Straight Walking Research Articles

Generation of Turning Walking Motion for Biped Robot based on Optimization Method

Biped robots are expected to be able to operate in a human living environment. It is necessary to generate autonomous walking, such as avoiding and overcoming obstacles to adapting to various environments with and maintaining stability. The walking behavior of biped robots is determined by the landing point coordinates and the time of each support period. Optimization using genetic algorithms can derive the optimal walking motion based on minimizing energy consumption and walking time with stability. The purpose of this study is to generate biped robot gait including obstacle avoidance motion. The genetic algorithm optimization used to generate a straight walking motion is extended and applied to generate a turning motion. The waist trajectory is made into a three-dimensional curve to smooth the connection between each gait and reduce energy consumption. Assuming that the walking environment with obstacles has been identified, the effectiveness of this method is demonstrated by the results of generating turning motions for several environments.

The Validity and Reliability of Six Minute Walk Test in a 15 Meter Track

ABSTRACTIntroduction: Endurance is one of the key fitness measure that should be evaluated daily. Clinicalassessment of endurance in daily practice is usually hurdled by limitation of hospital spaces. Anotherobstacle arise that shorter six-minute walk test (6MWT) track will lead to more turning motion, yieldingshorter straight walking distance with increased ener gy expenditure.Methods: This cross sectional study compares 6MWT on a 15 meter corridor, to the gold standardBiodex® gait trainer for healthy adults aged 18-50 years. Subjects without any anatomical abnormalitiesor systemic disorders were recruited, and instructed to turn in a three-step method at track ends tomaximize walking distance. Furthermore, validity and reliability assessments to obtain both Pearsoncorrelation and Cronbach Alpha values were performed respectively.Results: Among 123 subjects, 58 males aged ranging from 18 to 45 years, and females between 18 to42 years were recruited. Anthropometrical values were similar between gender. Significant differencein walking distance and walking speed was observed. Comparison of walking distance between the twomodalities were seen to be statistically similar (p=0.693). Pearson validity test was proven significant (p<0.001) with a correlation coefficient of r = 0.998, while reliability test obtained Cronbach’s Alpha valueof 0.999, hence showing that these are both valid and reliable.Conclusion: Good validity and reliability of 6MWT in 15 meter track as compared to the gold standardBiodex® gait trainer was demonstrated in this study. Moreover, shorter track is a potential modificationadhering to the limitation of operational space. The three-step turning method could significantlyimproves total walk distance, and thus is suggested.Keywords: clinical assessment, endurance, six-minute walk test, walk dist ance, walking speed

Using a Portable Gait Rhythmogram to Examine the Effect of Music Therapy on Parkinson's Disease-Related Gait Disturbance.

External cues improve walking by evoking internal rhythm formation related to gait in the brain in patients with Parkinson’s disease (PD). This study examined the usefulness of using a portable gait rhythmogram (PGR) in music therapy on PD-related gait disturbance. A total of 19 subjects with PD who exhibited gait disturbance were evaluated for gait speed and step length during a 10 m straight walking task. Moreover, acceleration, cadence, and trajectory of the center of the body were estimated using a PGR. Walking tasks were created while incorporating music intervention that gradually increased in tempo from 90 to 120 beats per minute (BPM). We then evaluated whether immediate improvement in gait could be recognized even without music after walking tasks by comparing pre- (pre-MT) and post-music therapy (post-MT) values. Post-MT gait showed significant improvement in acceleration, gait speed, cadence, and step length. During transitions throughout the walking tasks, acceleration, gait speed, cadence, and step length gradually increased in tasks with music. With regard to the trajectory of the center of the body, we recognized a reduction in post-MT medio-lateral amplitude. Music therapy immediately improved gait disturbance in patients with PD, and the effectiveness was objectively shown using PGR.

Differences in walking-to-turning characteristics between older adult fallers and nonfallers: a prospective and observational study using wearable inertial sensors.

