Perception of gait patterns that deviate from normal and symmetric biped locomotion

Carrying Police Load Increases Gait Asymmetry in Ground Reaction Forces and Plantar Pressures Beneath Different Foot Regions in a Large Sample of Police Recruits

BACKGROUND

Although carrying external load has negative effects on gait biomechanics, little evidence has been provided regarding its impact on body asymmetry. The main purpose of the present study was to examine, whether standardized equipment produced greater gait asymmetries in ground reaction force and plantar pressure.

METHODS

For the purpose of this study, we recruited 845 police recruits (609 men and 236 women; 72.1% men and 27.9% women) measured in two conditions: (i) 'no load' and (ii) 'a 3.5 kg load'. Absolute values in ground reaction forces and plantar pressures beneath the different foot regions were assessed with pedobarographic platform (Zebris FDM). Asymmetry was calculated as (xright - xleft)/0.5 × (xright + xleft) × 100%, where 'x' represented a given parameter being calculated and a value closer to 0 denoted greater symmetry.

RESULTS

Significant differences in ground reaction forces and plantar pressures between the left and right foot were observed, when adding 'a 3.5 kg load'. Compared to the 'no load' condition, carrying 'a 3.5 kg load' significantly increased gait asymmetries for maximal ground reaction forces beneath the forefoot (ES = 0.29), midfoot (ES = 0.20) and hindfoot (ES = 0.19) regions of the foot. For maximal plantar pressures, only the asymmetry beneath the midfoot region of the foot significantly increased (ES = 0.19).

CONCLUSIONS

Findings of this study indicate that 'a 3.5 kg load' significantly increases ground reaction force and plantar pressure gait asymmetries beneath the forefoot and midfoot regions, compared to 'no load' condition. Due to higher loads, increases in kinetic gait asymmetries may have negative effects on future pain and discomfort in the foot area, possibly causing stress fractures and deviated gait biomechanics in police recruits.

The Effect of Knee Height Asymmetry on Gait Biomechanics

BACKGROUND

Though the primary goal for limb length discrepancy (LLD) management is to equalize the leg lengths, symmetry between corresponding long bones is usually not achieved, leading to knee height asymmetry (KHA). To date, there is minimal information on what effect KHA has on gait biomechanics and joint loading. Thus, the purpose of this study is to determine the impact of KHA on gait biomechanics.

METHODS

Seventeen subjects with KHA after limb equalizing surgery and 10 healthy controls were enrolled. Subjects participated in 3D gait analysis collected using self-selected speed. Lower extremity kinematics, kinetics, work generated/absorbed, and total work were calculated. Standing lower limb x-rays and scanograms were used to measure LLD and calculate the tibia-to-femur (TF) ratio for each limb. Two sample t tests were used to compare differences in standing LLD, TF ratio, and work between groups. Bivariate correlation using Pearson correlation coefficients was conducted between TF ratio and total mechanical work, as well as between knee height asymmetry indices and total work asymmetry (α=0.05).

RESULTS

Among participants, there were no differences between LLD; however, there were differences between TF ratio and knee height asymmetry. We found a nonsignificant relationship between TF ratio and total mechanical work for individual lower extremities. Therefore, the length of individual bones (TF ratio) relative to each other within the individual lower extremity was not associated with the amount of work produced. However, when a difference exists between sides (asymmetry, ie, TF ratio asymmetry), there were associated differences in work (work asymmetry) produced between sides (r=0.54, P =0.003). In other words, greater knee height asymmetry between limbs resulted in more asymmetrical mechanical work during walking.

CONCLUSIONS

These findings may have implications for the management of LLD. Asymmetrical total mechanical work could lead to atypical joint loading during gait. Surgeons may want to consider prioritizing achieving knee height symmetry as a postoperative goal when correcting limb length discrepancy.

LEVEL OF EVIDENCE

Level III, Case Control Study.

