Overground Locomotion Research Articles

Remote Gait Analysis Using Ultra-Wideband Radar Technology Based on Joint Range-Doppler-Time Representation.

In recent years, radar technology has been extensively utilized in contactless human behavior monitoring systems. The unique capabilities of ultra-wideband (UWB) radars compared to conventional radar technologies, due to time-of-flight measurements, present new untapped opportunities for in-depth monitoring of human movement during overground locomotion. This study aims to investigate the deployability of UWB radars in accurately capturing the gait patterns of healthy individuals with no known walking impairments. A novel algorithm was developed that can extract ten clinical spatiotemporal gait features using the Doppler information captured from three monostatic UWB radar sensors during a 6-meter walking task. Key gait events are detected from lower-extremity movements based on the joint range-Doppler-time representation of recorded radar data. The estimated gait parameters were validated against a gold-standard optical motion tracking system using 12 healthy volunteers. On average, nine gait parameters can be consistently estimated with 90-98% accuracy, while capturing 94.5% of participants' gait variability and 90.8% of inter-limb symmetry. Correlation and Bland-Altman analysis revealed a strong correlation between radar-based parameters and the ground-truth values, with average discrepancies consistently close to 0. Results prove that radar sensing can provide accurate biomarkers to supplement clinical human gait analysis, with quality similar to gold standard assessment. Radars can potentially allow a transition from expensive and cumbersome lab-based gait analysis tools toward a completely unobtrusive and affordable solution for in-home deployment, enabling continuous long-term monitoring of individuals for research and healthcare applications.

ROLE OF FORELIMB MORPHOLOGY IN MUSCLE SENSORIMOTOR FUNCTIONS DURING LOCOMOTION IN THE CAT.

Previous studies established strong links between morphological characteristics of mammalian hindlimb muscles and their sensorimotor functions during locomotion. Less is known about the role of forelimb morphology in motor outputs and generation of sensory signals. Here, we measured morphological characteristics of 46 forelimb muscles from 6 cats. These characteristics included muscle attachments, physiological cross-sectional area (PCSA), fascicle length, etc. We also recorded full-body mechanics and EMG activity of forelimb muscles during level overground and treadmill locomotion in 7 and 16 adult cats of either sex, respectively. We computed forelimb muscle forces along with force- and length-dependent sensory signals mapped onto corresponding cervical spinal segments. We found that patterns of computed muscle forces and afferent activities were strongly affected by the muscle's moment arm, PCSA, and fascicle length. Morphology of the shoulder muscles suggests distinct roles of the forelimbs in lateral force production and movements. Patterns of length-dependent sensory activity of muscles with long fibers (brachioradialis, extensor carpi radialis) closely matched patterns of overall forelimb length, whereas the activity pattern of biceps brachii matched forelimb orientation. We conclude that cat forelimb muscle morphology contributes substantially to locomotor function, particularly to control lateral stability and turning, rather than propulsion.

Air-stepping in the neonatal mouse: a powerful tool for analyzing early stages of rhythmic limb movement development.

There is a lack of experimental methods in genetically tractable mouse models to analyze the developmental period at which newborns mature weight-bearing locomotion. To overcome this deficit, we introduce methods to study l-3,4-dihydroxyphenylalanine (l-DOPA)-induced air-stepping in mice at postnatal day (P)7 and P10. Air-stepping is a stereotypic rhythmic behavior that resembles mouse walking overground locomotion but without constraints imposed by weight bearing, postural adjustments, or sensory feedback. We propose that air-stepping represents the functional organization of early spinal circuits coordinating limb movements. After subcutaneous injection of l-DOPA (0.5 mg/g), we recorded air-stepping movements in all four limbs and electromyographic (EMG) activity from ankle flexor (tibialis anterior, TA) and extensor (lateral gastrocnemius, LG) muscles. Using DeepLabCut pose estimation, we analyzed rhythmicity and limb coordination. We demonstrate steady rhythmic stepping of similar duration from P7 to P10 but with some fine-tuning of interlimb coordination with age. Hindlimb joints undergo a greater range of flexion at older ages, indicating maturation of flexion-extension cycles as the animal starts to walk. EMG recordings of TA and LG show alternation but with more focused activation particularly in the LG from P7 to P10. We discuss similarities to neonatal rat l-DOPA-induced air-stepping and infant assisted walking. We conclude that limb coordination and muscle activations recorded with this method represent basic spinal cord circuitry for limb control in neonates and pave the way for future investigations on the development of rhythmic limb control in genetic or disease models with correctly or erroneously developing motor circuitry.NEW & NOTEWORTHY We present novel methods to study neonatal air-stepping in newborn mice. These methods allow analyses at the onset of limb coordination during the period in which altricial species like rats, mice, and humans "learn" to walk. The methods will be useful to test a large variety of mutations that serve as models of motor disease in newborns or that are used to probe for specific circuit mechanisms that generate coordinated limb motor output.

