Obstacle Negotiation Research Articles

Prefrontal cortex activation during obstacle negotiation: What’s the effect size and timing?

BackgroundObstacle negotiation is a daily activity that requires the integration of sensorimotor and cognitive information. Recent studies provide evidence for the important role of prefrontal cortex during obstacle negotiation. We aimed to explore the effects of obstacle height and available response time on prefrontal activation. MethodsTwenty healthy young adults (age: 30.1 ± 1.0 years; 50% women) walked in an obstacle course while negotiating anticipated and unanticipated obstacles at heights of 50 mm and 100 mm. Prefrontal activation was measured using a functional near-infrared spectroscopy system. Kinect cameras measured the obstacle negotiation strategy. Prefrontal activation was defined based on mean level of HbO2 before, during and after obstacle negotiation and the HbO2 slope from gait initiation and throughout the task. Changes between types of obstacles were assessed using linear-mix models and partial correlation analyses evaluated the relationship between prefrontal activation and the distance between the feet as the subjects traversed the obstacles. ResultsDifferent obstacle heights showed similar changes in prefrontal activation measures (p > 0.210). However, during unanticipated obstacles, the slope of the HbO2 response was steeper (p = 0.048), as compared to anticipated obstacles. These changes in prefrontal activation during negotiation of unanticipated obstacles were correlated with greater distance of the leading foot after the obstacles (r = 0.831, p = 0.041). ConclusionsThese findings are the first to show that the pattern of prefrontal activation depends on the nature of the obstacle. More specifically, during unanticipated obstacles the recruitment of the prefrontal cortex is faster and greater than during negotiating anticipated obstacles. These results provide evidence of the important role of the prefrontal cortex and the ability of healthy young adults to tailor the activation pattern to different types of obstacles.

Motion Planning for Bipedal Robot to Perform Jump Maneuver

The remarkable ability of humans to perform jump maneuvers greatly contributes to the improvements of the obstacle negotiation ability of humans. The paper proposes a jumping control scheme for a bipedal robot to perform a high jump. The half-body of the robot is modeled as three planar links and the motion during the launching phase is taken into account. A geometrically simple motion was first conducted through which the gear reduction ratio that matches the maximum motor output for high jumping was selected. Then, the following strategies to further exploit the motor output performance was examined: (1) to set the maximum torque of each joint as the baseline that is explicitly modeled as a piecewise linear function dependent on the joint angular velocity; (2) to exert it with a correction of the joint angular accelerations in order to satisfy some balancing criteria during the motion. The criteria include the location of ZMP (zero moment point) and the torque limit. Using the technique described above, the jumping pattern is pre-calculated to maximize the jump height. Finally, the effectiveness of the proposed method is evaluated through simulations. In the simulation, the bipedal robot model achieved a 0.477-m high jump.

Forelimb position affects facultative bipedal locomotion in lizards.

Recent work indicates that bipedal posture in lizards is advantageous during obstacle negotiation. However, little is known about how bipedalism occurs beyond a lizard's acceleratory threshold. Furthermore, no study to date has examined the effects of forelimb position on the body center of mass (BCoM) in the context of bipedalism. This study quantified the frequency of bipedalism when sprinting with versus without an obstacle at 0.8 m from the start of a sprint. Forelimb positions were quantified during bipedal running at the start of a sprint and when crossing an obstacle. Two species with contrasting body forms (and thus different BCoM) were studied (Sceloporus woodi and Aspidoscelis sexlineata) to assess potential variation due to body plan and obstacle-crossing behavior. No significant difference in frequency of bipedalism was observed in S. woodi with or without an obstacle. However, A. sexlineata primarily used a bipedal posture when sprinting. Forelimb positions were variable in S. woodi and stereotyped in A. sexlineata Caudal extension of the forelimbs helped shift the BCoM posteriorly and transition to, or maintain, a bipedal posture in A. sexlineata, but not in S. woodi The posterior shift in BCoM, aided by more caudally placed forelimbs, helps raise the trunk from the ground, regardless of obstacle presence. The body plan, specifically the length of the trunk and tail, and forelimb position work together with acceleration to shift the BCoM posteriorly to transition to a bipedal posture. Thus, species exhibit morphological and behavioral adjustments to transition to and maintain facultative bipedalism while sprinting.

