Gaze and motor behavior of people with PD during obstacle circumvention

The aim of this study was to analyze the motor and visual strategies used when walking around (circumvention) an obstacle in patients with Parkinson’s disease (PD), in addition to the effects of dopaminergic medication on these strategies. To answer the study question, people with PD (15) and neurologically healthy individuals (15 − CG) performed the task of obstacle circumvention during walking (5 trials of unobstructed walking and obstacle circumvention). The following parameters were analyzed: body clearance (longer mediolateral distance during obstacle circumvention of the center of mass -CoM- to the obstacle), horizontal distance (distance of the CoM at the beginning of obstacle circumvention to the obstacle), circumvention strategy (“lead-out” or “lead-in” strategy), spatial-temporal of each step, and number of fixations, the mean duration of the fixations and time of fixations according to areas of interest. In addition, the variability of each parameter was calculated. The results indicated that people with PD and the CG presented similar obstacle circumvention strategies (no differences between groups for body clearance, horizontal distance to obstacle, or obstacle circumvention strategy), but the groups used different adjustments to perform these strategies (people with PD performed adjustments during both the approach and circumvention steps and presented greater visual dependence on the obstacle; the CG adjusted only the final step before obstacle circumvention). Moreover, without dopaminergic medication, people with PD reduced body clearance and increased the use of a “lead-out” strategy, variability in spatial-temporal parameters, and dependency on obstacle information, increasing the risk of contact with the obstacle during circumvention.     

Reading text messages at different stages of pedestrian circumvention affects strategies for collision avoidance in young and older adults

BackgroundReading text messages is associated with accidents while walking in community places.Research questionTo what extent does reading text messages at different stages of obstacle circumvention affect avoidance strategies while walking in young vs. older adults?MethodsSixteen healthy young and 14 older adults were assessed while walking and viewing a virtual environment (VE) simulating a subway station with three virtual pedestrians positioned 7.5 m away from the participant in the centre (0°), left and right (±40°). As participants advanced 0.5 m towards a target in the far space, a virtual pedestrian randomly approached them. Text messages were delivered at onset of pedestrian movement (0.5 m; early message) or during obstacle circumvention (2.5 m; late message). A Vicon motion capture system captured trajectory displacement while walking.ResultsIn both age groups, accuracy of message report (AMR) was reduced for early compared to late messages (p < 0.001), although older adults showed larger deterioration (p < 0.001) compared to younger participants. Locomotor outcomes (obstacle clearance, onset time of avoidance and walking speed) showed no differences between young and older participants (p > 0.05). Early messages led to slower walking speed (p < 0.001) and more frequent collisions compared to late messages and the no-message condition. Late messages yielded faster walking speed (p < 0.001) and onset time of avoidance (p < 0.02) compared to the other conditions.SignificanceResults indicate that the stage of an avoidance strategy at which text messages are received impacts on pedestrian circumvention, with early messages posing a greater challenge to collision avoidance. In older adults, the reduced AMR suggests larger dual-task interference and prioritization of the walking task. The lack of further walking speed reduction in older vs. young adults may put them at greater risk of collisions in crowded, unpredictable community environments.     

Kinematic patterns of participants with a below-knee prosthesis stepping over obstacles of various heights during locomotion

The focus of this paper was to examine the lead limb preference and the kinematic patterns of the lead limb of participants with a unilateral below-knee prosthesis when stepping over obstacles of different heights. Firstly, ten unilateral below-knee amputees stepped over obstacles of three different heights placed in their walking path to determine if they had a lead limb preference. Five of the ten participants demonstrated a sound limb lead preference, two participants showed a prosthetic limb lead preference and three showed no preference at all. Seven of these participants subsequently stepped over obstacles of six different heights leading with their sound or prosthetic limb as observed in the first experiment, while whole body kinematic data were collected. Relative joint angles of the stance and swing limb were calculated when the swing limb was over the obstacle. Swing hip elevation and hip and knee flexion increased as functions of obstacle height. Stance limb hip flexion, knee flexion and (on the sound side) ankle plantarflexion increased slightly with increasing obstacle height, but stance limb hip elevation did not. Therefore, it appears that these stance limb modulations served to position the pelvis further back from the obstacle as obstacle height increased. The posterior shell of the prosthetic socket limited residual limb swing knee flexion, and the increased ankle dorsiflexion seen on the lead sound side was not present on the lead prosthetic side. These limitations were associated with increased swing prosthetic foot angle and increased stance ankle plantarflexion. These results provide insights into the adaptability of the locomotor system, and have implications for lower extremity prosthetic design and amputee rehabilitation.     

