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Assane E.S. Niang and Bradford J. McFadyen

The present study investigated the adaptations of specific power bursts during the combined contexts of the proximity (lead vs. trail limb) and height of an obstruction in relation to limb elevation versus progression. Ten young, adult, male subjects walked at their natural speed during unobstructed walking and the bilateral avoidance of moderate and high obstacles. Hip flexor generation power was unaffected by obstacle height for the leading limb and always delayed for the trailing limb. The knee extensor absorption power burst at toe-off was also eliminated for the trailing limb and was found to reappear in mid-swing. Few differences were seen for ankle push-off power. The results suggest that the hip joint is dedicated to limb advancement only, while the knee joint is directly involved in limb elevation and the control of multiarticular effects.

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Deborah A. Jehu, Yves Lajoie and Nicole Paquet

Tripping has been suggested to be one of the main causes of falls in older adults ( Berg, Alessio, Mills, & Tong, 1997 ), with the majority of trips occurring during obstacle negotiation ( Overstall, Exton-Smith, Imms, & Johnson, 1977 ) and in a dual-task context ( Tideiksaar, 1996 ). Older adults

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Chanel T. LoJacono, Ryan P. MacPherson, Nikita A. Kuznetsov, Louisa D. Raisbeck, Scott E. Ross and Christopher K. Rhea

Obstacles are a naturally occurring part of our daily environment when defined as any physical object that requires an individual to modulate their current gait pattern. Obstacles, such as stairs, curbs, and puddles, are stationary and allow for a slow and early adaptation of the gait pattern

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Seung-uk Ko, Gerald J. Jerome, Eleanor M. Simonsick and Luigi Ferrucci

of performance impairment, which, in turn, may lead to more effective prevention of age-associated mobility decline. In gait analysis, use of more challenging tasks, such as obstacle crossing, places additional demands on the lower limbs ( Kuo et al., 2017 ; Ma et al., 2017 ) and thus can elucidate

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Lana M. Pfaff and Michael E. Cinelli

Individuals successfully avoid obstacles under various environmental conditions whether the obstacles are stationary ( Hackney, Vallis, & Cinelli, 2013 ; Higuchi et al., 2011 ; Knowles, Kreuser, Haas, Hyde, & Schuchart, 1976 ; Wilmut & Barnett, 2010 ) or moving ( Cinelli, Patla, & Allard, 2009

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Jean Jose da Silva, Fabio Augusto Barbieri and Lilian Teresa Bucken Gobbi

Crossing moving obstacles requires different space-time adjustments compared with stationary obstacles. Our aim was to investigate gait spatial and temporal parameters in the approach and crossing phases of a moving obstacle. We hypothesized that obstacle speed affects gait parameters, which allow us to distinguish locomotor strategies. Ten young adults walked and stepped over an obstacle that crossed their way perpendicularly, under three obstacle conditions: control—stationary obstacle, slow (1.07m/s) and fast speed (1.71m/s) moving obstacles. Gait parameters were different between obstacle conditions, especially on the slow speed. In the fast condition, the participants adopted predictive strategies during the approach and crossing phases. In the slow condition, they used an anticipatory strategy in both phases. We conclude that obstacle speed affects the locomotor behavior and strategies were distinct in the obstacle avoidance phases.

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David Silva, Ronaldo Gabriel, Helena Moreira, João Abrantes and Aurélio Faria

fallers and non-fallers, only a small number of quantitative studies have found gait measures that can differentiate these groups ( Hausdorff, Rios, & Edelberg, 2001 ). Overcoming obstacles and imbalances during gait are significantly challenging for the elderly and account for approximately 50% of falls

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Deborah A.M. Jehu, Nicole Paquet and Yves Lajoie

Tripping is a major concern in the older adult population as it is a main cause of falls ( Berg, Alessio, Mills, & Tong, 1997 ). Nearly 50% of falls in community-dwelling older adults occur during destabilizing activities, such as stepping over obstacles and negotiating raised surfaces ( Tinetti

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Marcos Rodrigo Trindade Pinheiro Menuchi and Lilian Teresa Bucken Gobbi

Locomotion generates a visual movement pattern characterized as optic flow. To explore how the locomotor adjustments are affected by this pattern, an experimental paradigm was developed to eliminate optic flow during obstacle avoidance. The aim was to investigate the contribution of optic flow in obstacle avoidance by using a stroboscopic lamp. Ten young adults walked on an 8m pathway and stepped over obstacles at two heights. Visual sampling was determined by a stroboscopic lamp (static and dynamic visual sampling). Three-dimensional kinematics data showed that the visual information about self-motion provided by the optic flow was crucial for estimating the distance from and the height of the obstacle. Participants presented conservative behavior for obstacle avoidance under experimental visual sampling conditions, which suggests that optic flow favors the coupling of vision to adaptive behavior for obstacle avoidance.

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Jonathan Vaughan, David A. Rosenbaum and Ruud G. J. Meulenbroek

In this article, we review a model of the movement-planning processes that people use for direct reaching, reaching around obstacles, and grasping, and we present observations of subjects' repeated movements of the hand to touch 2 target locations, circumventing an intervening obstacle. The model defines an obstacle as a posture that, if adopted, would intersect with any part of the environment (including the actor himself or herself). The model finds a trajectory that is likely to bring the end-effector to me target by means of a one- or two-stage planning process. Each stage exploits the principles of instance retrieval and instance generation. In the first stage, a goal posture is identified, and the trajectory of a direct transition to that posture is tested for collision. If that direct movement has no collision, the movement to the target is immediately executed in joint space. If. however, the direct movement is foreseen to result in a collision, a second planning stage is invoked. The second planning stage identifies a via posture, movement through which will probably avoid the collision. Movement to and from the via posture is then superimposed on the main movement to the target so that the combined movement reaches the target without colliding with intervening obstacles. We describe the details of instance retrieval and instance generation for each of these planning stages and compare the model's performance with the observed kinematics of direct movements as well as movements around an obstacle. Then we suggest how the model might contribute to the study of movements in people with motor disorders such as spastic hemiparesis.