Reliability of center of pressure measures of gait initiation time in healthy older adults: Effect of obstacle negotiation and cognitive load on reaction and anticipatory postural adjustment phases

Reliability of center of pressure measures of gait initiation time in healthy older adults: Effect of obstacle negotiation and cognitive load on reaction and anticipatory postural adjustment phases

Retraining walking adaptability following incomplete spinal cord injury

IntroductionFunctional walking requires the ability to modify one’s gait pattern to environmental demands and task goals—gait adaptability. Following incomplete spinal cord injury (ISCI), gait rehabilitation such as locomotor training (Basic-LT) emphasizes intense, repetitive stepping practice. Rehabilitation approaches focusing on practice of gait adaptability tasks have not been established for individuals with ISCIs but may promote recovery of higher level walking skills. The primary purpose of this case series was to describe and determine the feasibility of administering a gait adaptability retraining approach—Adapt-LT—by comparing the dose and intensity of Adapt-LT to Basic-LT.Case presentationThree individuals with ISCIs (>1 year, AIS C or D) completed three weeks each (15 sessions) of Basic-LT and Adapt-LT. Interventions included practice on a treadmill with body weight support and practice overground (≥30 mins total). Adapt-LT focused on speed changes, obstacle negotiation, and backward walking. Training parameters (step counts, speeds, perceived exertion) were compared and outcomes assessed pre and post interventions. Based on completion of the protocol and similarities in training parameters in the two interventions, it was feasible to administer Adapt-LT with a similar dosage and intensity as Basic-LT. Additionally, the participants demonstrated gains in walking function and balance following each training type.DiscussionRehabilitation that includes stepping practice with adaptability tasks is feasible for individuals with ISCIs. Further investigation is needed to determine the efficacy of Adapt-LT.

Different protocols for analyzing behavior and adaptability in obstacle crossing in Parkinson's disease.

Imbalance and tripping over obstacles as a result of altered gait in older adults, especially in patients with Parkinson’s disease (PD), are one of the most common causes of falls. During obstacle crossing, patients with PD modify their behavior in order to decrease the mechanical demands and enhance dynamic stability. Various descriptions of dynamic traits of gait that have been collected over longer periods, probably better synthesize the underlying structure and pattern of fluctuations in gait and can be more sensitive markers of aging or early neurological dysfunction and increased risk of falls. This confirmation challenges the clinimetric of different protocols and paradigms used for gait analysis up till now, in particular when analyzing obstacle crossing. The authors here present a critical review of current knowledge concerning the interplay between the cognition and gait in aging and PD, emphasizing the differences in gait behavior and adaptability while walking over different and challenging obstacle paradigms, and the implications of obstacle negotiation as a predictor of falls. Some evidence concerning the effectiveness of future rehabilitation protocols on reviving obstacle crossing behavior by trial and error relearning, taking advantage of dual-task paradigms, physical exercise, and virtual reality have been put forward in this article.

Age-associated changes in obstacle negotiation strategies: Does size and timing matter?

IntroductionTripping over an obstacle is one of the most common causes of falls among older adults. However, the effects of aging, obstacle height and anticipation time on negotiation strategies have not been systematically evaluated. MethodsTwenty older adults (ages: 77.7±3.4years; 50% women) and twenty young adults (age: 29.3±3.8years; 50% women) walked through an obstacle course while negotiating anticipated and unanticipated obstacles at heights of 25mm and 75mm. Kinect cameras captured the: (1) distance of the subject’s trailing foot before the obstacles, (2) distance of the leading foot after the obstacles, (3) clearance of the leading foot above the obstacles, and (4) clearance of the trailing foot above the obstacles. Linear-mix models assessed changes between groups and conditions. ResultsOlder adults placed their leading foot closer to the obstacle after landing, compared to young adults (p<0.001). This pattern was enhanced in high obstacles (group*height interaction, p=0.033). Older adults had lower clearance over the obstacles, compared to young adults (p=0.007). This was more pronounced during unanticipated obstacles (group*ART interaction, p=0.003). The distance of the leading foot and clearance of the trailing foot after the obstacles were correlated with motor, cognitive, and functional abilities. ConclusionsThese findings suggest that there are age-related changes in obstacle crossing strategies that are dependent on the specific characteristics of the obstacle. The results have important implications for clinical practice, suggesting that functional exercise should include obstacle negotiation training with variable practice of height and available response times. Further studies are needed to better understand the effects of motor and cognitive abilities.

