Identifying Trippers and Non-Trippers Based on Knee Kinematics During Obstacle-Free Walking

Trips are a major cause of falls. Sagittal-plane kinematics affect clearance between the foot and obstacles, however, it is unclear which kinematic measures during obstacle-free walking are associated with avoiding a trip when encountering an obstacle. The purpose of this study was to determine kinematic factors during obstacle-free walking that are related to obstacle avoidance ability. It was expected that successful obstacle avoidance would be associated with greater peak flexion/dorsiflexion and range of motion (ROM), and differences in timing of peak flexion/dorsiflexion during swing of obstacle-free walking for the hip, knee and ankle. Three-dimensional kinematics were recorded as 35 participants (young adults age 18–45 (N = 10), older adults age 65+ without a history of falls (N = 10), older adults age 65+ who had fallen in the last six months (N = 10), and individuals who had experienced a stroke more than six months earlier (N = 5)) walked on a treadmill, under obstacle-free walking conditions with kinematic features calculated for each stride. A separate obstacle avoidance task identified trippers (multiple obstacle contact) and non-trippers. Linear discriminant analysis with sequential feature selection classified trippers and non-trippers based on kinematics during obstacle-free walking. Differences in classification performance and selected features (knee ROM and timing of peak knee flexion during swing) were evaluated between trippers and non-trippers. Non-trippers had greater knee ROM (P = .001). There was no significant difference in classification performance (P = .193). Individuals with reduced knee ROM during obstacle-free walking may have greater difficulty avoiding obstacles

Stepping over obstacles: Attention demands and aging

Older adults have been shown to trip on obstacles despite taking precautions to step carefully. It has been demonstrated in dual-task walking that age-related decline in cognitive and attentional mechanisms can compromise postural management. This is yet to be substantiated during obstacle negotiation when walking. Forty-six healthy volunteers (aged 20-79 years) stepped over obstacles in their path whilst walking and performing a verbal fluency task. Using 3D kinematic analysis we compared obstacle crossing during single (obstacle crossing only) and dual-task (obstacle crossing with verbal task) conditions. We grouped the participants into three age groups and examined age-related changes to cognitive interference on obstacle crossing. During dual-task trials, the 20-29 and 60-69 groups stepped closer to the obstacles prior to crossing, increased vertical toe-obstacle clearance, and had reduced gait variability. In these two groups there was a small dual-task decrease in verbal output. The 70-79 group applied similar dual-task stepping strategies during pre-crossing. However, during crossing they showed reduced vertical toe-to-obstacle clearance and increased variability of obstacle-to-heel distance. Additionally, this group did not show any significant change to verbal output across trials. These results suggest that with advanced age, increased cognitive demands are more likely to have a detrimental impact on motor performance, leading to compromised safety margins and increased variability in foot placement. We conclude that younger adults utilise a posture-preserving strategy during complex tasks but the likelihood of this strategy being used decreases with advanced age

Effects of obesity on walking patterns and adaptability during obstacle crossing

Obesity is a worldwide public health epidemic with no sign of yet abating. Although previous studies have examined the impact of obesity on walking, little is known about the effects of practice on walking patterns in individuals with obesity. The purpose of this current study was to evaluate whether an obstacle-crossing task may detect walking deficits in a group of adults electing to undergo bariatric surgery. With a cross-sectional design, we collected walking parameters as 24 adults (M age= 46.19, SD= 12.90) with obese body mass index (BMI) scores (M BMI= 41.68, SD= 5.80) and 26 adults (M age= 21.88, SD= 3.48) with normal BMI scores (M BMI= 23.09, SD= 4.47) walked in 5 conditions for 5 trials each: on flat ground, crossing over low, medium, and high obstacles, and again on flat ground. The timing and distance of participants' steps were collected with a mechanized gait carpet (GAITRite, Inc.). We conducted 5 (condition) repeated measures (RM) ANOVAs on our main dependent variables, which measured how fast (velocity) and long (step length) participants' steps were and how much time they spent with one (single limb support time) versus two (double limb support time) feet on the ground. The results showed within session improvements in participants' walking patterns. Comparisons of the first and last trials on flat ground showed that participants took longer, faster steps by increasing step length and velocity (ps<.01). They also spent more time with one versus two feet on the ground via increased single limb support time and decreased double limb support time (ps<.001). Our findings suggest that an obstacle-crossing task may help spur improvements in walking patterns even before adults elect to undergo bariatric surgery

Visual Search Behavior in Individuals With Retinitis Pigmentosa During Level Walking and Obstacle Crossing

Purpose: Investigate the visual search strategy of individuals with retinitis pigmentosa (RP) when negotiating a floor-based obstacle compared with level walking, and compared with those with normal vision. Methods: Wearing a mobile eye tracker, individuals with RP and normal vision walked along a level walkway or walked along the walkway negotiating a floor-based obstacle. In the level walking condition, tape was placed on the floor to act as an object attracting visual attention. Analysis compared where individuals looked within the environment. Results: In the obstacle compared with level walking condition: (1) the RP group reduced the length of time and the number of times they looked Ahead, and increased the time and how often they looked at features on the ground (Object and Down, P < 0.05); and (2) the visual normal group reduced the time (by 19%) they looked Ahead (P = 0.076), and increased the time and how often they looked at the Object (P < 0.05). Compared with the normal vision group, in both level walking and obstacle conditions, the RP group reduced the time looking Ahead and looked for longer and more often Down (P < 0.05). Conclusions: The RP group demonstrated a more active visual search pattern, looking at more areas on the ground in both level walking and obstacle crossing compared with visual normals. This gaze strategy was invariant across conditions. This is most likely due to the constricted visual field and inability to rely on inferior peripheral vision to acquire information from the floor within the environment when walking