Recovery of Volitional Motor Control and Overground Walking in Participants With Chronic Clinically Motor Complete Spinal Cord Injury: Restoration of Rehabilitative Function With Epidural Spinal Stimulation (RESTORES) Trial-A Preliminary Study.

Spinal cord injury (SCI) is damage to any part of the spinal cord resulting in paralysis, bowel and/or bladder incontinence, and loss of sensation and other bodily functions. Current treatments for chronic SCI are focused on managing symptoms and preventing further damage to the spinal cord with limited neuro-restorative interventions. Recent research and independent clinical trials of spinal cord stimulation (SCS) or intensive neuro-rehabilitation including neuro-robotics in participants with SCI have suggested potential malleability of the neuronal networks for neurological recovery. We hypothesize that epidural electrical stimulation (EES) delivered via SCS in conjunction with mental imagery practice and robotic neuro-rehabilitation can synergistically improve volitional motor function below the level of injury in participants with chronic clinically motor-complete SCI. In our pilot clinical RESTORES trial (RESToration Of Rehabilitative function with Epidural spinal Stimulation), we investigate the feasibility of this combined multi-modal approach in restoring volitional motor control and achieving independent overground locomotion in participants with chronic motor complete thoracic SCI. Secondary aims are to assess the safety of this combination therapy including the off-label SCS usage as well as improving functional outcome measures. To our knowledge, this is the first clinical trial that investigates the combined impact of this multi-modal EES and rehabilitation strategy in participants with chronic motor complete SCI. Two participants with chronic motor-complete thoracic SCI were recruited for this pilot trial. Both participants have successfully regained volitional motor control below their level of SCI injury and achieved independent overground walking within a month of post-operative stimulation and rehabilitation. There were no adverse events noted in our trial and there was an improvement in post-operative truncal stability score. Results from this pilot study demonstrates the feasibility of combining EES, mental imagery practice and robotic rehabilitation in improving volitional motor control below level of SCI injury and restoring independent overground walking for participants with chronic motor-complete SCI. Our team believes that this provides very exciting promise in a field currently devoid of disease-modifying therapies.

Unsupervised learning for real-time and continuous gait phase detection.

Individuals with lower limb impairment after a stroke or spinal cord injury require rehabilitation, but traditional methods can be challenging for both patients and therapists. Robotic systems have been developed to help; however, they currently cannot detect the continuous gait phase in real time, hindering their effectiveness. To address this limitation, researchers have attempted to develop gait phase detection in general using fuzzy logic algorithms and neural networks. However, there is a paucity of research on real-time and continuous gait phase detection. In light of this gap, we propose an unsupervised learning method for real-time and continuous gait phase detection. This method employs windows of real-time trajectories and a pre-trained model, utilizing trajectories from treadmill walking data, to detect the real-time and continuous gait phase of human on overground locomotion. The neural network model that we have developed exhibits an average time error of less than 11.51 ms across all walking conditions, indicating its suitability for real-time applications. Specifically, the average time error during overground walking at different speeds is 11.20 ms, which is comparatively lower than the average time error observed during treadmill walking, where it is 12.42 ms. By utilizing this method, we can predict the real-time phase using a pre-trained model from treadmill walking data collected with a full motion capture system, which can be performed in a laboratory setting, thereby eliminating the need for overground walking data, which can be more challenging to obtain due to the complexity of the setting.

