Obstacle Negotiation Research Articles

Stepping over an obstacle in patients with lumbar spinal stenosis: Trunk and lower extremities of kinematic and muscle activation normalized by double limb support. A preliminary study.

Patients with LSS tend to adopt a flexed lumbar posture and trunk position, particularly when stepping over an obstacle, as this activity alters the biomechanical demands placed on the trunk and lower extremities. To investigate the effects of lumbar spinal stenosis (LSS) on patients' trunk and lower-extremity kinematics, and on activities involving the gluteus medius (GMed) and vastus lateralis (VL). All participants (9 older adult patients with LSS and 11 control subjects) were required to negotiate an obstacle while walking. Trunk and lower-extremity kinematic data and GMed and VL activities were recorded using a synchronized 3D motion capture system and surface electromyography. The thoracic (12.01∘± 8.82∘ and 16.45∘± 10.80∘) and spinal (9.92∘± 14.03∘ and 5.99∘± 15.94∘) flexion angles of the leading and trailing swing limbs were higher, and the pelvic anterior tilting angle (2.37∘± 7.76∘ and 10.38∘± 8.07∘) was lower in the LSS group than in the control group (p< 0.05). With the exception of toe-off and normalized GMed activities in the contralateral leading limb (p> 0.05), all GMed (256.73 ± 112.22%, 174.00 ± 75.79%, and 270.57 ± 114.45%, respectively) and VL (208.98 ± 124.81%, 182.97 ± 93.23%, 283.91 ± 154.71%, and 394.42 ± 108.94%, respectively) activities of the contralateral leading and trailing swing limb (heel-strike and toe-off normalized activities) were significantly higher in the LSS group than in the control group (p< 0.05). Patients with LSS exhibited trunk-flexed postures when stepping over an obstacle, and these trunk alignments placed higher demands on the GMed and VL activities normalized by double-limb support during joint loading in the single-leg stance. These findings support clinical recommendations for regulating the physical activity of obstacle negotiation that may be beneficial in the management of patients with LSS.

CODESIGN E EMPODERAMENTO: A PRODUÇÃO DE JOGOS COM AS QUEBRADEIRAS DE COCO E SEUS REBENTOS EM SÃO CAETANO – MARANHÃO

This article presents the results of the development of collaboration tools between designers and an extrracivist babacu coconut community from Matinha, Maranhao that are part the outreach project called Maranhao´s conography: codesign and empowerment among designers and craftswomen and the production of images in the field. Based on the theoretical-methodological reflections of Design Anthropology, it was proposed, through the collective creation of a game, to work on abstract and theoretical questions about the parameters for the empowerment of the World Economic Forum report. The practice of collective work, as a correspondence practice has brought localized and synchronic answers to abstract issues such as economics, politics, health, and education. The production of images in the field, with the co-researchers (craftswomen and their children) brought the daily routine to the game, producing debates, creating a common space for the negotiation of problems and obstacles to empowerment and awareness of such issues.

Methods to Characterize the Real-World Use of Rollators Using Inertial Sensors–A Feasibility Study

Rollators are widely used by people with mobility problems, but previous studies have been limited to self-report approaches when evaluating their real-world effectiveness. To support studies based on more robust datasets, a method to estimate mobility parameters, such as gait speed and distance traveled, in the real world is needed. Body-worn sensors offer one approach to the problem, but rollator-mounted sensors have some practical advantages providing direct insight into patterns of walking device used, an under-researched area. We present a novel method to estimate speed and distance traveled from a single rollator-mounted IMU. The method was developed using data collected from ten rollator users performing a series of walking tasks including obstacle negotiation. The IMU data is first pre-processed to account for noise, orientation offset, and rotation-induced accelerations. The method then uses a two-stage approach. First, activity classification is used to separate the rollator data into one of three classes (movement, turning, or other). Subsequently, the speed of movement and distance traveled is estimated, using a separate estimation model for each of the three classes. The results showed high classification accuracy (precision, recall, and F1 statistics all >0.9). Speed estimation showed mean absolute errors below 0.2 m/s. Estimates for distance traveled showed errors which ranged from 5% (straight line walking) to over 70%. The results showed some promise but further work with a larger data set is needed to confirm the performance of our approach.