Wearable inertial sensors have gradually been used as an objective technology for biomechanical assessments of both healthy and pathological movement patterns. This paper used foot-worn sensors for characterizing the spatiotemporal characteristics of walking and turning between older fallers and nonfallers. Thirty community-dwelling older fallers and 30 older nonfallers performed 10-m straight walking, turned 180° around a cone, and then walked 10-m back to the starting point. Specific algorithms were used to measure spatiotemporal gait (double support phase of the gait cycle, swing width, and minimal toe clearance) and turning parameters (turn duration and turn steps) using two foot-worn Physiolog inertial sensor system. The researchers directly exported data as reported by the system. Our findings indicated that older fallers showed 26.58% longer time (P = 0.036) and 13.21% more steps (P = 0.038) compared to nonfallers during turning. However, both groups decreased their walking velocity (both P < 0.001), increased double support (both P = 0.001), and increased the swing width (both P = 0.001) during the transition from walking to turning. The older nonfallers additionally increased toe clearance (P = 0.001). Compared with the fallers, the older nonfallers showed a larger change in the swing width (P = 0.025) and toe clearance (P = 0.025) in walking to turning. Older fallers may adopt a cautionary strategy while turning to reduce the risk of falls. Wearable sensors can provide the temporospatial characteristics of turning and reveal significant differences by fall status, indicating the potential of turning measures as possible markers for identifying those at fall risk.

Locomotion Control With Frequency and Motor Pattern Adaptations.

Existing adaptive locomotion control mechanisms for legged robots are usually aimed at one specific type of adaptation and rarely combined with others. Adaptive mechanisms thus stay at a conceptual level without their coupling effect with other mechanisms being investigated. However, we hypothesize that the combination of adaptation mechanisms can be exploited for enhanced and more efficient locomotion control as in biological systems. Therefore, in this work, we present a central pattern generator (CPG) based locomotion controller integrating both a frequency and motor pattern adaptation mechanisms. We use the state-of-the-art Dual Integral Learner for frequency adaptation, which can automatically and quickly adapt the CPG frequency, enabling the entire motor pattern or output signal of the CPG to be followed at a proper high frequency with low tracking error. Consequently, the legged robot can move with high energy efficiency and perform the generated locomotion with high precision. The versatile state-of-the-art CPG-RBF network is used as a motor pattern adaptation mechanism. Using this network, the motor patterns or joint trajectories can be adapted to fit the robot's morphology and perform sensorimotor integration enabling online motor pattern adaptation based on sensory feedback. The results show that the two adaptation mechanisms can be combined for adaptive locomotion control of a hexapod robot in a complex environment. Using the CPG-RBF network for motor pattern adaptation, the hexapod learned basic straight forward walking, steering, and step climbing. In general, the frequency and motor pattern mechanisms complement each other well and their combination can be seen as an essential step toward further studies on adaptive locomotion control.

Effect of gait protocols and postoperative shoes on off-loading of forefoot in preoperative patients for forefoot disorders.

The purpose of this study was to clarify the effect of gait protocols and postoperative shoes on forefoot load in preoperative patients for forefoot disorders and compare footwear comfort between different types of postoperative shoes. Fourteen subjects scheduled to undergo forefoot surgeries were recruited. The maximum force under the forefoot region was measured during 10 m straight walking in two gait patterns with six different shoe types. Visual analogue scale (VAS) scores for footwear comfort, subjective lower thigh pain, and electrical activities of lower thigh muscles were also evaluated. The body weight-normalized maximum force under the forefoot region significantly decreased in step-to gait compared to normal gait regardless of the shoe types used. Under the same gait condition, no significant difference was observed in the forefoot off-loading effect between the different shoe types used. Significantly worse VAS scores, significantly higher tibialis anterior muscle activities, and complaints of lower thigh pain were demonstrated in the gait with the reverse camber shoe. Gait protocol of step-to gait had more forefoot off-loading effect than postoperative shoes. The forefoot off-loading effect did not differ among the postoperative shoes, suggesting that postoperative shoes can be selected with an emphasis on footwear comfort.

An inertial sensor-based algorithm for turning detection during gait.