Multifractality in stride-to-stride variations reveals that walking involves more movement tuning and adjusting than running

Introduction: The seemingly periodic human gait exhibits stride-to-stride variations as it adapts to the changing task constraints. The optimal movement variability hypothesis (OMVH) states that healthy stride-to-stride variations exhibit “fractality”—a specific temporal structure in consecutive strides that are ordered, stable but also variable, and adaptable. Previous research has primarily focused on a single fractality measure, “monofractality.” However, this measure can vary across time; strideto-stride variations can show “multifractality.” Greater multifractality in stride-tostride variations would highlight the ability to tune and adjust movements more.Methods: We investigated monofractality and multifractality in a cohort of eight healthy adults during self-paced walking and running trials, both on a treadmill and overground. Footfall data were collected through force-sensitive sensors positioned on their heels and feet. We examined the effects of self-paced walking vs. running and treadmill vs. overground locomotion on the measure of monofractality, α-DFA, in addition to the multifractal spectrum width, W, and the asymmetry in the multifractal spectrum, WAsym, of stride interval time series.Results: While the α-DFA was larger than 0.50 for almost all conditions, α-DFA was higher in running and locomoting overground than walking and locomoting on a treadmill. Similarly, W was greater while locomoting overground than on a treadmill, but an opposite trend indicated that W was greater in walking than running. Larger WAsym values in the negative direction suggest that walking exhibits more variation in the persistence of shorter stride intervals than running. However, the ability to tune and adjust movements does not differ between treadmill and overground, although both exhibit more variation in the persistence of shorter stride intervals.Discussion: Hence, greater heterogeneity in shorter than longer stride intervals contributed to greater multifractality in walking compared to running, indicated by larger negative WAsym values. Our results highlight the need to incorporate multifractal methods to test the predictions of the OMVH.

Activity of cat premotor cortex neurons during visually guided stepping.

Visual control of steps is critical in everyday life. Several motor centers are implicated in visual control of steps on a complex surface, however, participation of a large cortical motor area, the premotor cortex, in visual guidance of steps during overground locomotion has not been examined. Here, we analyzed the activity of neurons in feline premotor cortex areas 6aα and 6aγ as cats walked on the flat surface where visual guidance of steps is not needed and stepped on crosspieces of a horizontally placed ladder or over barriers where visual control of steps is required. The comparison of neuronal firing between vision-dependent and vision-independent stepping revealed components of the activity related to visual guidance of steps. We found that the firing activity of 59% of neurons was modulated with the rhythm of strides on the flat surface, and the activity of 83-86% of the population changed upon transition to locomotion on the ladder or with barriers. The firing rate and the depth of the stride-related activity modulation of 33-44% of neurons changed, and the stride phases where neurons preferred to fire changed for 58-73% of neurons. These results indicate that a substantial proportion of areas 6aα and 6aγ neurons is involved in visual guidance of steps. Compared with the primary motor cortex, the proportion of cells, the firing activity of which changed upon transition from vision-independent to vision-dependent stepping, was lower and the preferred phases of the firing activity changed more often between the tasks.NEW & NOTEWORTHY Visual control of steps is critical for daily living, however, how it is achieved is not well understood. Here, we analyzed how neurons in the premotor cortex respond to the demand for visual control of steps on a complex surface. We conclude that premotor cortex neurons participate in the cortical network supporting visual control of steps by modifying the phase, intensity, and salience of their firing activity.

Spinal control of locomotion before and after spinal cord injury

Thoracic spinal cord injury affects long propriospinal neurons that interconnect the cervical and lumbar enlargements. These neurons are crucial for coordinating forelimb and hindlimb locomotor movements in a speed-dependent manner. However, recovery from spinal cord injury is usually studied over a very limited range of speeds that may not fully expose circuitry dysfunction. To overcome this limitation, we investigated overground locomotion in rats trained to move over an extended distance with a wide range of speeds both pre-injury and after recovery from thoracic hemisection or contusion injuries. In this experimental context, intact rats expressed a speed-dependent continuum of alternating (walk and trot) and non-alternating (canter, gallop, half-bound gallop, and bound) gaits. After a lateral hemisection injury, rats recovered the ability to locomote over a wide range of speeds but lost the ability to use the highest-speed gaits (half-bound gallop and bound) and predominantly used the limb contralateral to the injury as lead during canter and gallop. A moderate contusion injury caused a greater reduction in maximal speed, loss of all non-alternating gaits, and emergence of novel alternating gaits. These changes resulted from weak fore–hind coupling together with appropriate control of left–right alternation. After hemisection, animals expressed a subset of intact gaits with appropriate interlimb coordination even on the side of the injury, where the long propriospinal connections were severed. These observations highlight how investigating locomotion over the full range of speeds can reveal otherwise hidden aspects of spinal locomotor control and post-injury recovery.