Stable Delay Period Representations in the Posterior Parietal Cortex Facilitate Working-Memory-Guided Obstacle Negotiation

In complex environments, information about surrounding obstacles is stored in working memory (WM) and used to coordinate appropriate movements for avoidance. In quadrupeds, this WM system is particularly important for guiding hindleg stepping, as an animal can no longer see the obstacle underneath the body following foreleg clearance. Suchobstacle WM involves the posterior parietal cortex (PPC), as deactivation of area 5 incurs WM deficits,precluding successful avoidance. However, the neural underpinnings of this involvement remain undefined. To reveal the neural substrates of this behavior, microelectrode arrays were implanted to record neuronal activity in area 5 during an obstacle WM task in cats. Early in the WM delay, neurons were modulated generally by obstacle presence or more specifically in relation to foreleg step height. Thus, information about the obstacle or about foreleg clearance can be retained in WM. In a separate set of neurons, this information was recalled later in the delay in order to plan subsequent hindleg stepping. Such early and late delay period signals were temporally bridged by neurons exhibiting obstacle-modulated activity sustained throughout the delay. These neurons represented a specialized subset of all recorded neurons, which maintained stable information coding across the WM delay. Ultimately, these various patterns of task-related modulation enable stable representations of obstacle-related information within the PPC to support successful WM-guided obstacle negotiation in the cat.

ESTABLISHING THE RELIABILITY AND VALIDITY OF THE COMPONENT TIMED-UP-AND-GO TEST TO DETERMINE BASIC PROSTHETIC MOBILITY IN PEOPLE WITH LOWER LIMB AMPUTATION

INTRODUCTION&#x0D; Studies suggest that brief bouts of activity consisting of sit-to-stand transitions, gait initiation, turning and negotiation of obstacles, are essential tasks of daily mobility, as well as prosthetic mobility1,2. Using outcome measures deemed reliable for use in the amputee population is ideal3,4. The purpose of this study was to investigate the reliability and validity of a component timed-up-and-go test (cTUG), using a mobile application (App), to evaluate basic prosthetic mobility tasks in people with lower limb amputation (LLA). The cTUG captures time required to perform the subtask components of sit to stand transitions, linear gait, and a 180˚ turn that are requisites of the standard TUG test. It was hypothesized that the cTUG would demonstrate test-retest reliability, differentiate between groups based on anatomical level of amputation, and exhibit convergent validity with other measures of prosthetic mobility and balance.&#x0D; Abstract PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/32036/24452&#x0D; How to cite: Clemens S, Gaunaurd I, Lucarevic J, Klute G, Kirk-Sanchez N, Bennett C, Gailey R. ESTABLISHING THE RELIABILITY AND VALIDITY OF THE COMPONENT TIMED-UP-AND-GO TEST TO DETERMINE BASIC PROSTHETIC MOBILITY IN PEOPLE WITH LOWER LIMB AMPUTATION. CANADIAN PROSTHETICS &amp; ORTHOTICS JOURNAL, VOLUME 1, ISSUE 2, 2018; ABSTRACT, ORAL PRESENTATION AT THE AOPA’S 101ST NATIONAL ASSEMBLY, SEPT. 26-29, VANCOUVER, CANADA, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.32036 &#x0D; Abstracts were Peer-reviewed by the AOPA 2018 National Assembly Scientific Committee.

Optimal Collision-Free Grip Planning for Biped Climbing Robots in Complex Truss Environment

Biped climbing robots (BiCRs) can overcome obstacles and perform transition easily thanks to their superior flexibility. However, to move in a complex truss environment, grips from the original point to the destination, as a sequence of anchor points along the route, are indispensable. In this paper, a grip planning method is presented for BiCRs generating optimal collision-free grip sequences, as a continuation of our previous work on global path planning. A mathematic model is firstly built up for computing the operational regions for negotiating obstacle members. Then a grip optimization model is proposed to determine the grips within each operational region for transition or for obstacle negotiation. This model ensures the total number of required climbing steps is minimized and the transition grips are with good manipulability. Lastly, the entire grip sequence satisfying the robot kinematic constraint is generated by a gait interpreter. Simulations are conducted with our self-developed biped climbing robot (Climbot), to verify the effectiveness and efficiency of the proposed methodology.