Repeatability of surface EMG during gait in children

Although mean amplitude and ON–OFF timing of muscle recruitment and electromyography (EMG) activation during gait is achieved by an age of six to eight years in normally developing children, recruitment dynamics illustrated by the shape of the EMG waveform may require continued developmental practice to achieve a stable pattern. Previous analyses have quantified the repeatability of the EMG waveform in adult subjects, but EMG variability for a pediatric population may be significantly different. The goal of this study was to quantify intra-session and inter-session variability in the phasic EMG waveform patterns from the lower limb muscles during self-selected speeds of walking in healthy-normal children for comparison with adult variability in gait EMG. The variance ratio quantifies the repeatability of the integrated EMG waveform shape in a group of normally-developing children. Results reveal that between-session EMG waveform variability were similar in adult and pediatric populations, but within-session variability for the children was approximately twice the published value for adults. Clinical implications of this pediatric EMG variability suggest cautious interpretation of data from limited trial samples or inter-session changes in performance of gait data.     

Repeatability of a model for measuring multi-segment foot kinematics in children

This study used a previously tested foot model and adapted it for use with children. A number of variations on this adapted model were implemented and tested for repeatability and accuracy on 15 healthy children on three occasions. These included redefinition of the long axes of the tibia and forefoot, assessment of the flexibility of the forefoot and evaluation of the variability of the wand marker on the heel for both static and dynamic trials. It was found that variations on the model produced only minimal changes in repeatability, the only significant change being elimination of the wand marker on the heel in the static trial, which reduced between-day variability of hindfoot motion in the transverse plane. However, some differences were evident in the mean values for all variations. Based on these results, the most accurate and appropriate version of the model is proposed, and average kinematic curves are presented based on the measurements from 14 healthy children.     

Medio-lateral motion of the center of mass during obstacle crossing distinguishes elderly individuals with imbalance

This study was performed to investigate whether elderly patients with imbalance can be distinguished from healthy elderly subjects by comparing their whole body center of mass (COM) motion in the medio-lateral (M-L) direction during obstacle crossing. Nine healthy elderly adults and six elderly patients having complaints of ‘dizziness’ or ‘unsteadiness’ during walking (three with bilateral/unilateral vestibular weakness and three with unclear diagnosis) were recruited to perform unobstructed level walking and crossing of obstacles set to 2.5, 5, 10 and 15% of each subject's height. Kinematics of the COM was calculated using a weighted sum average of a 13-segment biomechanical model. There were no significant group differences for the temporal-distance gait parameters during all testing conditions. However, elderly patients with balance disorders demonstrated significantly greater and faster lateral motion of the COM when crossing over obstacles. These measurements distinguish elderly patients with imbalance from healthy elderly subjects. Furthermore, the increased M-L motion of the COM during obstacle crossing showed a positive correlation with an increased M-L range of motion of the swing foot trajectory. This increase in M-L motion indicates a compensatory adjustment in the swing foot trajectory to land the swing foot at an appropriate location that would establish a new base of support to counter the balance disturbance in the frontal plane.     