Patients with Parkinson's disease (PD) can be divided into two subtypes based on clinical features, namely tremor-dominant (TD) and postural instability and gait difficulty (PIGD). Detection of PIGD symptoms is crucial for early diagnosis of PD and timely clinical intervention. However, patients at the early stage may not exhibit obvious motor dysfunctions during normal straight walking leading to difficulties in PD identification. Researchers have found that patients would show significant motor deteriorations in turning due to their cognition limitation. Therefore, turning detection is essential for quantitative motion analysis in the gait assessment of PD patients. In this study, we proposed a novel inertial-sensor-based algorithm for turning detection. Ten healthy young participants were enrolled in the experiment where they were required to walk along a 7-meter pathway with two 180 degree turns at their comfortable walking speed. Five inertial sensors were attached to the upper trunk, the shank and the foot of both legs. The algorithm performance was validated using an optical motion capture system for reference and two sensor combination options (upper trunk and shank sensors, upper trunk and foot sensors) were compared. The results showed that the proposed algorithm achieved accuracy over 98% for identifying the turning state of both legs. The integration of the upper trunk and foot sensors had no significant effect on the detection accuracy compared to that with the use of the upper trunk and shank sensors. Our algorithm has the potential to be implemented in the motion analysis model for complicated gait tasks, which has great potential in the early diagnosis of PIGD.

Pheromone binding protein is involved in temporal olfactory resolution in the silkmoth

SummaryMale moths utilize spatio-temporal female sex pheromone information to orient toward conspecific females. Pheromones are distributed as discontinuous plumes owing to air turbulence; thus, efficient tracking of intermittent stimuli is expected to require a high temporal resolution. Here, using pheromone binding protein (BmPBP1)-knockout silkmoths, we showed that a loss of functional PBP lowered the temporal sensory resolution of male antennae. This altered temporal resolution resulted in significantly reduced straight walking and longer turning behavior, which respectively occurred when males detected and lost contact with pheromones, indicating that temporal resolution was also lowered at the behavioral level. BmPBP1-knockout males required significantly longer time than wild-type males in locating pheromone sources and female moths. Our results suggest that BmPBP1 plays a critical role in determining olfactory response kinetics. Accordingly, high temporal olfactory and behavioral resolutions, as shaped by PBP, are essential for tracking pheromone plumes and locating females efficiently.

Prevalence of Physical Activity with Mobility Disabilities among Senior Citizens in a Selected Old Home

The purpose of the study was to identify the mobility problem of aged people in selected old homes. The ages of the respondents are 60 plus age, which is clustered into 3 age groups 60-69 years, 70-79 years, and 80 plus age. This study established among 100% respondents 89.3% have self-bathing capacity, 89.3% have self-dressing capacity, 89.8% have self-toileting capacity, 93.3% have self-teeth washing capacity, 93.7% have self-eating capacity. For finding other problems of aged people set up among 206 participants of the old home area, 35.0% are disability problem. Besides, in old homes 19.9% have suffered diabetic mellitus for a long time, 51.0% suffered from hypertension, 11.7% suffered from low blood pressure, 14.6% have heart problems, 64.6% have urine catching difficulty, 6.8% have kidney disease. Among 206 respondents of the old home, area was 44.2% abnormal posture and they have 36.9% kyphosis, 4.4% scoliosis 0.5% lordosis, and 2.4% another abnormal posture. For the finding of aged people, we have asked some questions to identify pain severity and several labels found that among 206 participants of the old home area were 52.4% have pain during straight walking, 36.9% have neck pain, 56.3% have hip pain or lower back pain, 28.6% have thoraco-lumber pain and 34.0% have pain during sleeping time. Besides On this area respondents there was pain severity 21.4% have mild pain, 22.3% have moderate pain and 24.8% have severe pain. In this paper among 206 respondents of the old home area was 10.7% having a stroke history. Here 3.4% right side, 4.4 left sides, both sides 2.9% paralyzes. In this study Right shoulder motion 56.8% of participants ROM under 150 degrees and Left shoulder motion 61.2% of participants ROM under 150 degrees. Conversely, Right hip motion was 27.7% of participant's ROM under 60 degrees and Left hip motion 30.6% of participant's ROM under 60 degrees. Besides, Right knee motion 56.8% of participants ROM under 120 degrees and Left knee motion 57.3% participants ROM under 120 degrees. After completing the current study we think that everyone should take responsibility to survive the aged people for a long time.