Do people with Parkinson’s disease look at task relevant stimuli when walking? An exploration of eye movements

Eye movements are impaired by Parkinson's disease (PD) although limited research has explored if PD affects the relevance of visual fixations when walking. Visual fixations may provide crucial contextual information for safe navigation and important insights into fall risk. This study aimed to: investigate visual fixations made while walking under a range of conditions in PD; identify their task relevance; and explore their relationship with clinical features. Thirty-eight people with mild-moderate PD and forty age-matched control participants completed a straight walk with (i) no additional stimuli and (ii) with additional stimuli (visual cues or a high contrast obstacle), whilst wearing a mobile eye-tracker. Fixations were extracted and classified by location and relevance. PD participants made proportionally fewer task-relevant fixations (floor, walls and additional stimuli ahead), caused by significantly more task-irrelevant fixations (floor, walls and ceiling away from waking path) during normal walking (p = 0.014). These group differences were not apparent with visual cues (p = 0.359). During obstacle crossing trials, PD made significantly more task-relevant fixations than controls (p = 0.007). Reduced bilateral visual acuity was associated with fewer fixations in PD. Our findings suggest that people with PD visually explore complex environments less efficiently likely owing to underlying PD pathology. Visual exploration improved with the addition of salient stimuli (for example visual cues or an obstacle) and thus developing and optimising visual interventions could prove critical to improving locomotor safety and reducing falls risk in home environments

Restricting ankle motion via orthotic bracing reduces toe clearance when walking over obstacles.

yesBackground: When trans-tibial amputees cross obstacles leading with their prosthesis, foot clearance is achieved using compensatory swing-phase kinematics. Such compensation would suggest able-bodied individuals normally use swing-phase ankle dorsiflexion to attain adequate obstacle clearance, however, direct evidence of such contribution is equivocal. The present study determined the contribution of sagittal plane ankle motion in achieving lead-limb clearance during obstacle negotiation. Methods: 12 male able-bodied individuals (ages 18-30) completed obstacle crossing trials while walking on a flat surface. Lead-limb (right) ankle motion was manipulated using a knee-ankle-foot orthosis. Trials were completed with the ankle restricted at a neutral angle or unrestricted (allowing ~ ±15 plantar/dorsiflexion). Findings: Restricted ankle motion caused significant increase in trail-limb foot placement distance before the obstacle (p=0.005); significant decrease in vertical toe clearance (p<0.003), vertical heel clearance (p=0.045) and lead-limb foot placement distance after the obstacle (p=0.045); but no significant changes in knee angle at instant of crossing or in average walking speed. Interpretation: The shifts in foot placements altered the part of swing that the lead-limb was in when the foot crossed the obstacle, which led to a decrease in clearance. These adaptations may have been due to being unable to dorsiflex the ankle to ‘lift’ the toes in mid-swing or to being unable to plantarflex the ankle during initial contact following crossing, which changed how the lead-limb was to be loaded. These findings suggest individuals using ankle bracing or those with ankle arthrodesis, will have reduced gait safety when negotiating obstacles

User Equilibrium Route Assignment for Microscopic Pedestrian Simulation

For the simulation of pedestrians a method is introduced to find routing alternatives from any origin position to a given destination area in a given geometry composed of walking areas and obstacles. The method includes a parameter which sets a threshold for the approximate minimum size of obstacles to generate routing alternatives. The resulting data structure for navigation is constructed such that it does not introduce artifacts to the movement of simulated pedestrians and that locally pedestrians prefer to walk on the shortest path. The generated set of routes can be used with iterating static or dynamic assignment methods

Kinematic strategies in newly walking toddlers stepping over different support surfaces

In adults, locomotor movements are accommodated to various support surface conditions by means of specific anticipatory locomotor adjustments and changes in the intersegmental coordination. Here we studied the kinematic strategies of toddlers at the onset of independent walking when negotiating various support surface conditions: stepping over an obstacle, walking on an inclined surface, and on a staircase. Generally, toddlers could perform these tasks only when supported by the arm. They exhibited strategies very different from those of the adults. Although adults maintained walking speed roughly constant, toddlers markedly accelerated when walking downhill or downstairs and decelerated when walking uphill or upstairs. Their coordination pattern of thigh-shank-foot elevation angles exhibited greater inter-trial variability than that in adults, but it did not undergo the systematic change as a function of task that was present in adults. Thus the intersegmental covariance plane rotated across tasks in adults, whereas its orientation remained roughly constant in toddlers. In contrast with the adults, the toddlers often tended to place the foot onto the obstacle or across the edges of the stairs. We interpret such foot placements as part of a haptic exploratory repertoire and we argue that the maintenance of a roughly constant planar covariance--irrespective of the surface inclination and height--may be functional to the exploratory behavior. The latter notion is consistent with the hypothesis proposed decades ago by Bernstein that, when humans start to learn a skill, they may restrict the number of degrees of freedom to reduce the size of the search space and simplify the coordination