Biomedical subjects

Shirley Rietdyk

Publications and source records attributed to Shirley Rietdyk.

4 recordsLinked to original sources

PubMed2006

Control of adaptive locomotion: effect of visual obstruction and visual cues in the environment.

Visual information regarding obstacle position and size is used for planning and controlling adaptive gait. However, the manner in which visual cues in the environment are used in the control of gait is not fully known. This research examined the effect of obstacle position cues on the lead and trail limb trajectories during obstacle avoidance with and without visual information of the lower limbs and obstacle (termed visual exproprioception). Eight subjects stepped over obstacles under four visual conditions: full vision without obstacle position cues, full vision with position cues, goggles without position cues and goggles with position cues. Goggles obstructed visual exproprioception of the lower limbs and the obstacle. Position cues (2 m tall) were placed beside the obstacle to provide visual cues regarding obstacle position. Obstacle heights were 2, 10, 20 and 30 cm. When wearing goggles and without position cues, a majority of the dependent measures (horizontal distance, toe clearance and lead stride length) increased for the 10, 20 and 30 cm obstacles. Therefore lower limb-obstacle visual exproprioception was important for the control of both limbs, even though with normal vision the trail limb was not visible during obstacle clearance. When wearing goggles, the presence of position cues, which provided on-line visual exproprioception of the self relative to the obstacle position in the anterior-posterior direction, returned lead and trail foot placements to full vision values. Lead toe clearance was not affected by the position cues, trail clearance decreased but was greater than values observed during full vision. Therefore, visual exproprioception of obstacle location, provided by visual cues in the environment, was more relevant than visual exproprioception of the lower limbs for controlling lead and trail foot placement.

Adaptation, Physiological↗

PubMed2005

Work experience mitigated age-related differences in balance and mobility during surface accommodation.

BACKGROUND: Locomotor behavior at the roofing worksite is challenged by factors such as sloped surfaces, wind gusts and handling loads. Chronic exposure to this environment may result in enhanced locomotor strategies that are resistant to aging effects. The purpose of this study was to determine if roofers demonstrated enhanced locomotor strategies and if the strategies were maintained with age. METHODS: The gait of ten younger roofers (mean age 27.2 years), eight older roofers (55.4 years), ten younger controls (25.4 years) and nine older controls (57.6 years) was examined during level gait and stepping up onto a wooden surface (0.15m high). Subjects either carried no load, an empty box or the same box loaded to the equivalent of 5% body mass. FINDINGS: Work by age interactions were observed for toe clearance, step width, net angular momentum of the head, arms and trunk segment and gait speed (P<0.0001). Younger roofers demonstrated the greatest toe clearance; older roofers had a smaller lead clearance but decreased variability. Older control groups had the greatest risk of tripping due to low lead toe clearance and high variability, and were least likely to recover if they did trip due to faster gait speed and increased net angular momentum. Work experience resulted in enhanced changes in lead toe clearance and mitigated age-related changes in step width and net angular momentum. INTERPRETATION: Challenging environments show promise for maintaining balance skills in older adults; however care should be taken when introducing inexperienced older adults to a challenging environment.

Adaptation, Physiological↗

PubMed2005

Anticipatory locomotor adjustments of the trail limb during surface accommodation.

This paper explores anticipatory locomotor adjustments of the trail limb when stepping up to a new level. The kinematics and kinetics of the trail limb for nine subjects were compared across level gait and surface accommodation. The largest generation of new rotational energy was found at the trail ankle, during the latter part of stance (i.e. ankle 'push-off'). Accelerations of the head, arms and trunk (HAT) and foot segments during the same phase indicate that the ankle power acted to push the body and lead limb up onto the new level and drive the foot upwards at toe-off. The shank was more vertical at toe-off to ensure that the ankle energy would drive the limb upwards, rather than forward into the surface. The vertical hip translation energy increased over 300%, acting to pull upwards on the hip to increase trail limb elevation. The increased hip translational energy could be due to extension of the lead limb after it was placed on the surface and/or the piston-like drive of the increased rotational energy at the trail ankle during late stance. The findings add to the knowledge of whole body coordination strategies during anticipatory locomotor adjustments when the entire body is raised to a new level.

Acceleration↗

PubMed2005

Proactive stability control while carrying loads and negotiating an elevated surface.

In this study, proactive stability control while handling loads and negotiating an elevated surface was examined. Ten young healthy males completed two gait-mode conditions--level walking and negotiating a raised surface. Load-handling conditions were: no load, empty box (reduced visual information), and loaded box (reduced visual information combined with increased inertial load). The lower limb trajectory in the sagittal plane was not modified as a function of reduced visual information or increased inertial load. The step width decreased while stepping over the surface and carrying the loaded box. The trunk pitch angle was biased backwards for both the empty box and the loaded box. When carrying the empty box and negotiating the surface, the trunk pitch range of motion (ROM) increased which may have been a strategy to increase visual exteroceptive information. As increased net trunk pitch could destabilize the system, concurrent stabilizing strategies--decreased gait velocity and reduced net trunk roll velocity--were observed. To meet the equilibrium goals when carrying the loaded box, the trunk pitch ROM and net pitch velocity were reduced during both level walking and surface accommodation. Trunk roll ROM was reduced when carrying the load and negotiating the surface. This study extends our knowledge regarding whole body coordination strategies during anticipatory locomotor adaptations.

Adult↗