Gait-Related Brain Activation During Motor Imagery of Complex and Simple Ambulation in Parkinson's Disease With Freezing of Gait.

Background: Freezing of gait (FOG) in Parkinson's disease (PD) is a devastating clinical phenomenon that has a detrimental impact on patients. It tends to be triggered more often during turning (complex) than during forwarding straight (simple) walking. The neural mechanism underlying this phenomenon remains unclear and requires further elucidation.Objective: To investigate the differences in cerebral functional magnetic resonance imaging responses between PD patients with and without FOG during explicitly video-guided motor imagery (MI) of various complex (normal, freezing) and simple (normal, freezing) walking conditions.Methods: We recruited 34 PD patients, namely, 20 with FOG and 14 without FOG, and 15 normal controls. Participants underwent video-guided MI of turning and straight walking, with and without freezing, while their brain blood oxygen level-dependent (BOLD) activities were measured. Gait analysis was performed.Results: While comparing FOG turning with FOG straight walking, freezers showed higher activation of the superior occipital gyrus, left precentral gyrus, and right postcentral gyrus compared with non-freezers. Normal controls also manifest similar findings compared with non-freezers, except no difference was noted in occipital gyrus activity between the two groups. Freezers also displayed a higher effect size in the locomotor regions than non-freezers during imagery of normal turning.Conclusions: Our findings suggest that freezers require a higher drive of cortical and locomotion regions to overcome the overinhibition of the pathways in freezers than in non-freezers. Compared with simple walking, increased dorsal visual pathway and deep locomotion region activities might play pivotal roles in tackling FOG in freezers during complex walking.

Gait and Balance Biomechanical Characteristics of Patients With Grades III and IV Hallux Rigidus

Patients with hallux rigidus (HR) tend to develop a characteristic alteration in walking to lessening pain and compensate for the limited range of motion at the first metatarsophalangeal (MTP1) joint that might be affected balance and gait. The goal of this study was to perform an integrated biomechanical description of gait and balance of symptomatic patients with either grade as III or IV HR in comparison with healthy subjects. Eleven patients (7 men) with HR (60 ± 7 years, 1.60 ± 0.07 m, and 70 ± 13 kg) and 16 (7 men) healthy subjects (70 ± 8 years, 1.66 ± 0.10 m, and 74 ± 14 kg) were included. Subjects performed 2 tasks: walking (5 trials of straight walking for at least 6 meters) and bipedal quiet standing for 30 seconds. For these 2 tasks the following variables were measured: range of motion of the MTP1 joint, plantar pressure distribution during the stance phase of walking, and the postural sway during quiet standing. Plantar pressure was measured in up 15 walking trials with a mat pressure sensor. The MTP1 joint range of motion for flexion/extension during walking was significantly smaller for the patients with HR than for the control group (HR: 14 ± 8°, control: 44 ± 5°; t(17) = -9.7, p < .001). The forefoot plantar pressure distribution among different regions of the foot in patients with HR was not statistically different than the control group, but there was a tendency of higher pressures in the lateral metatarsal heads (p = .06). As description of the postural sway during quiet standing, the center of pressure area was not different between HR and the control group (p > .05). Decreased MTP1 joint range of motion for flexion/extension during walking in symptomatic high-grade HR patients can be associated with higher pressure in the lateral metatarsal heads while the impact on postural sway is not affected.

Estimating Lower Body Kinematics Using a Lie Group Constrained Extended Kalman Filter and Reduced IMU Count

