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Results 601 - 650 of 883
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Guerraz M M Institute of Neurology, The National Hospital for Neurology and Neurosurgery, London, - - 2000
Visual control of postural sway during quiet standing was investigated in normal subjects to see if motion parallax cues were able to improve postural stability. In experiment 1, six normal subjects fixated a fluorescent foreground target, either alone or in the presence of full room illumination. The results showed that ...
Schmitz J - - 2000
The interaction of two feedback loops was investigated: one regulating cuticular stress in the stick insect's leg and the other controlling leg posture. Exclusive stimulation of either of the two relevant sense organs, the load-sensitive trochantero-femoral campaniform sensilla (CS) or the position-/movement-sensitive ventral coxal hairplate (cxHPv), elicits resistance reflex responses ...
Bouisset S - - 2000
Anticipatory postural adjustments (APA), are known to precede the onset of voluntary movement. The aim of this study was to determine whether APA amplitude and duration are programmed identically according to the voluntary movement parameters. Subjects performed shoulder flexions at maximal and sub-maximal velocities, with and without an additional inertial ...
Yen T Y - - 2000
Spectral analysis of continuously measured joint angles using an electrogoniometer was considered as a potentially efficient method for quantifying exposure to physical stress in repetitive manual work. The method was previously demonstrated in the laboratory but has not yet been tested extensively in the field. Spectral analysis was compared against ...
Keshner E A - - 2000
We examined the effect of a 3-dimensional stereoscopic scene on segmental stabilization. Eight subjects participated in static sway and locomotion experiments with a visual scene that moved sinusoidally or at constant velocity about the pitch or roll axes. Segmental displacements, Fast Fourier Transforms, and Root Mean Square values were calculated. ...
Delleman N J - - 2000
In the study maintenance workers were involved in pneumatic wrenching, oxy-gas cutting, and grinding at 5 different heights. Working posture and workers' perceptions were measured. Guidelines on working height were formulated in order to minimize the load on the musculoskeletal system. Data from the present experiment as well as from ...
Bringoux L - - 2000
The purpose of this study was to investigate how experts in motor skills requiring a fine postural control perceive their body orientation with few gravity based sensory cues. In Experiment 1, expert gymnasts and controls had to detect their body tilt when pitching at a velocity of 0.05 deg.s(-1), in ...
Lackner J R JR Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, Waltham, MA 02454-9110, USA. - - 2000
Our goal is to summarize what has been learned from studies of human movement and orientation control in weightless conditions. An understanding of the physics of weightlessness is essential to appreciate the dramatic consequences of the absence of continuous contact forces on orientation and posture. Eye, head, arm, leg, and ...
Grasso R - - 2000
Human erect locomotion is unique among living primates. Evolution selected specific biomechanical features that make human locomotion mechanically efficient. These features are matched by the motor patterns generated in the CNS. What happens when humans walk with bent postures? Are normal motor patterns of erect locomotion maintained or completely reorganized? ...
Rabin E - - 1999
Postural sway during quiet stance is attenuated by actively maintained contact of the index finger with a stationary surface, even if the level of applied force (<1 N) cannot provide mechanical stabilization. In this situation, changes in force level at the fingertip lead changes in center of foot pressure by ...
Fung J - - 1999
Standing is a dynamic task that requires antigravity support of the body mass and active regulation of the position of the body center of mass. This study examined the extent to which the chronic spinal cat can maintain postural orientation during stance and adapt to changes in stance distance (fore-hindpaw ...
Fukuoka Y - - 1999
In the present study, the visual feedback system in postural control was investigated. To suppress the vestibular and proprioceptive feedback paths, a subject stood on a force-measuring plate with a fixed back support. Because the subject's body was immovable under these conditions, the subject controlled a computer model which simulated ...
Stapley P J PJ Groupe d'Analyse du Mouvement (GAM), UFR STAPS BP 27877, Université de Bourgogne, F-21078 Dijon Cedex, - - 1999
The whole-body center of mass (CoM) has been classically regarded as the stabilized reference value for human voluntary movements executed upon a fixed base of support. Axial synergies (opposing displacements of head and trunk with hip segments) are believed to minimize antero-posterior (A/P) CoM displacements during forward trunk movements. It ...
