mechanisms contributing to dynamic stability during stepping-in-place gait.

The goal of this study is to introduce and to motivate the use of new quantitative methods to improve our understanding of mechanisms that contribute to the control of dynamic balance during gait. Dynamic balance refers to the ability to maintain a continuous, oscillating center-of-mass (CoM) motion of the body during gait even though the CoM frequently moves outside of the base of support. We focus on dynamic balance control in the frontal plane or medial-lateral (ML) direction because it is known that active, neurally-mediated control mechanisms are necessary to maintain ML stability. Mechanisms that regulate foot placement on each step and that generate corrective ankle torque during the stance phase of gait are both known to contribute to the generation of corrective actions that contribute to ML stability. Less appreciated is the potential role played by adjustments in step timing when the duration of the stance and/or swing phases of gait can be shortened or lengthened to allow torque due to gravity to act on the body CoM over a shorter or longer time to generate corrective actions. We introduce and define four asymmetry measures that provide normalized indications of the contribution of these different mechanisms to gait stability. These measures are 'step width asymmetry', 'ankle torque asymmetry', 'stance duration asymmetry', and 'swing duration asymmetry'. Asymmetry values are calculated by comparing corresponding biomechanical or temporal gait parameters from adjacent steps. A time of occurrence is assigned to each asymmetry value. An indication that a mechanism is contributing to ML control is obtained by comparing asymmetry values to the ML body motion (CoM angular position and velocity) at the time points associated with the asymmetry measures. Example results are demonstrated with measures obtained during a stepping-in-place (SiP) gait performed on a stance surface that either remained fixed and level or was pseudorandomly tilted to disturb balance in the ML direction. We also demonstrate that the variability of asymmetry measures obtained from 40 individuals during unperturbed, self-paced SiP were highly correlated with corresponding coefficient of variation measures that have previously been shown to be associated with poor balance and fall risk.

Gait Parameters Measured from Wearable Sensors Reliably Detect Freezing of Gait in a Stepping in Place Task.

Freezing of gait (FOG), a debilitating symptom of Parkinson’s disease (PD), can be safely studied using the stepping in place (SIP) task. However, clinical, visual identification of FOG during SIP is subjective and time consuming, and automatic FOG detection during SIP currently requires measuring the center of pressure on dual force plates. This study examines whether FOG elicited during SIP in 10 individuals with PD could be reliably detected using kinematic data measured from wearable inertial measurement unit sensors (IMUs). A general, logistic regression model (area under the curve = 0.81) determined that three gait parameters together were overall the most robust predictors of FOG during SIP: arrhythmicity, swing time coefficient of variation, and swing angular range. Participant-specific models revealed varying sets of gait parameters that best predicted FOG for each participant, highlighting variable FOG behaviors, and demonstrated equal or better performance for 6 out of the 10 participants, suggesting the opportunity for model personalization. The results of this study demonstrated that gait parameters measured from wearable IMUs reliably detected FOG during SIP, and the general and participant-specific gait parameters allude to variable FOG behaviors that could inform more personalized approaches for treatment of FOG and gait impairment in PD.

User-defined walking-in-place gestures for VR locomotion

Locomotion is one of the fundamental interactions in VR. As a relatively easy and simple method to implement VR locomotion, walking-in-place (WIP) techniques have been actively developed, which have shown advantages in terms of spatial constraints and immersion compared to real walking or controller-based interaction. However, existing WIP gestures have been largely adapted or designed from the perspective of developers, not the users, which may result in not only higher cognitive load to learn and memorize, but also worse presence and increased sensory conflict in VR. Therefore, this study aims to elicit and evaluate WIP gestures for different walking directions (forward, sideways, and backward) from users so that a complete user-defined WIP gesture set for VR locomotion can be generated. Two sequential user studies were conducted. In Experiment 1, 20 participants experienced the movement while wearing the VR headset and elicited the gesture for each of 8 walking directions. The grouping analysis revealed that Turn body + Stepping-in-place (SIP) and Step one foot + SIP/Rock/Stay were promising WIP gesture sets for VR locomotion. In the follow-up experiment (Experiment 2), 21 new participants experienced and compared the generated gesture sets and existing ones. The results showed that SIP performed the best for forward walking, while Step one foot + SIP/Rock/Stay were promising for other walking directions, which depended on application scenarios and the tradeoff between efficiency and naturalness. The generated WIP gesture sets from users can be used in VR applications to provide a better user experience and greater movement options in VR locomotion.