Spatio-temporal parameters and lower-limb kinematics of turning gait in typically developing children

Turning is a requirement for most locomotor tasks; however, knowledge of the biomechanical requirements of successful turning is limited. Therefore, the aims of this study were to investigate the spatio-temporal and lower-limb kinematics of 90° turning. Seventeen typically developing children, fitted with full body and multi-segment foot marker sets, having performed both step (outside leg) and spin (inside leg) turning strategies at self-selected velocity, were included in the study. Three turning phases were identified: approach, turn, and depart. Stride velocity and stride length were reduced for both turning strategies for all turning phases (p < 0.03 and p < 0.01, respectively), while stance time and stride width were increased during only select phases (p < 0.05 and p < 0.01, respectively) for both turn conditions compared to straight gait. Many spatio-temporal differences between turn conditions and phases were also found (p < 0.03). Lower-limb kinematics revealed numerous significant differences mainly in the coronal and transverse planes for the hip, knee, ankle, midfoot, and hallux between conditions (p < 0.05). The findings summarized in this study help explain how typically developing children successfully execute turns and provide greater insight into the biomechanics of turning. This knowledge may be applied to a clinical setting to help improve the management of gait disorders in pathological populations, such as children with cerebral palsy.     

Characteristics of stepping over an obstacle in community dwelling older adults under dual-task conditions

Previous research suggests that older adults may have difficulty attending to simultaneous tasks. This study was conducted to determine how concurrent performance of a secondary cognitive task influences walking and stepping over an obstacle in community dwelling older adults. Twenty-one men and women with a mean age of 73.4 years (S.D.=5.3) participated in the study. Subjects performed a gait task both alone (single-task condition) and in combination with a cognitive task that involved reciting numbers (dual-task condition). In the gait task, each subject walked at his/her fastest speed along a 10-m walkway and stepped over an obstacle designed to simulate a door threshold. Paired t-tests were used to compare gait parameters (10 m gait speed, gait speed during obstacle approach and negotiation, medial-lateral center of pressure excursion and velocity during obstacle negotiation, foot clearance over the obstacle, step length and foot position relative to the obstacle) and cognitive task performance under single and dual-task conditions. Toe-obstacle distance was greater and obstacle-heel distance was reduced under dual-task conditions. Performance of the remaining gait parameters did not change with the addition of a secondary cognitive task. Cognitive task performance decreased under dual-task conditions. These community dwelling older adults demonstrated minimal or no change in measured gait parameters during simultaneous performance of a cognitive task. The observed decrement in cognitive task performance suggests that subjects may have placed a higher priority on gait performance.     

Evaluation of a single leg stance balance test in children

Balance is a major determinate of gait. In high functioning individuals without significant vestibular or vision impairments, a ceiling effect may be present when using a double limb support protocol to assess balance function. For these populations, a single leg stance protocol may be more suitable. 47 typically developing (TD) subjects and 10 patients with CEV performed a single leg stance test on a force plate. The center of pressure (COP) was determined and several COP derived variables were calculated. Included measurements were: standard deviation, maximum excursion, area, average radial displacement, path velocity and frequency of the COP. Directional components of suitable variables were used to analyze anterior/posterior and medial/lateral contributions. Correlations with age of TD subjects indicated that all balance variables except frequency were significantly correlated. Most parameters were highly inter-correlated. Age adjusted COP balance variables also correlated to the Bruininks-Oseretsky balance subtest. Highest correlations were determined by the maximum excursion and velocity of the COP in the anterior/posterior direction. Statistical comparisons between the CEV group and a 4-6 TD group indicated significant differences between groups for most COP balance parameters. These results indicated that a single limb balance assessment may be a useful assessment for determining balance impairments in higher functioning children with orthopedic impairments.     

Reference data for performances on the standardized walking obstacle course in children developing typically

PurposeTo establish reference performance groups on the Standardized Walking Obstacle Course (SWOC) a pathway to screen ambulation for children developing typically.MethodsSWOC tests ambulation under three conditions: walk (W), walk with tray (WT) and walk wearing sunglasses (WG). One trial consisted of standing up, walking the course in one direction and sitting down. Children (n = 355) completed two trials per condition. Trial measures included time to complete (seconds) and numbers of steps, stumbles, and steps off path.ResultsTrial 1 and trial 2 for time and number of steps are significantly different (p = 0.0005), but highly correlated (r = 0.93 and r = 0.96) therefore their average was used to establish reference data. Gender was not a significant factor. Age and height predict performances in all conditions, but measures between age groups were not always significantly different. Significant different measures by height groups could be established across all conditions, therefore reference data was established using three height groups.ConclusionReference values will assist clinicians to compare a child’s performance on the SWOC based on an individual height because this can vary within and between ages thus screening for possible ambulation limitations.     