An altered spatiotemporal gait adjustment during a virtual obstacle crossing task in patients with diabetic peripheral neuropathy

This study investigates spatiotemporal gait adjustments that occur while stepping over virtual obstacles during treadmill walking in people with/without diabetic peripheral neuropathy (DPN). Eleven adults with Type 2 diabetes mellitus, ten DPN, and 11 age-matched healthy adults (HTY) participated in this study. They stepped over forthcoming virtual obstacles during treadmill walking. Outcomes such as success rate, spatiotemporal gait characteristics during obstacle crossing, and correlations between these variables were evaluated. The results partially supported our hypotheses that when comparing with HTY and DM, people with DPN adopted a crossing strategy which decreased obstacle crossing success rate and maximal toe elevation, and increased stride time and stance time during virtual obstacle crossing. This might be due to the compromised somatosensory functions of their lower extremity which may increase the risk of falling. This study also found an inter-leg relationship which may be applied to future stepping or obstacle crossing training that incorporates both legs as a means for improving outcomes of the trailing leg during daily obstacle negotiation.

Mild Cognitive Impairment Affects Obstacle Negotiation in Older Adults: Results from “Gait and Brain Study”

Background: Older adults with Mild Cognitive Impairment (MCI) are at higher risk of falls and injuries, but the underlying mechanism is poorly understood. Inappropriate anticipatory postural adjustments to overcome balance perturbations are affected by cognitive decline. However, it is unknown whether anticipatory gait control to avoid an obstacle is affected in MCI. Objective: Using the dual-task paradigm, we aim to assess whether gait control is affected during obstacle negotiation challenges in older adults with MCI. Methods: Seventy-nine participants (mean age = 72.0 ± 2.7 years; women = 30.3%) from the “Gait and Brain Study” were included in this study (controls = 27; MCI = 52). In order to assess the anticipatory control behaviour for obstacle negotiation, a 6-m electronic walkway embedded with sensors recorded foot prints to measure gait speed and step length variability, during early (3 steps before the late phase) and late (3 steps before the obstacle) pre-crossing phases of an ad hoc obstacle, set at 15% of participant’s height. Participants walked under single- and dual-task gait (counting backwards by 1’s from 100 while walking) conditions. Three-way mixed repeated-measures analysis of variance models examined differences in gait performance between groups when transitioning between pre-crossing phases towards an obstacle during single- and dual-task conditions. Analyses were adjusted for age, sex, years of education, lower limb function, fear of falling, medical status, depressive symptoms, baseline gait speed and executive function. Results: A significant three-way interaction among groups, pre-crossing phases and task showed that participants with MCI attenuated the gait deceleration (p = 0.02) and performed fewer step length adjustments (p = 0.03) when approaching the obstacle compared with controls while dual-tasking. These interactions were attenuated when executive function performance was added as a covariate in the adjusted statistical model. Conclusion: Older adults with MCI attenuate the anticipatory gait adjustments needed to avoid an obstacle when dual-tasking. Deficits in higher-order cognitive processing may limit obstacle negotiation capabilities in MCI populations, being a potential falls risk factor.

Decomposing sensorimotor variability changes in ageing and their connection to falls in older people

The relationship between sensorimotor variability and falls in older people has not been well investigated. We developed a novel task having shared biomechanics of obstacle negotiation to quantify sensorimotor variability related to locomotion across age. We found that sensorimotor variability in foot placement increases continuously with age. We then applied sensory psychophysics to pinpoint the visual and somatosensory systems associated with sensorimotor variability. We showed increased sensory variability, specifically increased proprioceptive variability, the vital cause of more variable foot placement in older people (greater than 65 years). Notably, older participants relied more on the vision to judge their own foot’s height compared to the young, suggesting a shift in multisensory integration strategy to compensate for degenerated proprioception. We further modelled the probability of tripping-over based on the relationship between sensorimotor variability and age and found a correspondence between model prediction and community-based data. We reveal increased sensorimotor variability, modulated by sensation precision, a potentially vital mechanism of raised tripping-over and thus fall events in older people. Analysis of sensorimotor variability and its specific components may have the utility of fall risk and rehabilitation target evaluation.