Gait variability is linked to the atrophy of the Nucleus Basalis of Meynert and is resistant to STN DBS in Parkinson's disease

Parkinson's disease (PD) is a systemic brain disorder where the cortical cholinergic network begins to degenerate early in the disease process. Readily accessible, quantitative, and specific behavioral markers of the cortical cholinergic network are lacking. Although degeneration of the dopaminergic network may be responsible for deficits in cardinal motor signs, the control of gait is a complex process and control of higher-order aspects of gait, such as gait variability, may be influenced by cognitive processes attributed to cholinergic networks. We investigated whether swing time variability, a metric of gait variability that is independent from gait speed, was a quantitative behavioral marker of cortical cholinergic network integrity in PD.Twenty-two individuals with PD and subthalamic nucleus (STN) deep brain stimulation (PD-DBS cohort) and twenty-nine age-matched controls performed a validated stepping-in-place (SIP) task to assess swing time variability off all therapy. The PD-DBS cohort underwent structural MRI scans to measure gray matter volume of the Nucleus Basalis of Meynert (NBM), the key node in the cortical cholinergic network. In order to determine the role of the dopaminergic system on swing time variability, it was measured ON and OFF STN DBS in the PD-DBS cohort, and on and off dopaminergic medication in a second PD cohort of thirty-two individuals (PD-med). A subset of eleven individuals in the PD-DBS cohort completed the SIP task again off all therapy after three years of continuous DBS to assess progression of gait impairment.Swing time variability was significantly greater (i.e., worse) in PD compared to controls and greater swing time variability was related to greater atrophy of the NBM, as was gait speed. STN DBS significantly improved cardinal motor signs and gait speed but did not improve swing time variability, which was replicated in the second cohort using dopaminergic medication. Swing time variability continued to worsen in PD, off therapy, after three years of continuous STN DBS, and NBM atrophy showed a trend for predicting the degree of increase. In contrast, cardinal motor signs did not progress. These results demonstrate that swing time variability is a reliable marker of cortical cholinergic health, and support a framework in which higher-order aspects of gait control in PD are reliant on the cortical cholinergic system, in contrast to other motor aspects of PD that rely on the dopaminergic network.

Functional electrical stimulation of permanently denervated muscles, updated 2020

Spinal cord injury produces muscle wasting, which is especially severe after the complete and permanent damage of lower motor neurons that occurs in complete Cauda Equina Syndrome. Even in this worst-case scenario, we have shown that permanently denervated Quadriceps muscle can be rescued by surface Functional Electrical Stimulation and a purpose designed home-based rehabilitation regime. Here, our aim is to show that the effects are extended to both antagonist muscles and the skin of the thighs. Before and after 2 years of electrical stimulation, mass and structure of Quadriceps and Hamstrings muscles were quantitated by force measurements. Muscle gross cross section were evaluated using color computed tomography, muscle and skin biopsies by quantitative histology and immunohistochemistry. The treatment produced: a) an increase in cross-sectional area of stimulated muscles; b) an increase in muscle fiber mean diameter; c) improvements in ultrastructural organization; and d) increased force output during electrical stimulation. The recovery of Quadriceps muscle force was sufficient to allow 25% of the compliant subjects to perform stand-up and step-in place trainings. Improvements are extended to hamstring muscles and skin. Indeed, the cushioning effect provided by recovered tissues is a major clinical benefit. It is our hope that, with or without our advice, trials may start soon in Europe and Russia to provide persons-in-need the help they deserve.

Effects of rhythmic auditory cueing on stepping in place in patients with Parkinson's disease.

Background:Stepping in place (SIP) is a useful locomotor training intervention. The purpose of this study was to investigate the effects of single auditory-cued SIP training on cortical excitability, rhythmic movements and walking ability in patients with Parkinson's disease(PD).Methods:Cross-over randomized control trial. Each participant completed two interventions with at least one-week washout period in between: (1) SIP with concurrent auditory cues (AC condition) and (2) SIP without auditory cues (NC condition).Results:In the primary outcome, the cortical silent period (CSP) duration increased (P = .005), whereas short intracortical inhibition (SICI) decreased after training (P = .001). Freezers demonstrated enhanced inhibition in the resting motor threshold and CSP duration. SICI and intracortical facilitation were modulated in both groups under the AC condition. In the secondary outcomes, the stepping variability decreased significantly (AC: P = .033; NC: P = .009), whereas walking cadence increased after training (AC: P = .019; NC: P = .0023).Conclusions:Auditory-cued SIP training improved the lower-limb movement variability and modulated the cortical excitability in patients with PD. Freezers may benefit more from this training than nonfreezers.