Obstacle negotiation attempts by leaping cyprinids indicate bank-side spawning migration routes

Understanding freshwater fish population ecology is a pre-requisite for their conservation, management, and exploitation. Many populations of cyprinids, the largest family of freshwater fish, undertake potamodromous migrations. This has important implications for the conservation and management of their stocks. Habitat and connectivity loss are the main factors threatening these stocks. The fine-scale routes (i.e., banks vs. midchannel) of cyprinid spawning migrations in generally turbid rivers are largely unknown, contrary to other taxa such as salmonids, shads, and eels. In this work, we studied the fine-scale leaping behavior of two cyprinid taxa (Luciobarbus sp., barbels) which support commercial and recreational fisheries. We used fish size and leap distance to the margin as indicative of fine-scale spawning migration routes following the river banks vs. midchannel. The results support the idea that these cyprinids migrate close to the banks, and that the larger adults migrate nearer the banks than the smaller ones. This marks a difference between cyprinids and salmonids, showing that knowledge of cyprinid migration routes can help fisheries managers develop improved, more permeable, barriers and less selective fish pass facilities. Particularly, this behavior of cyprinid species can be applied to optimize the design of fish pass facilities: first, by installing fish passes on each bank of wide rivers, where the large lateral distance may make a single facility difficult to find; and second, by using either a single wider entrance or several narrower entrances distributed over a greater distance from the margins so as to cover the more distant stretch used by the younger adults.

Neural correlates of obstacle negotiation in older adults: An fNIRS study

Older adults are less efficient at avoiding obstacles compared to young adults, especially under attention-demanding conditions. Using functional near-infrared-spectroscopy (fNIRS), recent studies implicated the prefrontal cortex (PFC) in cognitive control of locomotion, notably under dual-task walking conditions. The neural substrates underlying Obstacle Negotiation (ON), however, have not been established. The current study determined the role of the PFC in ON during walking in seniors. Non-demented older adults (n=90; mean age=78.1±5.5years; %female=51) underwent fNIRS acquisition to assess changes in hemodynamic activity in the PFC during normal-walk [NW] and walk-while-talk [WWT] conditions with and without obstacles. Obstacles were presented as red elliptical shapes using advanced laser technology, which resemble potholes. Linear mixed effects models were used to determine differences in oxygenated hemoglobin (HbO2) levels among the four task conditions. The presence of slow gait, a risk factor for dementia and falls, served as a predictor hypothesized to moderate the effect of obstacles on PFC HbO2 levels. PFC HbO2 levels were significantly higher in WWT compared to NW (p<0.001) irrespective of ON. Slow gait moderated the effect of obstacles on HbO2 levels across task conditions. Specifically, compared to participants with normal gait, PFC HbO2 levels were significantly increased in ON-NW relative to NW (p=0.017) and ON-WWT relative to WWT (p<0.001) among individuals with slow gait. Consistent with Compensatory Reallocation, ON required greater PFC involvement among individuals with mobility limitations.

Manipulating the fidelity of lower extremity visual feedback to identify obstacle negotiation strategies in immersive virtual reality.

The ability to successfully navigate obstacles in our environment requires integration of visual information about the environment with estimates of our body's state. Previous studies have used partial occlusion of the visual field to explore how information about the body and impending obstacles are integrated to mediate a successful clearance strategy. However, because these manipulations often remove information about both the body and obstacle, it remains to be seen how information about the lower extremities alone is utilized during obstacle crossing. Here, we used an immersive virtual reality (VR) interface to explore how visual feedback of the lower extremities influences obstacle crossing performance. Participants wore a head-mounted display while walking on treadmill and were instructed to step over obstacles in a virtual corridor in four different feedback trials. The trials involved: (1) No visual feedback of the lower extremities, (2) an endpoint-only model, (3) a link-segment model, and (4) a volumetric multi-segment model. We found that the volumetric model improved success rate, placed their trailing foot before crossing and leading foot after crossing more consistently, and placed their leading foot closer to the obstacle after crossing compared to no model. This knowledge is critical for the design of obstacle negotiation tasks in immersive virtual environments as it may provide information about the fidelity necessary to reproduce ecologically valid practice environments.