Neuromechanical Strategies for Obstacle Negotiation during Overground Locomotion following Incomplete Spinal Cord Injury in Adult Cats.

Following incomplete spinal cord injury in animals, including humans, substantial locomotor recovery can occur. However, functional aspects of locomotion, such as negotiating obstacles, remains challenging. We collected kinematic and electromyography data in 10 adult cats (5 males, 5 females) before and at weeks 1-2 and 7-8 after a lateral mid-thoracic hemisection on the right side of the cord while they negotiated obstacles of three different heights. Intact cats always cleared obstacles without contact. At weeks 1-2 after hemisection, the ipsilesional right hindlimb contacted obstacles in ∼50% of trials, triggering a stumbling corrective reaction or absent responses, which we termed Other. When complete clearance occurred, we observed exaggerated ipsilesional hindlimb flexion when crossing the obstacle with contralesional Left limbs leading. At weeks 7-8 after hemisection, the proportion of complete clearance increased, Other responses decreased, and stumbling corrective reactions remained relatively unchanged. We found redistribution of weight support after hemisection, with reduced diagonal supports and increased homolateral supports, particularly on the left contralesional side. The main neural strategy for complete clearance in intact cats consisted of increased knee flexor activation. After hemisection, ipsilesional knee flexor activation remained, but it was insufficient or more variable as the limb approached the obstacle. Intact cats also increased their speed when stepping over an obstacle, an increase that disappeared after hemisection. The increase in complete clearance over time after hemisection paralleled the recovery of muscle activation patterns or new strategies. Our results suggest partial recovery of anticipatory control through neuroplastic changes in the locomotor control system.SIGNIFICANCE STATEMENT Most spinal cord injuries (SCIs) are incomplete and people can recover some walking functions. However, the main challenge for people with SCIs that do recover a high level of function is to produce a gait that can adjust to everyday occurrences, such as turning, stepping over an obstacle, etc. Here, we use the cat model to answer two basic questions: How does an animal negotiate an obstacle after an incomplete SCI and why does it fail to safely clear it? We show that the inability to clear an obstacle is because of improper activation of muscles that flex the knee. Animals recover a certain amount of function thanks to new strategies and changes within the nervous system.

Comment on ‘The immediate effect of water treadmill walking exercise on overground in-hand walking locomotion in the horse’

To the editor We were pleased to see that the latest edition of the Comparative Exercise Physiology (2022; 18(5)) included a study on the topic of water treadmill exercise in horses. The literature in this field is scarce and there is a need to provide more scientific evidence on the use and protocols of water treadmill exercise in horses. We were however disappointed when we read the article entitled ‘The immediate effect of water treadmill walking exercise on overground in-hand walking locomotion in the horse’ by Tranquille et al. published in Comparative Exercise Physiology (2022; 18: 413-418) and wanted to bring some points to the attention of the readers and the authors.

The immediate effect of water treadmill walking exercise on overground in-hand walking locomotion in the horse

Water treadmill (WT) exercise is frequently used for training/rehabilitation of horses but the effect of WT exercise on short-term movement patterns is yet to be investigated. The objective of this study was to determine the immediate effect of WT exercise on overground limb and back kinematics. Six horses (mean ± standard deviation., age 15±6.5 years, height 164±2 cm and weight 539±37 kg) walked twice in a straight line, led from both sides, before and after a standardised WT exercise session (19 min duration; speed 1.6 m/s; water depths: 0.0/7.5/21.0/32.0/47.0 cm) on a flat concrete surface. Horses wore five inertial-measurement-units to determine poll/wither/pelvic displacement, and 10 anatomical markers to determine fetlock/carpal/tarsal joint angles at specific stride points. Degree of mediolateral tarsal oscillation during stance was graded. Wilcoxon-signed-rank tests were used to investigate differences between pre- and post-WT exercise for each variable. Post-WT exercise, there was a significant decrease in hindlimb fetlock extension at mid-stance compared with pre-WT exercise. No significant changes in movement patterns of the poll/withers/pelvis were detected post-WT exercise. In all horses there was greater mediolateral tarsal oscillation during the stance phase of the stride post-WT exercise, which could relate to muscle fatigue. The results suggest that a 19-min WT session has an effect on immediately-following overground in-hand walking locomotion patterns. Further work is required to determine the duration of this effect, and how different WT speeds and water depths affect locomotion patterns.