Interest of the task of “Stepping in place” in the assessment of freezing in Parkinson's disease patients

Freezing of gait (FOG) in Parkinson's disease (PD) is challenging to measure. Repetitive stepping in place (SIP) task on force plates has been proposed by Nantel et al. in 2011 for identifying freezing episodes (FEs) in PD patients. These authors have correlated this task with the validated FOG questionnaire (FOG-Q). The inability to maintain a walking rhythm could be alleviated by external cues involving a sensorimotor network underlying the processing of rhythm (Dalla Bella et al., 2014) Twenty-four PD patients have been included: 8 without freezing, 8 with severe freezing and 8 mild “freezers”. PD subjects were assessed using the MDS-UPDRS, MoCA, FAST, MiniBest test, questionnaires, and were submitted to the BAASTA battery, which consists of a series of perceptual timing and sensory timing tasks. Single wireless inertial sensors were placed on the patient's lower limbs. A computerized algorithm providing automatic detection of FEs during SIP, Timed Up and Go test and 20 m walk has been used. Preliminary results show that there is some discrepancy between patients self-assessment, SIP and walking task measurements. The occurrence of freezing episodes is highly variable in mild freezers and depends on the emotional context and the repetition of the tasks. This could be explained by the fact that the timing of our assessment has been performed in less severe off state than in Nantel's study(12 hours off Dopa) and which is closer to the patients’ daily life. SIP is of limited interest in the assessment of freezing in patients with partial “on state”. Analysis of correlations with neurological status, kinematics, perceptual and motor timing tasks will aid in clarifying the interest of this new task in the assessment of freezing in PD patients.

A new quantitative method for evaluating freezing of gait and dual-attention task deficits in Parkinson's disease.

People with Parkinson's disease (PD) can exhibit disabling gait symptoms such as freezing of gait especially when distracted by a secondary task. Quantitative measurement method of this type of cognitive-motor abnormality, however, remains poorly developed. Here we examined whether stepping-in-place (SIP) with a concurrent mental task (e.g., subtraction) can be used as a simple method for evaluating cognitive-motor deficits in PD. We used a 4th generation iPod Touch sensor system to capture hip flexion data and obtain step height (SH) measurements (z axis). The accuracy of the method was compared to and validated by kinematic video analysis software. We found a general trend of reduced SH for PD subjects relative to controls under all conditions. However, the SH of PD freezers was significantly worse than PD non-freezers and controls during concurrent serial 7 subtraction and SIP tasking. During serial 7 subtraction, SH was significantly associated with whether or not a PD patient was a self-reported freezer even when controlling for disease severity. Given that this SIP-based dual-task paradigm is not limited by space requirements and can be quantified using a mobile tracking device that delivers specifically designed auditory task instructions, the method reported here may be used to standardize clinical assessment of cognitive-motor deficits under a variety of dual-task conditions in PD.

The effect of medication and the role of postural instability in different components of freezing of gait (FOG)

Freezing of gait (FOG) is associated with gait asymmetry and arrhythmicity, cognitive impairment in Parkinson's disease (PD). However, the role of postural instability (PI) in and the effect of dopaminergic medication (meds) on FOG are unclear. We investigated the effect of meds on FOG using a validated metric, Stepping in Place (SIP) and the relationship between PI and FOG. MethodsWe assessed static posturography (off meds), SIP, UPDRS-III (off/on meds) and the FOG-questionnaire (FOG-Q) in 15 freezers/15 non-freezers and 14 healthy controls. ResultsUPDRS-III, rigidity, tremor (P < 0.01) and axial subscores (P < 0.05) improved with meds in freezers. Only UPDRS-III and tremor improved in non-freezers (P < 0.01). Meds improved freezing episode (FE) frequency, duration and stride duration in freezers (P < 0.01). Over 73% of freezers did not freeze on meds, although one freezer had more and longer duration FEs. Meds did not improve SIP cycle asymmetry and arrhythmicity, which remained greater in freezers compared to other groups on and off meds (P < 0.01, P < 0.05 respectively). Center of pressure (CoP) mediolateral displacement and velocity (VCoP) in both directions were larger in freezers (P < 0.05). FOG-Q was correlated with CoP anteroposterior displacement and mediolateral VCoP (R = 0.42; R = 0.40, P < 0.05).The improvement of FOG frequency and duration but not of gait asymmetry and arrhythmicity on meds suggests that both dopaminergic and non-dopaminergic networks contribute to FOG. The correlations between postural instability and FOG severity and SIP asymmetry on meds, suggest that as the disease progresses, postural instability interferes with gait symmetry and lead to on meds FOG and falls.