TREADMILL TRAINING WITH VIRTUAL REALITY TO REDUCE FALLS AMONG OLDER ADULTS: RCT RESULTS

A randomized, controlled trial tested the hypothesis that a combined treadmill training with virtual reality (TT+VR) intervention would lead to fewer falls, compared to treadmill training alone (TT). 302 community-living older adults (age: 73.8 ± 6.7 yrs; 60.3% women) with a history of multiple falls and a range of motor and cognitive deficits were randomly assigned to six weeks of TT+VR or TT. The primary outcome was the falls incident rate (IR) during the 6 months post-training. Before training, the IR was similar in both training arms (p=0.29). Following training, the IR was 42% lower (p=0.033) in TT+VR, compared to TT (IRR:0.58; 95%CI:0.36–0.96). Post training, gait variability during obstacle negotiation, physical performance-based measures, and health-related QOL were significantly better in TT+VR post-training, compared to TT. An integrated, multi-modal approach targeting relevant motor and cognitive functions led to lower fall rates than treadmill training alone, with added benefits to mobility and QOL.

Impact of age and obstacle negotiation on timing measures of gait initiation

IntroductionThe separate and combined impacts of age and walkway obstruction on reaction time, anticipatory postural adjustment phases of gait initiation and cognitive dual task performance are not well understood. This study aimed to a) examine the impact of age and task complexity on reaction and anticipatory postural adjustment phases separately b) examine the impact of age and walkway obstruction on cognitive task performance while walking. MethodNineteen older adults (mean age± SD: 66.73 ± 3.38 years) and twelve younger adults (mean age± SD: 26.5 ± 4.37 years), participated in this study. The tests were performed in four conditions: a smooth walkway; a smooth walkway with concurrent cognitive task; an obstructed walkway; and an obstructed walkway with a concurrent cognitive task. Reaction and anticipatory postural adjustment phases were measured from the recorded center of pressure trajectory data. ResultsReaction time phase was significantly longer in the older group (P = 0.04), but there was no significant impact of task complexity (P = 0.95). Conversely, there was a significant impact of task complexity on anticipatory postural adjustment phase (P = 0.04), but there was no significant difference between the age groups (P = 0.38). Cognitive task response time was not significantly different between age groups or with walkway obstruction (P = 0.19 and P = 0.90 respectively).There were no significant interactions between age group and task complexity. ConclusionReaction time phase but not anticipatory postural adjustment phase was longer in healthy older than younger adults. Anticipatory postural adjustment phase but not reaction time phase was slower for more complex gait initiation tasks. Cognitive task performance was similar across age groups and conditions.

Physical Fitness Predictors Of A Warrior Task Simulation Test

Modern warfare requires full-spectrum physical fitness to achieve combat effectiveness, resiliency, and survivability on the battlefield. Determining which physical fitness components are essential to performing well in a Warrior Task Simulation Test (WTST) can contribute toward a better understanding on how best to test and train military physical performance. Currently, there are limited studies that have examined the relationship between WTST performance and the physical fitness components. PURPOSE: To identify the underlying and modifiable components of physical fitness related to WTST performance. METHODS: Forty-three healthy and physically active men (age: 22 ± 3 yrs; height: 178 ± 8 cm; mass: 78 ± 11 kg) participated in one WTST session and one laboratory test session. The WTST was a continuous 9 sequential-event course comprised of running, jumping, crawling, climbing, obstacle negotiation, and material handling tasks. Physical fitness measurements in the laboratory test sessions included muscular strength and endurance, postural stability, aerobic capacity, anaerobic capacity, flexibility, body composition, fat-free mass, and agility. Backward stepwise multiple linear regression analysis was performed to predict time to completion of the WTST using the physical fitness measurements. RESULTS: Average time to completion of the WTST was 238.6 ± 31.1 seconds. (a) Muscular endurance, (b) aerobic capacity, (c) body composition, (d) fat-free mass, and (e) agility significantly contributed to a model that predicted time to completion of the WTST (R2 = 51.78, p < 0.001). The regression equation was: time to completion of the WTST = 250.21 – 0.02 * (a) – 1.34 * (b) + 0.81 * (c) – 0.77 * (d) + 24.12 * (e). CONCLUSION: The WTST assesses a combination of modifiable physical fitness components consisting of muscular endurance, aerobic capacity, body composition, fat-free mass, and agility, which suggest that skill-related components of physical fitness such as agility need to be measured and tracked in addition to health-related ones in order to gain better insight to Soldiers’ ability to accomplish their mission successfully. Supported by Freddie H. Fu, MD Graduate Research Award, SHRS Research Development Fund