Acute Systemic White Blood Cell Changes following Degenerative Cervical Myelopathy (DCM) in a Mouse Model.

Degenerative cervical myelopathy (DCM) is caused by age-related degeneration of the cervical spine, causing chronic spinal cord compression and inflammation. The aim of this study was to assess whether the natural progression of DCM is accompanied by hematological changes in the white blood cell composition. If so, these changes can be used for diagnosis complementing established imaging approaches and for the development of treatment strategies, since peripheral immunity affects the progression of DCM. Gradual compression of the spinal cord was induced in C57B/L mice at the C5-6 level. The composition of circulating white blood cells was analyzed longitudinally at four time points after induction of DCM using flow cytometry. At 12 weeks, serum cytokine levels were measured using a Luminex x-MAP assay. Neurological impairment in the mouse model was also assessed using the ladder walk test and CatWalk. Stepping function (* p < 0.05) and overground locomotion (*** p < 0.001) were impaired in the DCM group. Importantly, circulating monocytes and T cells were affected primarily at 3 weeks following DCM. T cells were two-fold lower in the DCM group (*** p < 0.0006), whereas monocytes were four-fold increased (*** p < 0.0006) in the DCM compared with the sham group. Our data suggest that changes in white blood cell populations are modest, which is unique to other spinal cord pathologies, and precede the development of neurobehavioral symptoms.

The role of the visual environment on characteristics of over-ground locomotion in natural and virtual environments

Recent studies have suggested fundamental differences in the way that visual information is processed in virtual environments when compared to natural environments. To better understand these differences, we asked 20 young adults to walk in a real hallway featuring a mobile wall, which allowed three hallway width conditions: narrow (1.14 m), medium (1.31 m) and wide (1.48 m). A separate group of 21 young adults walked in a virtual hallway that closely replicated the real hallway. We were interested in determining (1) whether gait parameters and their variability would be similar between the natural and virtual environments, (2) whether visual information about the width of the hallway would affect gait performance in the two environments, and (3) whether the influence of hallway width would be similar in both environments. We hypothesized that because visual processing is fundamentally different in natural and virtual environments, spatiotemporal gait parameters would also be different in the two environments. Further, we hypothesized that gait and gait variability would be differentially affected by the manipulation of hallway width in the natural and virtual environments. Results indicated participants in the VR environment walked with decreased cadence, spent more time with both feet on the ground, and walked with more variability than participants in the natural environment. Further, several subtle but important differences were found regarding the effect of hallway width on gait in the two environments. In particular, the width of the hallway differentially affected cadence and normalized gait velocity between the real world and VR. These fundamental differences indicate more cautious gait in VR and could have significant implications when we consider how and when we use VR for rehabilitation, training and assessment.

Treadmill vs. overground trotting - a comparison of two kinetic measurement systems

Force plates are considered the gold standard for kinetic gait analysis, benefiting from measuring three-dimensional ground reaction forces. Nevertheless, the major disadvantage is that many trials are required during overground locomotion to capture adequate single-limb contacts. Additionally, the dogs slightly change velocities during overground walking, influencing kinetic and kinematic gait parameters. An alternative is using an instrumented treadmill that benefits from capturing many steady-state gait cycles at a constant speed quickly. The goal of this study was (1) to compare overground with treadmill locomotion and (2) to compare the instrumented treadmill with force plates for dogs kinetics measurements.Twelve client-owned dogs were measured during treadmill trotting while the treadmill was placed on force plates. Additionally, the dogs were measured during trotting along an alley over eight force plates. Bland-Altman plots, Pearson's (r), and concordance correlation coefficients (rc) were computed to explore the relative and general agreement between the measurement methods and overground and treadmill trotting.Overground and treadmill trotting gave an excellent agreement in peak vertical forces and impulses (r > 0.9, rc > 0.9). The instrumented treadmill showed similar force-time curves in shape and size and provided an excellent congruity for all parameters compared to force plates (r > 0.8, rc > 0.8).As a reliable tool in measuring key gait parameters, the instrumented treadmill may benefit from fast and reproducible data comparable to overground trotting.