Deficits in visuospatial processing contribute to quantitative measures of freezing of gait in Parkinson’s disease

Objectives: The aim of this study was to investigate whether an objective measure of freezing of gait (FOG) using a validated alternating stepping in place (SIP) task, is related to executive and/or visuospatial cognitive impairment in Parkinson’s disease (PD). Methods: We studied prospectively 30 PD subjects with the Unified Parkinson’s Disease Rating Scale (UPDRS) III, the FOGq, Trail Making Test Part B (TMTB), Wisconsin Card Sorting, Initiation/Perseveration, Matrix Reasoning (MR) and Block Design (BD). PD subjects performed three, 100s trials of alternative SIP while standing on two force platforms to assess the number and duration of freezing episodes (FE), SIP rhythmicity and symmetry. Results: Freezers had larger cycle asymmetry and arrhythmicity than non-freezers (P<0.05). Performance on BD and MR tests differentiated freezers from non-freezers (P<0.04; P=0.001, respectively). BD performance negatively correlated with the FOGq total (P<0.05), the number and duration of FE (P<0.01), SIP arrhythmicity and asymmetry (P=0.01, P<0.05). MR performance negatively correlated with all FOGq #3 and total as well as SIP FE metrics (P⩽0.01), except for SIP asymmetry. Conclusion: Deficits in visuospatial perception and reasoning not in executive function differentiated freezers from non-freezers. Deficits in visuospatial processing negatively correlated with all SIP freeze metrics, whereas deficits in executive function were only correlated with SIP arrhythmicity, the FOGq total and the duration of freezing episodes. These results suggest that deficits in visuospatial processing to perform a motor task contribute to FOG and that different cognitive deficits may contribute to different aspects of freezing in PD. This is the first study to our knowledge that has compared metrics of freezing to cognitive tasks in the visuospatial and visual reasoning domains.

Repetitive stepping in place identifies and measures freezing episodes in subjects with Parkinson's disease

Freezing of gait (FOG) in Parkinson's disease (PD) is challenging to measure. We asked whether a repetitive stepping in place (SIP) task on force plates could identify freezing episodes (FEs) in PD subjects, self-classified as “freezers”, using the validated FOG questionnaire (FOG-Q) and whether a computerized algorithm could provide automatic detection of FEs during SIP. Thirty PD subjects and nine age-matched controls completed the SIP task. PD subjects were assessed using the Unified Parkinson's Disease Rating motor Scale (UPDRS-III) and the FOG-Q. The identification of “freezers” using the SIP task correlated with the FOG-Q (r=0.80, P<0.001). The specificity and sensitivity of identifying freezers using the SIP task reached 93% and 87%. The number and duration of FEs detected by the algorithm correlated with visual inspection (r=0.97, r=0.998, P<0.001). Freezers had larger SIP asymmetry compared to controls (P=0.02) and non-freezers (P=0.03) as well as larger arhythmicity (P=0.003 and P<0.001, respectively). UPDRS subscores were higher in freezers compared to non-freezers (P<0.05). These results suggest that the SIP task is a useful tool to detect freezing in PD and is correlated with FOG-Q. SIP cycle asymmetry and stride time variability were worse in freezers, similar to that shown in FOG studies. Detection of the number and duration of FEs using a computerized algorithm correlated with independent visual inspection of records.