Investigation on Semi-active Suspension System for Multi-axle Armoured Vehicle using Co-simulation

&lt;p&gt;The objective of the study is to evaluate the performance of various semi-active suspension control strategies for 8x8 multi-axle armoured vehicles in terms of comparative analysis of ride quality and mobility parameters during negotiation of typical military obstacles. Since the cost, complexity and time precludes realisation of actual system, co-simulation technique has been effectively implemented for this investigation. Co-simulation combines advanced virtual prototyping and control technology which offers a novel approach to investigate the dynamics of such complex system. The simulations for the integrated control system along with multi body model of the vehicle are carried out for the control strategies, viz. continuous sky hook control, cascade loop control and cascade loop with ride control and compared with passive suspension system. The vehicle with 8x8 configuration is run on the real world obstacle profiles, viz. step, trench, trapezoidal bump and corrugated road and the effect of control strategies on ride comfort, wheel displacement and ground reaction is presented. It is observed that cascade loop with ride control in semi-active mode offers better vehicle ride comfort while crossing the said obstacles. The improved performance parameters are achieved through stabilisation of heave, pitch and roll motions of the vehicle through outer loop and isolation of vehicle level uneven disturbances through the fuzzy logic controller employed in inner loop.&lt;/p&gt;

Effects of aging on prefrontal brain activation during challenging walking conditions

BackgroundDeficits in cognitive domains, in particular, those related to the prefrontal cortex, contribute to diminished walking performance in complex conditions in older age. Studies using functional near infra-red spectroscopy (fNIRS) reported inconsistent findings of brain activation age-related changes in response to increased task demands. We aimed to study the effects of aging on gait and prefrontal activation in complex walking tasks with internal and external task demands. MethodsTwenty-three healthy young adults (30.9±3.7yrs) and 20 healthy older adults (69.7±5.8yrs) participated in this study. Gait and prefrontal activation were assessed during three walking conditions: (1) usual walking, (2) dual tasking (internal task demands) and, (3) obstacle negotiation (external task demands). fNIRS measured changes in oxygenated hemoglobin concentrations in the prefrontal cortex. ResultsSeveral gait measures were worse in older compared to younger adults under all walking conditions (p<0.005). Even at the lowest level of challenge, older adults had significant increases in HbO2 levels during usual walking, relative to standing (p=0.006). Both groups showed increased activation during dual-task (p<0.002) and during obstacle negotiation (p<0.003). ConclusionsPrefrontal activation during walking is dependent on age and task properties and that older adults apparently rely more on cognitive resources even during usual walking task.

Going Up or Sideways? Perception of Space and Obstacles Negotiating by Cuttlefish.

While octopuses are mostly benthic animals, and squid prefer the open waters, cuttlefish present a special intermediate stage. Although their body structure resembles that of a squid, in many cases their behavior is mostly benthic. To test cuttlefish's preference in the use of space, we trained juvenile Sepia gibba and Sepia officinalis cuttlefish to reach a shelter at the opposite side of a tank. Afterwards, rock barriers were placed between the starting point and the shelter. In one experiment, direct paths were available both through the sand and over the rocks. In a second experiment the direct path was blocked by small rocks requiring a short detour to by-pass. In the third experiment instead, the only direct path available was over the rocks; or else to reach the goal via an exclusively horizontal path a longer detour would have to be selected. We showed that cuttlefish prefer to move horizontally when a direct route or a short detour path is available close to the ground; however when faced with significant obstacles they can and would preferentially choose a more direct path requiring a vertical movement over a longer exclusively horizontal path. Therefore, cuttlefish appear to be predominantly benthic dwellers that prefer to stay near the bottom. Nonetheless, they do view and utilize the vertical space in their daily movements where it plays a role in night foraging, obstacles negotiation and movement in their home-range.

