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Winter D A - - 1998
Our goal was to provide some insights into how the CNS controls and maintains an upright standing posture, which is an integral part of activities of daily living. Although researchers have used simple performance measures of maintenance of this posture quite effectively in clinical decision making, the mechanisms and control ...
Salomon R - - 1998
This paper proposes a new self-organizing, biologically-inspired control architecture for mobile robots consisting of a controller and a value system. The controller uses activity patterns of visual sensors to determine the motor commands, whereas the value system receives stimuli from proprioceptive sensors. This design decision is justified by the following ...
Aruin A S - - 1998
OBJECTIVES: The purpose of this study was to investigate anticipatory postural adjustments (APAs) in standing subjects who performed a standard motor action triggering a standard postural perturbation (releasing a 2.2 kg load from extended arms) in conditions of different stability requirements. METHODS: The degree of stability was varied either by ...
Kunkel M M Department of Clinical Neurophysiology, University of Goettingen, - - 1998
The present study investigates the efficacy of visual stabilisation of posture for different spatial frequencies of a visual stimulus. Circular sine wave gratings were used to analyse the correlation between perception of motion in depth and stabilisation of fore-aft sway by the mechanism of detecting changes in target size. Body ...
De Wolf S S Faculty of Human Movement Science, Free University, Amsterdam, The - - 1998
We studied the changes in the anticipatory postural adjustments (APAs), associated with dropping a load from extended arms and during fast bilateral shoulder flexion movements, when movements were performed in a self-paced manner and under a simple reaction-time instruction. The latter instruction applied time pressure and did not allow the ...
Clément G - - 1998
Postural reactions induced by vertical optokinetic stimulation were recorded for 5 subjects in a ground-based study, and for one astronaut before, during, and after a 25-day spaceflight. On the ground, the amplitude of visually-induced postural reactions generally increased with stimulus velocity and saturated around 60 degrees/s, with an angle of ...
Hamrick M W - - 1998
This study tests predicted morphoclines in fingertip morphology among four small-bodied (<1 kg) New World monkeys (Saimiri sciureus, Leontopithecus rosalia, Callithrix jacchus, and Saguinus oedipus) in order to test previous functional and adaptive explanations for the evolution of flattened nails, expanded apical pads, and grasping extremities within the Order Primates. ...
Jeka J - - 1998
Light touch contact of a fingertip to a stationary surface provides orientation information that enhances control of upright stance. Slight changes in contact force at the fingertip lead to sensory cues about the direction of body sway, allowing attenuation of sway. In the present study, the coupling of postural sway ...
Cauquil A S - - 1998
Lateral sway of subjects in spontaneous dynamic balance conditions on a seesaw platform was measured during a visual stimulation monocularly produced by a rotating glass covered with a prism membrane. Prism rotation induced the perception of a circular translation of the whole visual field and an ocular pursuit movement. Therefore, ...
Lin M L - - 1998
A previous pilot study demonstrated that a force and frequency-weighted filter network could be developed for processing continuous biomechanical measures of repetitive wrist motions and exertions. The current study achieves the objective by modelling subjective discomfort for repetitive wrist flexion using controlled posture, pace and force. A three-level fractional factorial ...
Timmann D D R.S. Dow Neurological Sciences Institute, Portland, OR 97209, - - 1998
Recent experiments in healthy subjects have demonstrated that automatic postural responses can be suppressed when subjects are instructed to step instead of maintain stance in response to the surface translation. The aim of the present study was to investigate the role of the cerebellum in coordinating this interaction between the ...
Henry S M - - 1998
The purpose of this study was to compare and contrast postural responses to lateral and A/P surface translations by quantifying joint positions, bilateral three-dimensional (3-D) ground reaction forces, and lower limb and trunk muscle electromyographic (EMG) activity. Subjects stood on a movable platform which was randomly translated in four different ...
van Dieën J H - - 1998
In the present study, the effects of repetition on the kinematics in discrete lifting were studied in 10 subjects who lifted a barbell weighing 10% of body mass at a determined speed and along a determined trajectory 630 times during about 40 min. Three-dimensional (3-D) kinematics of the feet, lower ...