Obstacle crossing in Parkinson's disease: Mediolateral sway of the centre of mass during level-ground walking and obstacle crossing

BackgroundFalls are common in idiopathic Parkinson's disease (PD) and frequently occur when walking and crossing obstacles.ObjectiveTo determine whether people with mild to moderately severe PD have abnormal centre of mass (CoM) motion in response to the perturbations of level-ground walking and obstacle crossing.MethodMediolateral excursion and velocity of the CoM were measured using three-dimensional motion analysis and force platforms in 20 people with mild to moderately severe PD at the peak dose of their PD medication, and 20 age and sex matched healthy control participants.ResultsPeople with PD had greater sideways sway than healthy older adults when walking, particularly when walking over obstacles. People with PD also maintained their CoM more medial to their stance foot throughout the swing phase of gait compared to controls. The severity of motor symptoms in people with PD, measured using the UPDRS-III, was associated with faster sideways CoM motion but not increased CoM excursions.ConclusionsEnvironmental hazards, such as ground-based obstacles, may accentuate postural instability in people with PD. Increased mediolateral sway might be due to impaired postural responses or kinematic compensations to increase foot clearance. Fall prevention programs could benefit from inclusion of components educating people with PD about the risks associated with obstacle crossing when walking.     

Investigation of treadmill and overground running: Implications for the measurement of oxygen cost in children with developmental coordination disorder

Differences in the kinematics and kinetics of overground running have been reported between boys with and without developmental coordination disorder (DCD). This study compared the kinematics of overground and treadmill running in children with and without DCD to determine whether any differences in technique are maintained, as this may influence the outcome of laboratory treadmill studies of running economy in this population. Nine boys with DCD (10.3 ± 1.1 year) and 10 typically developing (TD) controls (9.7 ± 1 year) ran on a treadmill and overground at a matched velocity (8.8 ± 0.9 km/h). Kinematic data of the trunk and lower limb were obtained for both conditions using a 12-camera Vicon MX system. Both groups displayed an increase in stance time (p < 0.001), shorter stride length (p < 0.001), higher cadence (p < 0.001) and reduced ankle plantar flexion immediately after toe-off (p < 0.05) when running on the treadmill compared with overground. The DCD group had longer stance time (p < 0.009) and decreased knee flexion at mid-swing (p = 0.04) while running overground compared to their peers, but these differences were maintained when running on the treadmill. Treadmill running improved ankle joint symmetry in the DCD group compared with running overground (p = 0.019). Overall, these findings suggest that there are limited differences in joint kinematics and lower limb symmetry between overground and treadmill running in this population. Accordingly, laboratory studies of treadmill running in children with DCD are likely representative of the energy demands of running.     

Changes in joint kinematics and dynamic postural stability with free and restricted arm movements in children

BackgroundArm movements make a substantial and functionally relevant contribution to quiet standing and dynamic balance tasks. The impact of restricted arm movements on balance control is particularly important for children as their postural control system is not fully matured.Research questionThis study investigated the effects of arm movements on lower body joint kinematics and dynamic postural stability during anterior and lateral dynamic movements in children.MethodsEighteen boys (age, 10.1 ± 1.6 years) completed an anterior and a lateral jump-landing task under two different verbally conveyed instructions of arm position; (1) arms placed flat across the chest touching the contralateral shoulder (i.e., restricted arm movement) and (2) arm movement without restriction. Lower body joint kinematics were recorded and used to calculate mean joint position, joint range of motion (ROM) and joint movement variability.ResultsRestricting arm movements resulted in a reduction of joint movement variability and joint ROM of the pelvis during the lateral jump (p <0.05), but increased joint movement variability and joint ROM of the pelvis during the anterior jump (p <0.05).SignificanceThe reduced joint movement variability and joint ROM with restricted arm movements during the lateral jump may represent a potential compensatory ‘stiffenin strategy’, whilst the increase during the anterior jump suggest an exploratory strategy. These novel findings highlight that it is important for children to be introduced to different dynamic task constraints so that they can learn to control and organise the motor system degrees of freedom appropriately.     