Kinematic patterns for hindlimb obstacle avoidance during sheep locomotion

ABSTRACTFunctional recovery following general nerve reconstruction is often associated with poor results. Comparing to rat and mice experimental studies, there are much fewer investigations on nerve regeneration and repair in the sheep, and there are no studies on this subject using gait analysis in the sheep model as an assessment tool. Additionally, this is the first study evaluating obstacle negotiation and the compensatory strategies that take place at each joint in response to the obstacle during locomotion in the sheep model. This study aims to get kinematic data to serve as a template for an objective assessment of the ankle joint motion in future studies of common peroneal nerve (CP) injury and repair in the ovine model. Our results show that a moderately high obstacle set to 10% of the sheep’s hindlimb length was associated to several spatial and temporal strategies in order to increase hoof height during obstacle negotiating. Sheep efficiently cleared an obstacle by increasing knee, ankle and metatarsophalangeal flexion during swing, whereas the hip joint is not affected. This study establishes the bounds of normal motion in the neurologically intact hindlimb when approached and cleared an obstacle and provides baseline data for further studies of peripheral nerve research in the ovine model.

Effects of obesity and knee osteoarthritis on gait and postural stability in pre-bariatric surgery candidates

Knee osteoarthritis (OA) is the most common cause of chronic disability and is frequently comorbid with obesity. The personal burden of knee OA and obesity are substantial. Adults with knee OA with obesity demonstrate postural instability, which makes them susceptible to falls. The purpose of this study was to investigate gait and postural stability during flat ground walking and obstacle crossing in pre-bariatric surgery candidates. Forty-four adults with obesity (mean BMI = 43.35, SD = 4.33) and 30 adults without obesity (mean BMI = 23.10, SD–3.98) walked 60 feet at self-selected paces for 25 trials under five conditions: initial baseline on flat ground, crossing low (4 cm), medium (11 cm), and high (16 cm) obstacles, and final baseline on flat ground. Spatiotemporal kinematics were collected with a gait carpet (Protokinetics). During the final baseline, for adults with obesity, most parameters improved ( P s < 0.05); at the final baseline condition, participants had the fastest step times, stance times, single limb support times, and velocities. The analyses also revealed that during obstacle negotiation, participants had longer step times, slower velocity and wider step widths compared to level ground walking ( P s < 0.05). Most alterations in gait for individuals with obesity were observed during high obstacle crossing ( P s < 0.05). The findings suggest that obstacles pose a challenge beyond flat ground walking for pre-bariatric surgery candidates. Obstacle height also influenced participants’ gait. This supports the utility of examining gait in this population during tasks beyond flat ground walking.

A dynamic model of unsupported pit traversal by a vehicle with 6×6 wheel arrangement

The paper deals with the problem of unsupported pit traversal by a vehicle with 6×6 wheel arrangement. The paper contains passages from an unsupported pit traversal test report of “Korsak” wheel chassis. Typical test episodes are described. A design schematic is provided. Assumptions are provided. For the first time, a mathematical model is provided describing a dynamical pit traversal under recognition of the soil parameters, mass and inertia chassis specifications, as well as the travel speed. A conclusion is made that the obtained model is a more generalized case of existing models describing profile obstacle negotiation by wheel vehicles.

Walking combined with reach-to-grasp while crossing obstacles at different distances

BackgroundObstacle avoidance and object prehension occur regularly in real-world environments (walking up/down steps and opening a door). However, it is not known how walking and prehension change when there is an increase in the level of difficulty of the walking task. Research questionWe investigated the changes in walking and reach-tograsp when performing these two motor skills concomitantly in the presence of an obstacle on the ground positioned in different locations in relation to the object-to-be-grasped. MethodsFifteen young adults walked and grasped a dowel placed on a support with the obstacle positioned at the step before (N-1), during (N) and after (N + 1) the prehension task. ResultsThe prehension task did not affect leading limb obstacle negotiation. Toe clearance and maximum toe elevation were lesser at obstacle position N + 1 than at obstacle position N-1 when combining grasping and obstacle-crossing task for the trailing limb. Step width increased in the presence of the obstacle-crossing task independent of obstacle location. The correlation between foot position before the obstacle and toe clearance revealed that the addition of the prehension task disrupted the relationship between these variables for the trailing limb. Foot placement and limb elevation were unaffected by the prehension task. The reaching component was unaffected by the increased level of difficulty of the walking task. The grasping component was affected by the increased level of difficulty of the walking task, as the time to peak grip aperture occurred earlier in the presence of the obstacle at position N, and may indicate a cautious strategy to grasp the dowel successfully. SignificanceOur results showed that prospective control is affected after the prehension since the attention to grasping may have impaired the acquisition of visual information for planning the trailing limb elevation.