Jeka J J - - 1998
The goal of the present study was to determine the properties of the somatosensory stimulus that alter its temporal coupling to body sway. Six standing subjects were tested while touching a metal plate positioned either directly in front of or lateral to the subject. In each condition, the plate moved ...
Lee M Y - - 1998
The purpose of this study was to explore whether we could provide supportive laboratory evidence for clinical observations that a stroke patient has lost functional mobility/locomotion capability based on dynamic balance responses (centre of pressure, COP sway patterns) and motor control activities (EMG patterns) during the motor task of sit-to-stand. ...
Caron O - - 1997
This study proposes to estimate the horizontal positions of the body's centre of gravity (CoG) in a standing posture, on the basis of the horizontal positions of the centre of pressure (CoP). The latter were measured with a force plate, and using a low-pass filter defined by a mathematical relationship ...
Riley M A MA Center for the Ecological Study of Perception and Action, Department of Psychology, University of Connecticut, Storrs 06269, USA. - - 1997
Subjects stood upright with the index finger of the right hand either touching a nearby surface gently or not touching it at all and with the eyes either open or closed. Trajectories of the center of pressure (COP) were analyzed as fractional Brownian motion. The extracted parameters were the effective ...
Lacquaniti F - - 1997
Studies are reviewed that address the problem of the variables controlled in the maintenance of body posture and generation of limb movement. Vestibulospinal and neck reflexes cancel each other in response to roll, but not in response to pitch of the animal. In pitch trunk orientation is not effectively stabilized ...
Fahrenberg J - - 1997
Modern assessment of posture and motion involves the use of wide bandwidth piezoresistive accelerometers. The direct current (DC) component allows for assessment of slow motion and change in position referring to the gravitational axis: the alternating current (AC) component, calibrated in g. represents acceleration along the sensitive axis of the ...
Donaldson N de N Nde - - 1997
Apparatus has been built to explore the practical feasibility of using automatic control with electrical stimulation of paralysed legs to restore function. The experiments are performed with paraplegics with the aim of achieving a realistic postural task: to see whether the body may be maintained upright by stimulation of the ...
Lee M Y - - 1997
This study was undertaken to explore whether we could provide supportive laboratory evidence for the clinical observations that a stroke patient has lost functional mobility/locomotion capability based on dynamic balance responses (center of force sway patterns) and motor control activities (electromyography patterns) during the motor task of sit-to-stand. A computerized ...
Slobounov S. M - - 1997
This article is a report on 3 experiments designed so that the role of virtual time-to-collision (VTC), which specifies the spatiotemporal proximity of the center of pressure to the postural stability boundary in the regulation of posture in upright stances, could be examined. Virtual time-to-collision was estimated for normal upright ...
Benvenuti F - - 1997
In standing humans, it is not certain whether anticipatory postural adjustments associated with rapid, voluntary elbow flexion movements (focal movements) originate as a selection from preset synergies or as the result of specific planning of motor commands. We studied these muscle recruitment patterns when the same focal movement was made ...
Tarantola J - - 1997
The effects of repetition of quiet stance trials on body sway, recorded through a stabilometric platform, were studied in 12 normal subjects. With feet together, both with eyes open (EO) and closed (EC), a progressive shift forward of the centre of foot pressure (CFP) occurred with repetition. In addition, with ...
Lyon I N IN MRC Human Movement and Balance Unit, Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK. - - 1997
During a step the body's centre of mass (CoM) typically remains medial to the supporting foot and therefore the body is unstable and falling (sideways) under gravity. This may make it difficult to adjust the frontal-plane body motion appreciably once the step is under way. We have therefore investigated whether ...