Learning hybrid locomotion skills-Learn to exploit residual actions and modulate model-based gait control

This work has developed a hybrid framework that combines machine learning and control approaches for legged robots to achieve new capabilities of balancing against external perturbations. The framework embeds a kernel which is a model-based, full parametric closed-loop and analytical controller as the gait pattern generator. On top of that, a neural network with symmetric partial data augmentation learns to automatically adjust the parameters for the gait kernel, and also generate compensatory actions for all joints, thus significantly augmenting the stability under unexpected perturbations. Seven Neural Network policies with different configurations were optimized to validate the effectiveness and the combined use of the modulation of the kernel parameters and the compensation for the arms and legs using residual actions. The results validated that modulating kernel parameters alongside the residual actions have improved the stability significantly. Furthermore, The performance of the proposed framework was evaluated across a set of challenging simulated scenarios, and demonstrated considerable improvements compared to the baseline in recovering from large external forces (up to 118%). Besides, regarding measurement noise and model inaccuracies, the robustness of the proposed framework has been assessed through simulations, which demonstrated the robustness in the presence of these uncertainties. Furthermore, the trained policies were validated across a set of unseen scenarios and showed the generalization to dynamic walking.

Gait asymmetry is associated with performance-based physical function among adults with lower-limb amputation

BACKGROUND

Adults with lower-limb amputation walk with an asymmetrical gait and exhibit poor functional outcomes, which may negatively impact quality-of-life.

OBJECTIVE

To evaluate associations between gait asymmetry and performance-based physical function among adults with lower-limb amputation.

METHODS

A cross-sectional study involving 38 adults with a unilateral transtibial (N = 24; 62.5 ± 10.5 years) or transfemoral amputation (N = 14; 59.9 ± 9.5 years) was conducted. Following gait analysis (capturing step length and stance time asymmetry at self-selected (SSWS) and fast walking speeds (FWS)), participants completed performance-based measures (i.e. Timed Up and Go (TUG), the 10-Meter Walk Test (10mwt), and the 6-Minute Walk Test (6MWT)).

RESULTS

Step length and stance time asymmetry (at SSWS and FWS) were significantly correlated with each performance-based measure (p < .001 to p = .035). Overall, models with gait measures obtained at SSWS explained 40.1%, 46.8% and 40.1% of the variance in TUG-time (p = .022), 10mwt-speed (p = .003) and 6MWT-distance (p = .010), respectively. Models with gait measures obtained at FWS explained 70.0%, 59.8% and 51.8% of the variance in TUG-time (p < .001), 10mwt-speed (p < .001), and 6MWT-distance (p < .001), respectively.

CONCLUSIONS

Increases in step length or stance time asymmetry are associated with increased TUG-time, slower 10mwt-speed, and reduced 6MWT-distance. Findings suggest gait asymmetry may be a factor in poor functional outcomes following lower-limb amputation.

Association Between Self-Perceived General Human-Likeness During Walking and Walking Speed in Stroke Patients: A Preliminary Study

The difference between the walking speeds of stroke patients and the general population may influence the self-perception of patients, who perceive their walk as lacking general human-likeness. Perception toward human-likeness during walking is defined here as the feeling that one can walk as intended, just like healthy people. Such negative subjective experiences may curb their social participation. However, the perception associated with walking speed in stroke patients is poorly understood. The main purpose of this study was to investigate the relationship between walking speed and perception toward general human-likeness during walking in stroke patients. Thirty-two post-stroke patients were enrolled in this cross-sectional study. Patients performed 10-m walk tests at comfortable and fast speeds and answered questions about their perceived human-like walking after completing the walk (“How much did you feel your walking resembled the human-likeness during walking of general people?”). We found a significant positive correlation between perception toward human-likeness during walking and walking speed at both comfortable and fast speeds. To the best of our knowledge, this report is the first to suggest that walking speed may correlate with self-perception. Our findings may help understand the underlying mechanism in patients perceiving less human-likeness during walking.

Real-time feedback control of split-belt ratio to induce targeted step length asymmetry

INTRODUCTION

Split-belt treadmill training has been used to assist with gait rehabilitation following stroke. This method modifies a patient's step length asymmetry by adjusting left and right tread speeds individually during training. However, current split-belt training approaches pay little attention to the individuality of patients by applying set tread speed ratios (e.g., 2:1 or 3:1). This generalization results in unpredictable step length adjustments between the legs. To customize the training, this study explores the capabilities of a live feedback system that modulates split-belt tread speeds based on real-time step length asymmetry.