QS63. Severity of Neuropathic Pain, Sensorimotor Impairments, and Sensory Neuron Abnormalities in Rat Model of Radiation Induced Neuropathy is Dose Dependent

Purpose: Radiation therapy (XRT) is one of the mainstays of cancer treatment, with approximately 50% of cancer patients requiring XRT as part of their treatment regimen. Of these patients, almost 31% subsequently suffer from debilitating neuropathic pain and sensory nerve abnormalities. XRT induced peripheral neuropathy results in progressive, intractable, and often irreversible nerve pain which can have a devastating effect on patients’ quality of life and potentially reduce the overall benefit of the therapy itself. We have previously established a novel rodent model of radiation induced peripheral neuropathy. The purpose of the present study was to assess neuropathic pain, sensorimotor impairments, and sensory neuron abnormalities in both clinically relevant and clinically high dose radiated animals. Methods: Eighteen male Lewis rats were randomly assigned to one of three experimental groups: (1) radiation of 35 Gray (Gy) divided into 5 daily doses of 7 Gy/day; (2) radiation of 70 Gray divided into 5 daily doses of 14 Gy/day, and (3) sham-radiated controls. All animals were tested at baseline in both pain and sensorimotor behavioral tests. Pain related measures included mechanical allodynia (von Frey test), cold allodynia (Acetone test), and thermal allodynia (Hargreaves test). Sensorimotor testing consisted of evaluation of overground locomotion using walkings tracks with calculation of the Sciatic Functional Index (SFI). Animals were tested serially over an 8 week period. At study endpoint, we performed nerve conduction analysis, electromyography (EMG), muscle force measurements, and all sciatic nerves were taken for histological/histomorphometrical analysis. In a separate cohort of animals, retrograde labeling was conducted in order to assess the level of sensory neuron death following radiation. Results: All animals that underwent radiation displayed significantly greater hypersensitivity to mechanical stimulation as compared to sham-radiated animals, indicative of chronic neuropathic pain. SFI values indicated sensorimotor impairments in radiated animals, and significantly lower twitch and tetanic muscle forces. Sensory neuron abnormalities and cell death were greater in radiated animals, with the high dose group displaying the most severe decrease. Conclusion: Results from this study demonstrate that neuropathic pain, sensorimotor behavioral impairment, and sensory neuron abnormalities vary as a function of radiation dose administered. Ongoing research is currently assessing novel therapeutic compounds to attenuate debilitating radiation induced sequelae, with the goal of improving the quality of life for cancer patients undergoing XRT.

Near-Fall Detection in Unexpected Slips during Over-Ground Locomotion with Body-Worn Sensors among Older Adults.

Slip-induced falls are a growing health concern for older adults, and near-fall events are associated with an increased risk of falling. To detect older adults at a high risk of slip-related falls, this study aimed to develop models for near-fall event detection based on accelerometry data collected by body-fixed sensors. Thirty-four healthy older adults who experienced 24 laboratory-induced slips were included. The slip outcomes were first identified as loss of balance (LOB) and no LOB (NLOB), and then the kinematic measures were compared between these two outcomes. Next, all the slip trials were split into a training set (90%) and a test set (10%) at sample level. The training set was used to train both machine learning models (n = 2) and deep learning models (n = 2), and the test set was used to evaluate the performance of each model. Our results indicated that the deep learning models showed higher accuracy for both LOB (>64%) and NLOB (>90%) classifications than the machine learning models. Among all the models, the Inception model showed the highest classification accuracy (87.5%) and the largest area under the receiver operating characteristic curve (AUC), indicating that the model is an effective method for near-fall (LOB) detection. Our approach can be helpful in identifying individuals at the risk of slip-related falls before they experience an actual fall.

Homing tasks and distance matching tasks reveal different types of perceptual variables associated with perceiving self-motion during over-ground locomotion.