Kinematic and Kinetic Analysis of a Stepping-in-Place Task in Below-Knee Amputee Children Compared to Able-Bodied Children

It has been demonstrated that below-knee amputee (BKA) subjects use specific compensation strategies to overcome their physical limitations. Biomechanical studies emphasize that the motor strategies adopted by BKA adults differ between their amputated limb and their nonamputated limb and from those employed by able-bodied (AB) subjects. The purpose of this investigation was to compare the motor solutions used by control AB and BKA children during a stepping-in-place (SIP) task and to assess how they regulate the coordination of their nonamputated and amputated limbs during this task. Eight BKA children and eight AB children paired for gender, age, weight and height participated in our study. One-way analysis of variances (ANOVAs) were performed on peaks of angular excursion, moment, and power at the hip, knee, and ankle to compare motor strategies between the BKA and AB groups. The main results of our experiment showed that even if BKA and AB children did the task with almost the same kinematics, the kinetic data revealed completely different mechanisms of the two groups to achieve the SIP task, and BKA children had a symmetrical interlimb strategy. SIP, a simple task compared to gait at the level of neuro-musculoskeletal demands, could thus offer a transition task to physical therapists for below-knee recently-amputated children.

Differences in the coordination of agonist and antagonist muscle groups in below-knee amputee and able-bodied children during dynamic exercise

A lack of co-contraction may predispose to knee instability or laxity, resulting in additional shear stress on the internal structures of the knee, especially in below-knee amputee (BKA) subjects. The purposes of this study were: (1) to provide information on how BKA children regulate agonist and antagonist muscle coordination, and (2) to quantify the level of knee co-contraction in able-bodied (AB) and BKA children during the stepping-in-place (SIP) task. Fourteen children (7 BKA vs. 7 AB), paired for age, weight and height, participated in this study. One-way ANOVA with Newman–Keuls post hoc tests ( p < 0.05) were used to compare peak power, the co-contraction index, and the resultant agonist and antagonist moments during different phases of SIP. Statistical analysis revealed that BKA children perform the task with similar kinematics than AB children while they generated less co-contraction in both their non-amputated limb and amputated limb, notably because the two groups of children used different agonist and antagonist muscles during the same periods of the SIP. This lack of co-contraction may reduce knee stability and may stress the internal structures of the knee in both the NAL and AL, and may lead to the development of premature knee osteoarthritis.

The Step in Place Test

0718 PURPOSE: This study aimed to evaluate four candidate clinical tests of stepping speed against laboratory measures of stepping speed before and after an exercise intervention. METHODS: Healthy older males (n = 20) and females (n = 28) aged 65–82 yrs were randomized into one of two 12-week, three day/week exercise programs: 34 subjects performed high-velocity resistance training (HVRT) targeting muscular strength and power for five leg exercises, and 14 subjects performed whole-body flexibility and upper-body resistance training (FUBT). Muscular strength (onerepetition maximum), muscular power (tested on the resistance training machines) and rapid stepping tests were performed pre- and post-intervention. Three laboratory stepping tests (LAB) were performed – two were tests of volitional stepping and one was a test of compensatory stepping due to lateral destabilization. Four clinically oriented stepping tests were also evaluated to determine their utility as proxy tests for stepping speed: the Step in Place (SIP) Test, Repeated Step Up Test, Side Step Test and Four Square Step Test (FSST)). These tests, except for FSST, were modified from versions utilized in previous literature. The LAB measurements were made with sophisticated laboratory equipment including instrumented platforms and computers, while the clinical test outcomes (in units of time) were measured with a stopwatch. Analyses of variance were used to determine improvements in stepping performance with exercise, and regression analyses were used to determine the factors involved in the improvements. RESULTS: As reported previously, most LAB parameters (reaction time, amplitude and duration of anticipatory postural adjustments, stepping speed) improved regardless of exercise group for volitional and compensatory stepping. Subjects also improved on the clinical stepping tests. Only SIP was well related to the improvements in performance on LAB tests; improvements on LAB performance explained an additional 28.7% of the variance in SIP improvements following exercise training in addition to the other variables (which were pre-intervention SIP time, exercise group assignment, and the improvements in strength and power variables; full model R2 = 72.9%, p = 0.000). Those who were the slowest prior to the intervention improved the most. CONCLUSIONS: SIP has good potential as a proxy test of stepping speed in lieu of laboratory stepping tests for older adults. Since speed of movement is an important risk factor for falling, SIP may be useful as a proxy test of stepping speed in fall risk assessments of older adults.