MATERIALS AND METHODS

Fourteen healthy individuals participated in two 1.5-h gait training sessions scheduled 1 week apart. They were asked to walk on the Computer Assisted Rehabilitation Environment (CAREN) split-belt treadmill system with a boot on one foot to impose asymmetrical gait patterns. Each training session consisted of a 3-min baseline, 10-min baseline with boot, 10-min feedback with boot (6% asymmetry exaggeration in the first session and personalized in the second), 5-min post feedback with boot, and 3-min post feedback without boot. A proportional-integral (PI) controller was used to maintain a specified step-length asymmetry by changing the tread speed ratios during the 10-min feedback period. After the first session, a linear model between baseline asymmetry exaggeration and post-intervention asymmetry improvement was utilized to develop a relationship between target exaggeration and target post-intervention asymmetry. In the second session, this model predicted a necessary target asymmetry exaggeration to replace the original 6%. This prediction was intended to result in a highly symmetric post-intervention step length.

RESULTS AND DISCUSSION

Eleven out of 14 participants (78.6%) developed a successful relationship between asymmetry exaggeration and decreased asymmetry in the post-intervention period of the first session. Seven out of the 11 participants (63.6%) in this successful correlation group had second session post-intervention asymmetries of < 3.5%.

CONCLUSIONS

The use of a PI controller to modulate split-belt tread speeds demonstrated itself to be a viable method for individualizing split-belt treadmill training.

Walking abilities improvements are associated with pelvis and trunk kinematic adaptations in transfemoral amputees after rehabilitation

BACKGROUND

Rehabilitation can be proposed to transfemoral amputees to improve functional abilities and limit the risk of early degeneration of the musculoskeletal system partly due to altered kinematic behavior. The main aim of this study was to assess the impact of functional rehabilitation on clinical walking tests, gait symmetry and pelvis and trunk kinematics in transfemoral amputees during overground walking.

METHODS

Eleven transfemoral amputees followed a functional rehabilitation program with objectives aimed at improving walking abilities and gait symmetry. Clinical functional tests, symmetry between prosthetic and intact sides and trunk and pelvis motions were recorded before and after rehabilitation.

FINDINGS

Clinical walking tests were improved after rehabilitation (p < 0.05), and step width was reduced (p = 0.04). Regarding symmetry between the single stances on the prosthesis and intact sides, only a significant decrease in trunk frontal inclination asymmetry was noted after rehabilitation (p = 0.01). Pelvic frontal obliquity was significantly increased during prosthetic (p = 0.02) and intact single stances (p = 0.005).

INTERPRETATION

Our study showed a positive effect of rehabilitation on transfemoral amputees functional abilities. These improvements were associated with higher pelvic mobility in frontal plane and a more symmetrical redistribution of the frontal trunk sway around the vertical axis during gait. These results suggest the importance of a postural reeducation program for transfemoral amputees aimed at improving pelvic dynamic control while repositioning the trunk by postural corrections during gait.

A Meta-analysis of the Uncanny Valley's Independent and Dependent Variables

The uncanny valley (UV) effect is a negative affective reaction to human-looking artificial entities. It hinders comfortable, trust-based interactions with android robots and virtual characters. Despite extensive research, a consensus has not formed on its theoretical basis or methodologies. We conducted a meta-analysis to assess operationalizations of human likeness (independent variable) and the UV effect (dependent variable). Of 468 studies, 72 met the inclusion criteria. These studies employed 10 different stimulus creation techniques, 39 affect measures, and 14 indirect measures. Based on 247 effect sizes, a three-level meta-analysis model revealed the UV effect had a large effect size, Hedges’ g = 1.01 [0.80, 1.22]. A mixed-effects meta-regression model with creation technique as the moderator variable revealed face distortion produced the largest effect size, g = 1.46 [0.69, 2.24], followed by distinct entities, g = 1.20 [1.02, 1.38], realism render, g = 0.99 [0.62, 1.36], and morphing, g = 0.94 [0.64, 1.24]. Affective indices producing the largest effects were threatening, likable, aesthetics, familiarity , and eeriness , and indirect measures were dislike frequency, categorization reaction time, like frequency, avoidance , and viewing duration . This meta-analysis—the first on the UV effect—provides a methodological foundation and design principles for future research.