Effects of Aging on the Obstacle Negotiation Strategy while Stepping over Multiple Obstacles

Forty-seven percent of falling accidents in older adults are caused by tripping over obstacles. Understanding what strategies are involved in obstacle negotiation in older adults could reduce fall risks. There is a paucity of research investigating how healthy adults negotiate multiple obstacles, which may better reflect the complexity of the real environment. The presence of a second obstacle has induced mixed results in the obstacle negotiation of healthy older adults with the interval between obstacles two steps apart. This study extended the knowledge to understand what strategies healthy younger and older adults used to step over two obstacles placed at three-step-length apart. Twenty healthy subjects performed 2 tasks: level ground walking and stepping over two obstacles. The height of each obstacle was set at 10% of subjects’ leg height. We found that aging significantly increased the toe clearance in leading and trailing legs when stepping over the obstacles at a three-step-length interval. Toe clearance was higher while stepping over the second obstacle than the first one in older adults. These results had two-fold meanings: the three-step-length interval was long enough to trigger the adjustment of the obstacle negotiation strategy, and aging led older adults to use conservative negotiation strategies.

Mechanism Design and Kinematic Analysis of a Novel Inspection Robot with Four Arms

To meet the requirements of mechanical dimensions, climbing performance and obstacle negotiation capability of an inspection robot on the long-span transmission line, a novel inspection robot with four arms is designed by drawing on the research on human being’s climbing on a tree. Firstly, according to its kinematical characteristics we learned from human being’s tree climbing, the mechanism configuration of the robot on the transmission line is introduced and methods of overcoming two typical obstacles are planned. Then, its main structural parameters are provided, its kinematics equation is derived, and the analysis of kinematics performances such as grade ability and obstacle overcoming is carried out to verify the feasibility of the mechanism design. Finally, experiments on movement are conducted on the platform of virtual prototype. The results indicate that the robot has such features as excellent grade ability and obstacle overcoming performance.

The quality of visual information about the lower extremities influences visuomotor coordination during virtual obstacle negotiation.

Successful negotiation of obstacles during walking relies on the integration of visual information about the environment with ongoing locomotor commands. When information about the body and the environment is removed through occlusion of the lower visual field, individuals increase downward head pitch angle, reduce foot placement precision, and increase safety margins during crossing. However, whether these effects are mediated by loss of visual information about the lower extremities, the obstacle, or both remains to be seen. Here we used a fully immersive, virtual obstacle negotiation task to investigate how visual information about the lower extremities is integrated with information about the environment to facilitate skillful obstacle negotiation. Participants stepped over virtual obstacles while walking on a treadmill with one of three types of visual feedback about the lower extremities: no feedback, end-point feedback, and a link-segment model. We found that absence of visual information about the lower extremities led to an increase in the variability of leading foot placement after crossing. The presence of a visual representation of the lower extremities promoted greater downward head pitch angle during the approach to and subsequent crossing of an obstacle. In addition, having greater downward head pitch was associated with closer placement of the trailing foot to the obstacle, further placement of the leading foot after the obstacle, and higher trailing foot clearance. These results demonstrate that the fidelity of visual information about the lower extremities influences both feedforward and feedback aspects of visuomotor coordination during obstacle negotiation. NEW & NOTEWORTHY Here we demonstrate that visual information about the lower extremities is utilized for precise foot placement and control of safety margins during obstacle negotiation. We also found that when a visual representation of the lower extremities is present, this information is used in the online control of foot trajectory. Together, our results highlight how visual information about the body and the environment is integrated with motor commands for planning and online control of obstacle negotiation.

Accuracy of Activity Trackers in Parkinson Disease: Should We Prescribe Them?