Kinematics of the Pelvis, Torso, and Lower Limb During Obstacle Negotiation While Under Temporal Constraints.

Biomechanics of unobstructed locomotion consists of synchronized complex movements of the pelvis, torso, and lower limbs. These movement patterns become more complex as individuals encounter obstacles or negotiate uneven terrain. To date, limited research has explored how specifically the pelvis, torso, and lower limb segments relate to obstacle negotiation of varying sized objects combined with temporal constraints to perform the task. Understanding pelvis and adjoining segment movements during object negotiation will provide necessary information in identifying abnormal mechanics and potential fall risk characteristics in balance compromised patient populations. In this prospective cohort study, we aimed to compare pelvic, torso, and lower limb kinematics during unobstructed locomotion with obstacle negotiation of varying heights. Ten healthy young adults (7 females and 3 males, mean age 28.4 ± 4.1 years, mean body mass index 22.5 ± 3.6 kg/m2 ) enrolled in this study. Analysis of within-subject differences revealed a significant increase in sagittal (posterior tilt) and frontal (ipsilateral hike) plane pelvic angular displacement and higher sagittal plane posterior torso lean angular displacement with increased obstacle height. Furthermore, both sagittal plane hip and knee maximum joint flexion were significantly higher with increasing heights of the obstacles during negotiation. These data provide insight on segment mechanics within a non-mobility-impaired population; therefore, providing a baseline to understand the kinematic demands necessary for safe and effective gait in mobility-compromised populations. Anat Rec, 300:732-738, 2017. © 2017 Wiley Periodicals, Inc.

Reliability and concurrent validity of standardized walking obstacle course test in people with stroke.

To investigate: (i) the intra-rater, inter-rater and test-retest reliabilities of completion times and step counts on the Standardized Walking Obstacle Course test (SWOC); (ii) correlations between SWOC scores and stroke-specific impairments; (iii) the cut-off SWOC completion times and step counts for distinguishing differences in obstacle negotiation ability in people with chronic stroke and healthy older adults. Cross-sectional study. University-based rehabilitation centre. Twenty-nine people with stroke and 30 healthy older adults. SWOC completion times and step counts were measured under 3 conditions: (i) normal walking; (ii) walking with a tray; and (iii) walking with dark-glasses. The Fugl-Meyer Assessment of lower extremity, the Five-Times-Sit-to-Stand Test, the Berg Balance Scale, the Timed Up and Go Test (TUG), and the Community Integration Measure questionnaire, were also administered. SWOC completion times and step counts showed very satisfactory to excellent reliabilities (intraclass correlation coefficient; ICC = 0.851-0.993). TUG times correlated significantly with SWOC completion times and step counts under the 3 conditions (r = 0.586-0.815, p < 0.001). SWOC completion times of 14.73-16.00 s and step counts of 23.06-24.13, depending on different walking conditions, were able to discriminate between stroke survivors and healthy older adults. The SWOC is a reliable clinical tool for assessing obstacle negotiation ability in people with stroke.

Capability Analysis and Motion Planning for Obstacle Negotiation of a Closed Five-bow-shaped-bar Linkage

Capability Analysis and Motion Planning for Obstacle Negotiation of a Closed Five-bow-shaped-bar Linkage

Research on the Obstacle Negotiation Strategy for the Heavy-duty Six-legged Robot based on Force Control

To make heavy-duty six-legged robots without environment reconstruction system negotiate obstacles after the earthquake successfully, an obstacle negotiation strategy is described in this paper. The reflection strategy is generated by the information of plantar force sensors and Bezier Curve is used to plan trajectory. As the heavy-duty six-legged robot has a large inertia, force controller is necessary to ensure the robot not to lose stability while negotiating obstacles. Impedance control is applied to reduce the impact of collision and active force control is applied to adjust the pose of the robot. The robot can walk through zones that are filled with obstacles automatically because of force control. Finally, the algorithm is verified in a simulation environment.