Goal: Gait monitoring is useful for diagnosing movement disorders or assessing surgical outcomes. This paper presents an algorithm for estimating pelvis, thigh, shank, and foot kinematics during walking using only two or three wearable inertial sensors. Methods: The algorithm makes novel use of a Lie-group-based extended Kalman filter. The algorithm iterates through the prediction (kinematic equation), measurement (pelvis position pseudo-measurements, zero-velocity update, and flat-floor assumption), and constraint update (hinged knee and ankle joints, constant leg lengths). Results: The inertial motion capture algorithm was extensively evaluated on two datasets showing its performance against two standard benchmark approaches in optical motion capture (i.e., plug-in gait (commonly used in gait analysis) and a kinematic fit (commonly used in animation, robotics, and musculoskeleton simulation)), giving insight into the similarity and differences between the said approaches used in different application areas. The overall mean body segment position (relative to mid-pelvis origin) and orientation error magnitude of our algorithm ( n=14 participants) for free walking was 5.93 ± 1.33 cm and 13.43 ±1.89 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> when using three IMUs placed on the feet and pelvis, and 6.35 ± 1.20 cm and 12.71 ±1.60 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> when using only two IMUs placed on the feet. Conclusion: The algorithm was able to track the joint angles in the sagittal plane for straight walking well, but requires improvement for unscripted movements (e.g., turning around, side steps), especially for dynamic movements or when considering clinical applications. Significance: This work has brought us closer to comprehensive remote gait monitoring using IMUs on the shoes. The low computational cost also suggests that it can be used in real-time with gait assistive devices.

Stabilization Strategies for Fast Walking in Challenging Environments With Incomplete Spinal Cord Injury.

Gait rehabilitation following incomplete spinal cord injury (iSCI) often aims to enhance speed and stability. Concurrently increasing both may be difficult though as certain stabilization strategies will be compromised at faster speeds. To evaluate the interaction between speed and lateral stability, we examined individuals with (n = 12) and without (n = 12) iSCI as they performed straight walking and lateral maneuvers at Preferred and Fast treadmill speeds. To better detect the effects of speed on stability, we challenged lateral stability with a movement amplification force field. The Amplification field, created by a cable-driven robot, applied lateral forces to the pelvis that were proportional to the real-time lateral center of mass (COM) velocity. While we expected individuals to maintain stability during straight walking at the Fast speed in normal conditions, we hypothesized that both groups would be less stable in the Amplification field at the Fast speed compared to the Preferred. However, we found no effects of speed or the interaction between speed and field on straight-walking stability [Lyapunov exponent or lateral margin of stability (MOS)]. Across all trials at the Fast speed compared to the Preferred, there was greater step width variability (p = 0.031) and a stronger correlation between lateral COM state at midstance and the subsequent lateral foot placement. These observations suggest that increased stepping variability at faster speeds may be beneficial for COM control. We hypothesized that during lateral maneuvers in the Amplification field, MOS on the Initiation and Termination steps would be smaller at the Fast speed than at the Preferred. We found no effect of speed on the Initiation step MOS within either field (p > 0.350) or group (p > 0.200). The Termination step MOS decreased at the Fast speed within the group without iSCI (p < 0.001), indicating a trade-off between lateral stability and forward walking speed. Unexpectedly, participants took more steps and time to complete maneuvers at the Fast treadmill speed in the Amplification field. This strategy prioritizing stability over speed was especially evident in the group with iSCI. Overall, individuals with iSCI were able to maintain lateral stability when walking fast in balance-challenging conditions but may have employed more cautious maneuver strategies.

Kinematic gait characteristics of straight line walk in clinically sound dairy cows.

The aim of this study is to describe the kinematic gait characteristics of straight line walk in clinically sound dairy cows using body mounted Inertial Measurement Units (IMUs) at multiple anatomical locations. The temporal parameters used are speed and non-speed normalized stance duration, bipedal and tripedal support durations, maximal protraction and retraction angles of the distal limbs and vertical displacement curves of the upper body. Gait analysis was performed by letting 17 dairy cows walk in a straight line at their own chosen pace while equipped with IMU sensors on tubera sacrale, left and right tuber coxae (LTC and RTC), back, withers, head, neck and all four lower limbs. Data intervals with stride by stride regularity were selected based on video data. For temporal parameters, the median was calculated and 95% confidence intervals (CI) were estimated based on linear mixed model (LMM) analysis, while for limb and vertical displacement curves, the median and most typical curves were calculated. The temporal parameters and distal limb angles showed consistent results with low variance and LMM analysis showed non-overlapping CI for all temporal parameters. The distal limb angle curves showed a larger and steeper retraction angle range for the distal front limbs compared with the hind limbs. The vertical displacement curves of the sacrum, withers, LTC and RTC showed a consistent sinusoidal pattern while the head, back and collar curves were less consistent and showed more variation between and within cows. This kinematic description might allow to objectively differentiate between normal and lame gait in the future and determine the best anatomical location for sensor attachment for lameness detection purposes.