Prochazka A - - 1997
In this paper we review some theoretical aspects of positive feedback in the control of movement. The focus is mainly on new theories regarding the reflexive role of sensory signals from mammalian tendon organ afferents. In static postures these afferents generally mediate negative force feedback. But in locomotion there is ...
Wade M G - - 1997
This article reviews and analyzes the role of vision and spatial orientation in maintaining posture and balance. The key issues that relate to the development of postural control across the life span are discussed. Use of vision as a critical source of information that specifies spatial orientation in the environment ...
Lin M L - - 1997
The relative effects of repetition, force and posture were studied in order to investigate how continuous biomechanical measurements can be combined into a single metric corresponding to subjective discomfort. A full factorial experiment was conducted involving repetitive wrist flexion from a neutral posture to a given angle against a controlled ...
Nichols D S - - 1997
Balance is a somewhat ambiguous term used to describe the ability to maintain or move within a weight-bearing posture without falling. Balance can further be broken down into three aspects: steadiness, symmetry, and dynamic stability. Steadiness refers to the ability to maintain a given posture with minimal extraneous movement (sway). ...
Brown D A - - 1997
With hemiplegia following stroke, a person's movement response to anti-gravity posture often appears rigid and inflexible, exacerbating the motor dysfunction. A major determinant of pathological movement in anti-gravity postures is the failure to adapt muscle-activity patterns automatically to changes in posture. The aim of the present study was to determine ...
Jeka J J - - 1997
Canes and crutches are commonly used mobility aids, and most studies of their use have focused on issues equating support with the resulting decrease in force required of the affected limb. Clinicians, however, often observe patients with poor balance control using light touch of surrounding objects and surfaces to stabilize ...
Schmuckler M A - - 1997
Two experiments examined postural responses of 3- to 6-year-old children to visual information for oscillation. In Experiment 1, children saw oscillations of the surround, with these movements ranging in frequency between 0.2 and 0.8 Hz. Analyses of anterior-posterior postural sway revealed that, similar to previous developmental investigations, the frequency of ...
Hedman T P - - 1997
STUDY DESIGN: In vitro force and deformation measurements formed the basis for determinate, quasistatic analysis of principal forces in the seated lumbar spine. OBJECTIVES: To explore the relationship between seated postures and the mechanical response in component tissues of lumbar intervertebral joints. SUMMARY OF BACKGROUND DATA: Despite the high prevalence ...
Allison G T - - 1997
The purpose of this study was to investigate the influence of a prototype trunk orthosis to assist an individual with tetraplegia. A single case study (26 year old male, C5 motor complete) using an interrupted time series analysis was conducted to investigate the individual's ability to reach, forward and laterally, ...
Burgess-Limerick R - - 1997
Manual lifting techniques are commonly defined in terms of the postures adopted at the start of the lift. Quantitative definition is problematic, however, because the absolute joint angles adopted to lift an object are influenced by task parameters, such as the initial height of the load. We present an argument ...
Burleigh-Jacobs A - - 1997
We studied anticipatory postural adjustments contributing to gait initiation deficits in patients with Parkinson's disease (PD) to determine if these deficits could be improved by administration of levodopa or by external stimuli. Ground reaction forces and body kinematics were recorded for self-generated and cutaneous cue-triggered step initiation in normal subjects ...
Jeka J J JJ Department of Kinesiology, University of Maryland, College Park 20742-2611, USA. - - 1997
Light touch contact of a fingertip with a stationary surface can provide orientation information that enhances control of upright stance. Slight changes in contact force at the fingertip provide sensory cues about the direction of body sway, allowing attenuation of sway. In the present study, we asked to which extent ...
Timmann D - - 1997
We reported previously that patients with cerebellar deficits were unable to scale the magnitude of their early automatic postural responses to the predicted amplitudes of surface translations based on central set from prior experience. The present study investigated whether this deficit in set-dependent amplitude scaling was based predominantly on the ...