Mechanical work,kinematics, and kinetics during sit-to-stand in children with and without spastic diplegic cerebral palsy

BackgroundSit-to-stand (STS) is one of the most common fundamental activity in daily life. The pathology of the neuromuscular control system in children with spastic diplegic cerebral palsy (SDCP) could contribute to atypical movement patterns leading to the inefficiency performance including the STS task. However, there was also a lack of evidence about kinematics, kinetics, and especially mechanical work during the STS task in children with SDCP aged 7–12 years old.Research questionWhat were the differences in mechanical work, kinematics and kinetics during STS task between children with SDCP and typically developing (TD) children?MethodsEleven children with SDCP (GMFCS I-II) and eleven age and gender-matched control TD children with an age range of 7–12 years were enrolled. Motion analysis and force plate systems were used to collect data. All participants performed the STS task from an adjustable chair. Independent sample t-test and two-way analysis of variance were used in this study.ResultsThe children with SDCP took a longer time and used more mechanical work during STS than TD children. At the beginning of the STS task, children with SDCP showed more trunk flexion and posterior pelvic tilting; in addition, during the STS task they also presented more trunk, hip, and knee flexion than TD children. However, the children with SDCP showed less ankle dorsiflexion compared with TD children. For the kinetic variables, asymmetry was found in children with SDCP. The maximum hip and knee extension moment, plantar flexion moment, and peak vertical ground reaction force (GRF) of the non-dominant leg were higher than the values of the dominant leg in these children.SignificanceEven though, children with SDCP who are able to independently STS. They were also a mechanically less efficient performance during STS task. Therefore, this task still needs to be trained during rehabilitation sessions.     

Anxiety-mediated gait adaptations reduce errors of obstacle negotiation among younger and older adults: implications for fall risk

The purpose of this study was to determine if anxiety-mediated gait adaptations can reduce the risk for falling among younger and older adults. Fourteen younger adults (23.14 ± 3.08 years) and 14 older adults (69.28 ± 5.41 years) participated in this study. Participants were asked to walk the length of a 7.20 m walkway and avoid contact with an obstacle that appeared suddenly underfoot at either 25% or 75% of the gait cycle duration. Testing was conducted in four conditions of postural threat. The obstacle was presented as a light beam and did not jeopardize balance when contacted. Fall risk was inferred from the frequency of obstacle contacts. Our findings indicated that obstacle contact frequency decreased when conservative gait patterns emerged. These findings imply that anxiety-mediated gait adaptations are beneficial in reducing the risk for falling among older adults and present the possibility that fear of falling may offer protective benefits for postural control. One possibility is that the beneficial effects of anxiety can only be realized among older adults who do not fear falling.     

The effects of object height and visual information on the control of obstacle crossing during locomotion in healthy older adults

In order to safely avoid obstacles, humans must rely on visual information regarding the position and shape of the object obtained in advance. The present study aimed to reveal the duration of obstacle visibility necessary for appropriate visuomotor control during obstacle avoidance in healthy older adults. Participants included 13 healthy young women (mean age: 21.5 ± 1.4 years) and 15 healthy older women (mean age: 68.5 ± 3.5 years) who were instructed to cross over an obstacle along a pressure-sensitive pathway at a self-selected pace while wearing liquid crystal shutter goggles. Participants were evaluated during three visual occlusion conditions: (i) full visibility, (ii) occlusion at T-1 step (T: time of obstacle crossing), and (iii) occlusion at T-2 steps. Toe clearances of both the lead and trail limb (LTC and TTC) were calculated. LTC in the occlusion at T-2 steps condition was significantly greater than that in other conditions. Furthermore, a significant correlation was observed between LTC and TTC in both groups, regardless of the condition or obstacle height. In the older adult group alone, step width in the occlusion at T-2 steps condition increased relative to that in full visibility conditions. The results of the present study suggest that there is no difference in the characteristics of visuomotor control for appropriate obstacle crossing based on age. However, older adults may exhibit increased dependence on visual information for postural stability; they may also need an increased step width when lacking information regarding their positional relationship to obstacles.     