Minimal clinically important difference in walking velocity, gait profile score and two minute walk test for individuals with lower limb amputation

BACKGROUND

Individuals with lower limb amputation are routinely assessed with a variety outcome measures, however there is a lack of published data to indicate minimal clinically important differences (MCID) for many of these outcome measures. Three such important gait-specific outcome measures include walking velocity, gait profile score (GPS) and the two minute walk test (2MWT).

RESEARCH QUESTION

Determine the MCIDs for walking velocity, GPS and 2MWT for individuals with lower limb amputation.

METHODS

Walking velocity and GPS (n = 60), and 2MWT (n = 119) data for individuals with unilateral transfemoral or knee disarticulation were identified retrospectively from a database held at the study centre. An anchor-based method was used with Medicare functional classification level (MFCL) acting as the impairment-related criterion, and a least-squares linear regression approach was used to calculate the gradient required for a change between MFCL levels.

RESULTS

An increase of 0.21 m/s (95 % CI: 0.13,0.29) for walking velocity, a reduction of 1.7° (95 % CI: -2.449,-1.097) for GPS and an increase of 37.2 m (95 % CI: 28.8,45.5) for 2MWT were found to correspond to an increase in MFCL of one level. Walking velocity, GPS and 2MWT correlated with MFCL with R² values of 0.333, 0.322 and 0.398 respectively (p < 0.00001). The authors propose that 0.21 m/s for walking velocity, 1.7° for GPS and 37.2 m for 2MWT be used as MCID values for individuals with lower limb amputation.

SIGNIFICANCE

The results of this study can be used to help both researchers and clinicians to objectively evaluate if interventions for individuals with lower limb amputation are effective.

Asymmetric Gait Analysis Using a DTW Algorithm with Combined Gyroscope and Pressure Sensor

Walking is one of the most basic human activities. Various diseases may be caused by abnormal walking, and abnormal walking is mostly caused by disease. There are various characteristics of abnormal walking, but in general, it can be judged as asymmetric walking. Generally, spatiotemporal parameters can be used to determine asymmetric walking. The spatiotemporal parameter has the disadvantage that it does not consider the influence of the diversity of patterns and the walking speed. Therefore, in this paper, we propose a method to analyze asymmetric walking using Dynamic Time Warping (DTW) distance, a time series analysis method. The DTW distance was obtained by combining gyroscope data and pressure data. The experiment was carried out by performing symmetrical walking and asymmetrical walking, and asymmetric walking was performed as a simulation of hemiplegic walking by fixing one ankle using an auxiliary device. The proposed method was compared with the existing asymmetric gait analysis method. As a result of the experiment, a p-value lower than 0.05 was obtained, which proved that there was a statistically significant difference.

Effect Of Transtibial Prosthesis Mass On Gait Asymmetries

BACKGROUND

Individuals with transtibial amputation (TTA) typically walk with an asymmetrical gait pattern, which may predispose them to secondary complications and increase risk of fall. Gait asymmetry may be influenced by prosthesis mass.

OBJECTIVES

To explore the effects of prosthesis mass on temporal and limb loading asymmetry in people with TTA following seven days of acclimation and community use.

METHODOLOGY

Eight individuals with transtibial amputation participated. A counterbalanced repeated measures study, involving three sessions (each one week apart) was conducted, during which three load conditions were examined: no load, light load and heavy load. The light load and heavy load conditions were achieved by adding 30% and 50% of the mass difference between legs, at a proximal location on the prosthesis. Kinematic and ground reaction force data was captured while walking one week after the added mass. Symmetry indices between the prosthetic and intact side were computed for temporal (Stance and Swing time) and limb loading measures (vertical ground reaction force Peak and Impulse).

FINDINGS

Following seven days of acclimation, no significant differences were observed between the three mass conditions (no load, light load and heavy load) for temporal (Stance time: p=0.61; Swing time: p=0.13) and limb loading asymmetry (vertical ground reaction force Peak: p=0.95; vertical ground reaction force Impulse: p=0.55).