Luyat M - - 1997
Three experiments were conducted to test the effect of postural information, resulting from the active control of balance, on the perception of the vertical. Subjects were required to adjust a luminous rod in two different visual contexts: in the dark or within a tilted visual frame. In these experiments, postural ...
Bronstein A M AM MRC Human Movement and Balance Unit, National Hospital for Neurology and Neurosurgery, London, - - 1997
The purpose of this study was to establish whether visual motion parallax participates in the control of postural sway. Body sway was measured in ten normal subjects by photoelectric recordings of head movements and by force-plate posturography. Subjects viewed a visual display ("background"), which briefly moved (2 s) along the ...
Izumi-Kurotani A - - 1997
Japanese tree frogs (Hyla japonica) showed unique postures and behavior during an 8-day flight to the Russian space station Mir. When floating in the air, the animals arched their back and extended their four limbs. This posture resembles that observed during jumping or parachuting of the animals on the ground. ...
Ito Y - - 1997
METHODS: To assess subjective postural orientation and the visual vertical during slow pitch tilt, subjects were seated, restrained and in darkness in a simulator. They estimated when they were tilted 0 degrees, 45 degrees, and 90 degrees forwards and backwards during cycles of pitching tilted at 1 degree x s-1 ...
Smetanin B N - - 1997
Errors in pointing to remembered target locations were measured in normal subjects in the upright posture and in a supine or prone lying position, three conditions that differed in the orientation of the moving arm with respect to gravity. Vertical errors, or, more strictly, errors along the body axis, were ...
Aruin A S - - 1997
OBJECTIVE: We studied the role of adaptive changes within the central nervous system in anticipatory postural adjustments seen in unilateral below-the-knee amputees. DESIGN: Changes in electromyographic and mechanical variables were compared during standardized tasks performed by standing subjects. BACKGROUND: Anticipatory postural adjustments represent an important mechanism of postural control which ...
Loughlin P J - - 1996
To study potential time-varying dynamics of postural sway as measured via center-of-pressure (COP) under the feet, we applied time-frequency analysis to COP data from ten vestibularly impaired subjects and 13 nonimpaired controls, during quiet stance and in response to visual perturbation. This analysis revealed that 1) the spectral characteristics of ...
Kawakami O - - 1996
This study investigated the effects of antero-posterior movement on the upright standing posture in the humans. Subjects were asked to stand on a platform in a linear accelerator (sled) in the dark. At a fixed distance of sled movements in an antero-posterior direction, peak speed was changed by sinusoidal modes ...
Sinha T - - 1996
Previous studies investigating postural control using platform perturbations demonstrated that forward leaning occurs under certain experimental conditions. This study examined a potential benefit of forward leaning, investigating the hypothesis that forward lean acts to increase the effective stiffness of the postural ankle dynamics. A systems modeling approach was used to ...
Bardy B G BG UMR Mouvement & Perception, Faculty of Sport Sciences, University of the Mediterranean, Marseille, France. - - 1996
Three experiments tested the hypothesis that postural sway during locomotion is visually regulated by motion parallax as well as optical expansion. Oscillating displays of three-dimensional scenes were presented to participants walking on a treadmill, while postural sway was recorded. Displays simulated: (a) a cloud, in which parallax and expansion are ...
Warren W H - - 1996
Three experiments examined the functional specificity of visually controlled posture during locomotion by presenting large-screen displays to participants walking on a treadmill. Displays simulated locomotion down a stationary hallway, a hallway that traveled with the observer, or a frontal wall that traveled with the observer. A superimposed oscillation specified postural ...
Horak F B - - 1996
1. This study investigates the effects of parkinsonism and of dopamine replacement therapy (levodopa) on scaling the magnitude of automatic postural responses based on sensory feedback and on predictive central set. Surface reactive torques and electromyographic (EMG) activity in response to backward surface translations were compared in patients with parkinsonism ...
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