Wearable, consumer-grade activity trackers have become widely available as a means of monitoring physical activity in the form of step counts. However, step counts may not be accurate in persons with Parkinson disease (PD) due to atypical gait characteristics. This study aimed to investigate the accuracy of 4 consumer-grade activity trackers in individuals with PD while ambulating during continuous and discontinuous walking tasks. This study used a cross-sectional design. Thirty-three persons with PD (Hoehn & Yahr stages 1-3) donned 4 models of activity trackers on the less affected side of their bodies. Participants performed 2 continuous walking tasks (2-minute walk tests at comfortable and fast speeds) and 2 discontinuous walking tasks (a simulated household course and an obstacle negotiation course) in an outpatient setting. Bland-Altman plots and intraclass correlation coefficients [ICC(2,1)] were computed as a measure of agreement between actual steps taken (reference standard: video recording) and steps recorded by each tracker. The accuracy of the activity trackers varied widely, with ICCs ranging from -0.03 to 0.98. Overall, the most accurate device across all tasks was the Fitbit Zip, and the least accurate was the Jawbone Up Move during the simulated household course. All activity trackers were more accurate for continuous walking tasks compared with discontinuous walking tasks. Waist-mounted devices were more accurate than wrist-mounted devices with continuous tasks. Bland-Altman plots revealed that all activity trackers underestimated step counts. All walking tasks were measured over relatively short distances. In persons with mild-to-moderate PD, waist-worn activity trackers may be prescribed to monitor bouts of continuous walking with reasonable accuracy; however, activity trackers have little utility in monitoring discontinuous walking common in household settings.

Analysis of Engineer Obstacle Negotiation Possibility with Grouping Robots

Analysis of Engineer Obstacle Negotiation Possibility with Grouping Robots

Dynamic balance during walking adaptability tasks in individuals post-stroke

Maintaining dynamic balance during community ambulation is a major challenge post-stroke. Community ambulation requires performance of steady-state level walking as well as tasks that require walking adaptability. Prior studies on balance control post-stroke have mainly focused on steady-state walking, but walking adaptability tasks have received little attention. The purpose of this study was to quantify and compare dynamic balance requirements during common walking adaptability tasks post-stroke and in healthy adults and identify differences in underlying mechanisms used for maintaining dynamic balance. Kinematic data were collected from fifteen individuals with post-stroke hemiparesis during steady-state forward and backward walking, obstacle negotiation, and step-up tasks. In addition, data from ten healthy adults provided the basis for comparison. Dynamic balance was quantified using the peak-to-peak range of whole-body angular-momentum in each anatomical plane during the paretic, nonparetic and healthy control single-leg-stance phase of the gait cycle. To understand differences in some of the key underlying mechanisms for maintaining dynamic balance, foot placement and plantarflexor muscle activation were examined. Individuals post-stroke had significant dynamic balance deficits in the frontal plane across most tasks, particularly during the paretic single-leg-stance. Frontal plane balance deficits were associated with wider paretic foot placement, elevated body center-of-mass, and lower soleus activity. Further, the obstacle negotiation task imposed a higher balance requirement, particularly during the trailing leg single-stance. Thus, improving paretic foot placement and ankle plantarflexor activity, particularly during obstacle negotiation, may be important rehabilitation targets to enhance dynamic balance during post-stroke community ambulation.

Evidence for Differential Effects of 2 Forms of Exercise on Prefrontal Plasticity During Walking in Parkinson’s Disease

Background. In a randomized control trial conducted in patients with Parkinson’s disease, a treadmill training program combined with virtual reality that targeted motor and cognitive aspects of safe ambulation led to fewer falls, compared with treadmill training alone. Objective. To investigate if the 2 types of training differentially affected prefrontal activation and if this might explain differences in fall rates after the intervention. Methods. Sixty-four patients with Parkinson’s disease were randomized into the treadmill training arm (n = 34, mean age 73.1 ± 1.1 years, 64% men, disease duration 9.7 ± 1.0 years) or treadmill training with virtual reality arm (n = 30, mean age 70.1 ± 1.3 years, 71% men, disease duration 8.9 ± 1.1 years). Prefrontal activation during usual, dual-task, and obstacle negotiation walking was assessed before and after 6 weeks of training, using a functional near-infrared spectroscopy system. Results. Treadmill training with and without virtual reality reduced prefrontal activation during walking (P < .001), with specific interactions related to training arm (P = .01), lateralization (P = .05), and walking condition (P = .001). For example, among the subjects who trained with treadmill training alone, prefrontal activation during dual-task walking and obstacle negotiation increased after training, while in the combined training arm, activation decreased. Conclusions. Prefrontal activation during usual and during more challenging walking conditions can be altered in response to 2 different types of training. The addition of a cognitive training component to a treadmill exercise program apparently modifies the effects of the training on the magnitude and lateralization of prefrontal activation and on falls, extending the understanding of the plasticity of the brain in PD.