CONCLUSIONS

Prosthesis mass increase at a proximal location did not increase temporal and limb loading asymmetry during walking in individuals with TTA. Hence, mass increase subsequent to replacing proximally located prosthesis components may not increase gait asymmetry, thereby allowing more flexibility to the clinician for component selection.

Novel passive ankle-foot prosthesis mimics able-bodied ankle angles and ground reaction forces

BACKGROUND

During gait, the human ankle both bends with ease and provides push-off forces that facilitate forward motion. The ankle is crucial for support, stabilization, and adapting to different slopes and terrains. Individuals with lower limb amputation require an ankle-foot prosthesis for basic mobility.

METHODS

Inspired by the role of the ankle-foot in an able-bodied gait, the 3D printed Compliant and Articulating Prosthetic Ankle (CAPA) foot was designed. It consists of four articulating components connected by torsion springs and produces forces that are dependent on the ankle angle. Using the Computer Assisted Rehabilitation Environment, able-bodied individuals walked wearing a prosthetic simulator with the Solid Ankle Cushioned Heel foot, Renegade® AT, and multiple versions of the CAPA. These versions test compliant vs. stiff, small vs. large rocker radius, and pretension vs. none. We hypothesized that the CAPA would have larger ankle range of motion, push-off forces, and braking forces.

FINDINGS

Compared to existing prostheses, the novel prosthesis exhibits greater and significantly different ankle range of motion and sagittal plane ground reaction forces than existing prostheses during gait. Nine out of ten individuals prefer the novel prosthesis to the existing prostheses, and there is a statistically significant difference in difficulty level ratings.

INTERPRETATION

By providing a personalizable and passive alternative to existing designs, the CAPA could improve the quality of life for the growing number of individuals living with limb loss in the United States and around the world.

Human Gait Analysis Metric for Gait Retraining

The combined gait asymmetry metric (CGAM) provides a method to synthesize human gait motion. The metric is weighted to balance each parameter's effect by normalizing the data so all parameters are more equally weighted. It is designed to combine spatial, temporal, kinematic, and kinetic gait parameter asymmetries. It can also combine subsets of the different gait parameters to provide a more thorough analysis. The single number quantifying gait could assist robotic rehabilitation methods to optimize the resulting gait patterns. CGAM will help define quantitative thresholds for achievable balanced overall gait asymmetry. The study presented here compares the combined gait parameters with clinical measures such as timed up and go (TUG), six-minute walk test (6MWT), and gait velocity. The comparisons are made on gait data collected on individuals with stroke before and after twelve sessions of rehabilitation. Step length, step time, and swing time showed a strong correlation to CGAM, but the double limb support asymmetry has nearly no correlation with CGAM and ground reaction force asymmetry has a weak correlation. The CGAM scores were moderately correlated with TUG and strongly correlated to 6MWT and gait velocity.

A Spinal Mechanism Related to Left-Right Symmetry Reduces Cutaneous Reflex Modulation Independently of Speed During Split-Belt Locomotion

Task- and phase-dependent reflex modulation during locomotion is well established, but we do not know the signals driving this modulation. To determine whether signals related to left-right symmetry of the locomotor pattern modulate cutaneous reflexes, we stimulated the superficial peroneal nerve in five intact female cats and in four spinal-transected cats (spinal cats, two males and two females) during split-belt locomotion at different left-right speeds. We compared cutaneous reflexes evoked in three ipsilateral and two contralateral hindlimb muscles during split-belt locomotion with those evoked during tied-belt (equal left-right speeds) locomotion at matched speeds of the slow and fast limbs. Our results showed similar phase-dependent modulation of cutaneous reflexes during tied-belt and split-belt locomotion in intact and spinal cats. During tied-belt locomotion in intact cats, an increase in speed significantly increased reflex modulation from minimum to maximum values, whereas in spinal cats, we observed a significant decrease. However, in all muscles of intact and spinal cats, split-belt locomotion significantly reduced reflex modulation compared with tied-belt locomotion independently of which limb was stepping on the slow or fast belt. Additionally, reflex modulation correlated more with spatial left-right symmetry, as opposed to a temporal one, in intact and spinal cats. Our results indicate that signals related to left-right symmetry reduce cutaneous reflex modulation independently of speed via a spinal mechanism. We propose that asymmetric sensory feedback from the left and right legs alters the state of the spinal network, thereby reducing cutaneous reflexes to prevent inputs from destabilizing a potentially unstable pattern.SIGNIFICANCE STATEMENT When we contact an obstacle during walking, receptors in the skin send signals to the CNS to alter the trajectory of the leg to maintain balance. This response, or reflex, is different when the leg is in the air and when it is contacting the ground. The reflex also differs when we walk at different speeds. Here, we investigated this reflex when the left and right legs were walking at different speeds on a split-belt treadmill in cats. We show that the reflex is smaller during split-belt locomotion compared with when both legs are walking at equal speeds. We propose that the spinal locomotor network controlling walking reduces the reflex response to optimize balance when gait is unstable.