Self-motion perception refers to the ability to perceive how the body is moving through the environment. Perception of self-motion has been shown to depend upon the locomotor action patterns used to move the body through the environment. Two separate lines of enquiry have led to the establishment of two distinct theories regarding this effect. One theory has proposed that distances travelled during locomotion are perceived via higher order perceptual variables detected by the haptic perceptual system. This theory proposes that two higher order haptic perceptual variables exist, and that the implication of one of these variables depends upon the type of gait pattern that is used. A second theory proposes that self-motion is perceived via a higher order perceptual variable termed multimodally specified energy expenditure (MSEE). This theory proposes that the effect of locomotor actions patterns upon self-motion perception is related to changes in the metabolic cost of locomotion per unit of perceptually specified traversed distance. Here, we test the hypothesis that the development of these distinct theories is the result of different choices in methodology. The theory of gait type has been developed based largely on the results of homing tasks, whereas the effect of MSEE has been developed based on the results of distance matching tasks. Here we test the hypothesis that the seemly innocuous change in experimental design from using a homing task to using a distance matching task changes the type of perceptual variables implicated in self-motion perception. To test this hypothesis, we closely replicated a recent study of the effect of gait type in all details bar one-we investigated a distance matching task rather than a homing task. As hypothesized, this change yielded results consistent with the predictions of MSEE, and distinct from gait type. We further show that, unlike the effect of gait type, the effect of MSEE is unaffected by the availability of vision. In sum, our findings support the existence of two distinct types of higher order perceptual variables in self-motion perception. We discuss the roles of these two types of perceptual variables in supporting effective human wayfinding.

The Role of the Visual Environment on Characteristics of Over-Ground Locomotion in Natural and Virtual Environments

The Role of the Visual Environment on Characteristics of Over-Ground Locomotion in Natural and Virtual Environments

Is coordination variability using vector coding different in overground and treadmill walking and running?

BackgroundCoordination variability has been linked to overuse running injuries and has been studied both on a treadmill and over-ground. It is not clear, however, if the coordination variability data from over-ground locomotion can be compared with treadmill locomotion data. Research questionTherefore, the purpose of this study was to compare coordination variability of selected lower extremity couplings at different locomotor speeds during over-ground and treadmill walking and running. MethodsNineteen (10 female, 9 male) healthy, recreational collegiate runners participated in this study. Each participant performed in two different conditions: over-ground and on a treadmill at three walking speeds (1.2, 1.6, and 2.0 m•s−1) and three running speeds (2.8, 3.2, and 3.6 m•s−1). A modified vector coding technique was used to calculate coordination variability for five selected coupled segment and joint angles. Each of the segmental couples was analyzed separately using a two-way repeated measures ANOVA (Condition Χ Speed) implemented with one-dimensional statistical parametric mapping. ResultsWhile no interaction effects were observed for condition X speed, we saw increased coordination variability in the sagittal couples during overground compared with treadmill locomotion, which predominantly occurred during the stance phase. There were mixed results for changes in coordination variability as a function of gait speed. However, for the sagital plane couplings, coordination variability decreased with speed, particularly during the stance phase. SignificanceThese results suggest that the controlled belt speed of the treadmill affects the intrinsic dynamics of human movement and this should be considered when making comparisons between treadmill and over-ground studies and in future study designs.

Wearable Sensor-Based Step Length Estimation During Overground Locomotion Using a Deep Convolutional Neural Network.

Step length is a critical gait parameter that allows a quantitative assessment of gait asymmetry. Gait asymmetry can lead to many potential health threats such as joint degeneration, difficult balance control, and gait inefficiency. Therefore, accurate step length estimation is essential to understand gait asymmetry and provide appropriate clinical interventions or gait training programs. The conventional method for step length measurement relies on using foot-mounted inertial measurement units (IMUs). However, this may not be suitable for real-world applications due to sensor signal drift and the potential obtrusiveness of using distal sensors. To overcome this challenge, we propose a deep convolutional neural network-based step length estimation using only proximal wearable sensors (hip goniometer, trunk IMU, and thigh IMU) capable of generalizing to various walking speeds. To evaluate this approach, we utilized treadmill data collected from sixteen able-bodied subjects at different walking speeds. We tested our optimized model on the overground walking data. Our CNN model estimated the step length with an average mean absolute error of 2.89 ± 0.89 cm across all subjects and walking speeds. Since wearable sensors and CNN models are easily deployable in real-time, our study findings can provide personalized real-time step length monitoring in wearable assistive devices and gait training programs.