Estimation of the body center of mass velocity during gait of people with transfemoral amputation from force plate data integration

BackgroundBody Center Of Mass velocity assessment is a prerequisite for several applications in prosthetic control and rehabilitation monitoring. Force plate data integration is a promising alternative to full-body quantitative analysis of segmental kinematics to estimate the velocity. Still, it remains to be implemented and validated for people with transfemoral amputation. MethodsTwo methods were used (force plate based and pelvic markers based) for Body Center Of Mass velocity estimation in a clinical context. The two methods were comparatively assessed on overground walking data of eight people with transfemoral amputation in a laboratory equipped with a motion capture system and force plates compared to reference estimation derived from a full body segmental gait analysis. The ‘Methods’ agreement with the reference was quantified from the Bland and Altman procedure. FindingsThe estimation of Body Center Of Mass velocity from force plate data integration was considered acceptable in terms of limits of agreement. In addition, the hypotheses used to determine integration constants were evaluated and shown to be reasonable as far as the walking direction is well controlled. InterpretationResults demonstrate the possibility to use the force plate method to assess the Body Center Of Mass velocity of people with transfemoral amputation for straight walking on level ground. An estimation from the velocity of pelvic markers can also be a relevant alternative as soon as the walking velocity remains low. Further investigation will deal with the impact of the errors on the computation of derived parameters such as individual limb power.

Evaluating the Impact of IMU Sensor Location and Walking Task on Accuracy of Gait Event Detection Algorithms.

There are several algorithms that use the 3D acceleration and/or rotational velocity vectors from IMU sensors to identify gait events (i.e., toe-off and heel-strike). However, a clear understanding of how sensor location and the type of walking task effect the accuracy of gait event detection algorithms is lacking. To address this knowledge gap, seven participants were recruited (4M/3F; 26.0 ± 4.0 y/o) to complete a straight walking task and obstacle navigation task while data were collected from IMUs placed on the foot and shin. Five different commonly used algorithms to identify the toe-off and heel-strike gait events were applied to each sensor location on a given participant. Gait metrics were calculated for each sensor/algorithm combination using IMUs and a reference pressure sensing walkway. Results show algorithms using medial-lateral rotational velocity and anterior-posterior acceleration are fairly robust against different sensor locations and walking tasks. Certain algorithms applied to heel and lower lateral shank sensor locations will result in degraded algorithm performance when calculating gait metrics for curved walking compared to straight overground walking. Understanding how certain types of algorithms perform for given sensor locations and tasks can inform robust clinical protocol development using wearable technology to characterize gait in both laboratory and real-world settings.

Performance during reactive handrail grasping during forward walking by young and older adults with and without prior knowledge of the direction of movement is correlated with grip strength.

It has been suggested that the most frequent cause of falls in assisted-living facilities is due to incorrect weight shifting. Lateral instability and weakness have also been linked to falls risk. The objective of this study was to evaluate balance responses to weight shifting during walking and to investigate age-related changes in movement and strength. Thirty-two participants (16 young, 16 older) completed 12 straight walking trials and 6 trials in each condition where a weight shift was required to grasp a handrail. Instructions were to walk down the pathway and, if cued, grasp the handrail as quickly as possible. Conditions included left and right grasping trials, with and without prior knowledge about the movement direction. Kinematic data were recorded and center of mass (COM) was calculated to examine whole body movements. A clinical balance test, strength, and body composition measures were captured to facilitate exploration into the relationship of these measures with reactive movements used during weight transfers. Young adults had quicker lateral COM velocities and reached peak velocity earlier. Males completed the task quicker than females and, for everyone, having knowledge about direction enabled quicker responses. Grip strength was correlated to most performance metrics in this study; more-so than body composition. Slower reactive movements might reflect a more cautious strategy in the older adults or it may highlight changes that occur with increased age and strength changes.

Fall risk classification for people with lower extremity amputations using random forests and smartphone sensor features from a 6-minute walk test.