Reference values for gait temporal and loading symmetry of lower-limb amputees can help in refocusing rehabilitation targets

Background

The literature suggests that optimal levels of gait symmetry might exist for lower-limb amputees. Not only these optimal values are unknown, but we also don’t know typical symmetry ratios or which measures of symmetry are essential. Focusing on the symmetries of stance, step, first peak and impulse of the ground reaction force, the aim of this work was to answer to three methodological and three clinical questions. The methodological questions wanted to establish a minimum set of symmetry indexes to study and if there are limitations in their calculations. The clinical questions wanted to establish if typical levels of temporal and loading symmetry exist, and change with the level of amputation and prosthetic components.

Methods

Sixty traumatic, K3-K4 amputees were involved in the study: 12 transfemoral mechanical knee users (TFM), 25 C-leg knee users (TFC), and 23 transtibial amputees (TT). Ninety-two percent used the Ossur Variflex foot. Ten healthy subjects were also included. Ground reaction force from both feet were collected with the Novel Pedar-X. Symmetry indexes were calculated and statistically compared with regression analyses and non-parametric analysis of variance among subjects.

Results

Stance symmetry can be reported instead of step, but it cannot substitute impulse and first peak symmetry. The first peak cannot always be detected on all amputees. Statistically significant differences exist for stance symmetry among all groups, for impulse symmetry between TFM and TFC/TT, for first peak symmetry between transfemoral amputees altogether and TT. Regarding impulse symmetry, 25% of TFC and 43% of TT had a higher impulse on the prosthetic side. Regarding first peak symmetry, 59% of TF and 30% of TT loaded more the prosthetic side.

Conclusions

Typical levels of symmetry for stance, impulse and first peak change with the level of amputation and componentry. Indications exist that C-leg and energy-storage-and-return feet can improve symmetry. Results are suggestive of two mechanisms related to sound side knee osteoarthritis: increased impulse for TF and increased first peak for TT. These results can be useful in clinics to set rehabilitation targets, understand the advancements of a patient during gait retraining, compare and chose components and possibly rehabilitation programs.

Incidence of knee height asymmetry in a paediatric population of corrected leg length discrepancy: a retrospective chart review study

PURPOSE

The purpose of the study is to provide a methodology to quantify knee height asymmetry (KHA) and to establish the incidence of knee height asymmetry in a patient population visiting the limb length discrepancy clinic in a paediatric-orthopaedic hospital centre.

METHOD

A retrospective chart review was performed on all patients who attended the limb length discrepancy clinic and underwent corrective surgery at the Shriners Hospital for Children-Canada from December 2009 to December 2015. Full-standing anteroposterior radiographs were used to measure pre- and post-surgery limb length discrepancy and knee height asymmetry for 52 individuals included in the study.

RESULTS

Sixty-seven percent of the studied population had a KHA of 20 mm or less, 25% had a KHA between 20 and 40 mm, and 8% had a KHA of over 40 mm. The average KHA preoperatively for all 52 individuals was 17 ± 14 mm (range 0-59 mm), which represents roughly 2.5% of total limb length. There was a 3-mm non-significant reduction in KHA size between pre-and post-operative states (p = 0.22).

CONCLUSION

The current study provides a method to quantify knee height asymmetry. Using this method, it was shown that knee height asymmetry is frequent in youth with limb length discrepancy in both pre- and post-corrective surgery states. The relatively high incidence of knee height asymmetry highlights the importance to investigate the impact of knee height asymmetry in youth living with a limb length discrepancy.