The effects of improved strength on obstacle negotiation in community-living older adults

Poor mobility has been associated with age-related deterioration in muscle strength. While previous work has examined the effects of improved strength on level walking, we have quantified the effects of a resistance-training program on obstructed gait tasks using biomechanical-dependent measures. Forty-five community-dwelling participants aged 62 years or older were randomised to either a control (n=16) or experimental group (n=29). The experimental subjects exercised for 24 weeks on a progressive resistance-training program designed to improve lower body strength. Dynamic strength was assessed at weeks 0 and 24 as well as specific laboratory gait kinetics and kinematics during stepping over an obstacle and negotiation of a raised surface set at 10, 20 and 30% of each subject's leg length. Significant strength improvements (P<0.05), ranging between 197 and 285%, were recorded in the experimental group. The strength gains in the experimental group were accompanied by significant increases in obstacle-crossing stride velocity (range 5.5–15.5%) due to increases in stride length and decreases in stride duration for both gait tasks. Significant changes in the peak vertical and anterior–posterior ground reaction forces as well as in kinematic variables associated with a safe obstacle traverse such as vertical obstacle heel clearance, limb flexion at obstacle crossing, horizontal foot placement and vertical landing velocity resulted in an improved crossing strategy in the experimental subjects. These findings provide evidence of significant improvements in obstructed gait function of community-living older adults associated with a systematic resistance-training program.     

An extended index to quantify normality of gait in children

Clinical gait analysis aims to quantify and assess the mechanics of walking and identify deviations from ‘normal’ movement patterns. To facilitate the use of clinical equipment, protocols are required to process data and produce a few meaningful summary measurements which can, in turn, be used to flag gait abnormalities. Earlier work produced a one-dimensional index of gait, calculated from sagittal hip, knee and ankle rotation angle patterns. The objective of this study was to extend the original index, incorporating kinematic and kinetic data from multiple planes, while allowing for correlations between component measures. A one-dimensional index of normal gait was developed, based on normative gait data (N = 45 children, aged 3–13 years). The new one-dimensional index was calculated using correlation patterns between seven component indices, each of which has diagnostic interpretation. The effectiveness of the new index was tested using immature normative data (N = 14) and hypotonic data (N = 10). Approximately 85% of immature normative children and 100% of hypotonic children were classified as either unusual or extreme by the one-dimensional index. These data reduction protocols improve objective gait analyses in the clinical setting.     

Contribution of vision and its age-related changes to postural stability in obstacle crossing during locomotion

BackgroundObstacle crossing requires sufficient toe clearance for trip and fall prevention for which postural stability is a prerequisite. It is thought that the upper visual field plays an important role in the maintenance of postural stability, but its influence and age-dependence have not been investigated yet.Research questionWhat is the role of the visual fields in maintaining postural stability during crossing an obstacle in young and older adults?.MethodsThis study included 14 young adults and 14 older adults. The participants, wearing an accelerometer and liquid crystal shutter goggles, were asked to cross an obstacle under the following three conditions (i) full vision; (ii) total visual field occlusion at two steps before the obstacle, and (iii) lower visual field occlusion at two steps before the obstacle. The root mean square ratio in the mediolateral direction (RMSR_ML) for the three sections (i.e., approach to the obstacle, lead limb crossing, and trail limb crossing), as well as the root mean square in the mediolateral direction (RMS_ML) for each section were calculated.ResultsRMS_ML during lead limb crossing was significantly increased in older adults compared to young adults (p < 0.01). There was no significant main effect of visual condition and age group on RMSR_ML for the three steps.SignificanceThe study results suggest postural lateral instability in older adults with poor balance ability during lead limb crossing. Regardless of age, the peripheral visual information appears to contribute minimally to the maintenance of postural lateral stability at least from two steps before the obstacle, when the participants perceived the surrounding environment and the size of the obstacle while approaching it.