Fall-risk classification is a challenging but necessary task to enable the recommendation of preventative programs for individuals identified at risk for falling. Existing research has primarily focused on older adults, with no predictive fall-risk models for lower limb amputees, despite their greater likelihood of fall-risk than older adults. In this study, 89 amputees with varying degrees of lower limb amputation were asked if they had fallen in the past 6 months. Those who reported at least one fall were considered a fall risk. Each participant performed a 6 minute walk test (6MWT) with an Android smartphone placed in a holder located on the back of the pelvis. A fall-risk classification method was developed using data from sensors within the smartphone. The Ottawa Hospital Rehabilitation Center Walk Test app captured accelerometer and gyroscope data during the 6MWT. From this data, foot strikes were identified, and 248 features were extracted from the collection of steps. Steps were segmented into turn and straight walking, and four different data sets were created: turn steps, straightaway steps, straightaway and turn steps, and all steps. From these, three feature selection techniques (correlation-based feature selection, relief F, and extra trees classifier ensemble) were used to eliminate redundant or ineffective features. Each feature subset was tested with a random forest classifier and optimized for the best number of trees. The best model used turn data, with three features selected by Correlation-based feature selection (CFS), and used 500 trees in a random forest classifier. The resulting metrics were 81.3% accuracy, 57.2% sensitivity, 94.9% specificity, a Matthews correlation coefficient of 0.587, and an F1 score of 0.83. Since the outcomes are comparable to metrics achieved by existing clinical tests, the classifier may be viable for use in clinical practice.

Continuous Classification of Locomotion in Response to Task Complexity and Anticipatory State.

ObjectiveIntent recognition in lower-extremity assistive devices (e.g., prostheses and exoskeletons) is typically limited to either recognition of steady-state locomotion or changes of terrain (e.g., level ground to stair) occurring in a straight-line path and under anticipated condition. Stability is highly affected during non-steady changes of direction such as cuts especially when they are unanticipated, posing high risk of fall-related injuries. Here, we studied the influence of changes of direction and user anticipation on task recognition, and accordingly introduced classification schemes accommodating such effects.MethodsA linear discriminant analysis (LDA) classifier continuously classified straight-line walking, sidestep/crossover cuts (single transitions), and cuts-to-stair locomotion (mixed transitions) performed under varied task anticipatory conditions. Training paradigms with varying levels of anticipated/unanticipated exposures and analysis windows of size 100–600 ms were examined.ResultsMore accurate classification of anticipated relative to unanticipated tasks was observed. Including bouts of target task in the training data was necessary to improve generalization to unanticipated locomotion. Only up to two bouts of target task were sufficient to reduce errors to <20% in unanticipated mixed transitions, whereas, in single transitions and straight walking, substantial unanticipated information (i.e., five bouts) was necessary to achieve similar outcomes. Window size modifications did not have a significant influence on classification performance.ConclusionAdjusting the training paradigm helps to achieve classification schemes capable of adapting to changes of direction and task anticipatory state.SignificanceThe findings could provide insight into developing classification schemes that can adapt to changes of direction and user anticipation. They could inform intent recognition strategies for controlling lower-limb assistive to robustly handle “unknown” circumstances, and thus deliver increased level of reliability and safety.

Unrestricted stride detection during stair climbing using IMUs

Stride detection, or the identification of the initial (IC) and terminal contact (TC) of the feet while walking, is important for gait analysis. Automatic stride detection based only on kinematic data is challenging, even when using portable, low-cost, user-friendly Inertial Measurement Units (IMUs). Although there are algorithms for straight walking available, they are often not applicable to other movement patterns. Furthermore, these algorithms are based on the use of different IMUs placed on different locations of the body with different pre-processing filters and rely on analyzing different measurement signals. Therefore, it is difficult to apply existing algorithms for specific study settings.To achieve a new algorithm, thirty-five healthy participants were analyzed during walking and stair climbing while kinematic motion data was measured using the IMU system MyoMotion. Based on the analysis of different published methods for IC and TC detection, a new robust stride detection algorithm was developed and validated in comparison with two different algorithms. From this, it was determined that the newly developed algorithm was successful in automatic stride detection during walking and ascending/ descending stairs with 100% detected gait events, while the other algorithms failed during stair climbing with only 44% and 91% detected gait events.