Kuno S - - 1999
PURPOSE: Human posture is controlled by a combination of vestibular, somatosensory and visual information. This paper is concerned with postural readjustment responses induced by vection. In the visual control of posture, visually-induced perception of self-motion plays an important role and is called vection. Vection is difficult to measure quantitatively because ...
Yonekawa Y - - 1999
The objective of the present study was to determine perception thresholds for whole-body vibration in the recumbent supine posture in vertical and horizontal directions and to compare the present results with ones obtained at the same laboratory in 1984 and also with ISO frequency weighting curves both in ISO 2631-1 ...
Runge C F - - 1999
Previous studies have identified two discrete strategies for the control of posture in the sagittal plane based on EMG activations, body kinematics, and ground reaction forces. The ankle strategy was characterized by body sway resembling a single-segment-inverted pendulum and was elicited on flat support surfaces. In contrast, the hip strategy ...
Bardy B G - - 1999
The coordination of multiple body segments (torso and legs) in the control of standing posture during a suprapostural task was studied. The analysis was motivated by dynamical theories of motor coordination. In 2 experiments it was found that multisegment postural coordination could be described by the relative phase of rotations ...
Baroni G G Bioengineering Center, Politecnico di Milano - Fondazione Pro Juventute Don Carlo Gnocchi, Via Gozzadini 7, I-20148 Milano, Italy, - - 1999
Orbital microgravity represents a unique environment, which allows the isolation of variables assumed to be involved in the mechanism of body positioning in space. In this context, the alignment of the trunk axis along allocentric references and the positioning of the body center of mass inside the supporting base compete ...
Marin L - - 1999
In this study, we considered the interacting effects of expertise in gymnastics, the type of support surface and the required frequency of head movement on the emergence of postural modes of coordination. A group of elite female gymnasts and a control group of non-gymnasts were asked to track the fore-aft ...
Pai Y C - - 1999
Slipping during various kinds of movement often leads to potentially dangerous incidents of falling. The purpose of this study was to determine whether there was evidence to support the theory that movement strategies could be used by individuals to regain stability during an episode of slipping and whether forced sliding ...
Serina E R - - 1999
Awkward upper extremity postures and repetitive wrist motions have been identified by some studies as risk factors for upper extremity musculoskeletal disorders during keyboard work. However, accurate body postures and joint motions of typists typing on standardized workstations are not known. A laboratory study was conducted to continuously measure wrist ...
Siegmund G P - - 1999
Prior two-way analyses of variance showed that the peak kinematic response of the head and neck of subjects exposed to low-speed rear-end collisions was related to speed change and gender, however potential reasons for this gender dependence were not determined. Using multiple linear regression, this study further examined these response ...
Saw S M - - 1999
PURPOSE: To develop measures and indices of factors (distance of eye from object, posture, and lighting) that may modify a possible effect of near work activity on myopia. METHODS: The duration of near work, the distance of an object from eye, lighting conditions, and other sociodemographic characteristics were asked in ...
Mittelstaedt H - - 1999
The role of the otoliths in essential performances of human orientation is analyzed. The following interactions of the otoliths are considered: 1. The otoliths cooperate with graviceptors in the trunk in the perception of body posture. The truncal graviceptors turn out to yield on average 60% of the total gain. ...
Buchanan J J - - 1999
Emergence of postural patterns as a function of vision and translation frequency. We examined the frequency characteristics of human postural coordination and the role of visual information in this coordination. Eight healthy adults maintained balance in stance during sinusoidal support surface translations (12 cm peak to peak) in the anterior-posterior ...
Perreault E J - - 1999
This study presents time-domain and frequency-domain, multiple-input, multiple-output (MIMO) linear system identification techniques that can be used to estimate the dynamic endpoint stiffness of a multijoint limb. The stiffness of a joint or limb arises from a number of physiological mechanisms and is thought to play a fundamental role in ...
Golomer E - - 1999
We investigated the involvement of vision in the regulation of dynamic equilibrium in male children and young adults performing a physical activity requiring a high level of spatial skill: self-induced body sways of ballet dancers on a free unstable platform, 45 professional male dancers (Paris Opera) participated in the study. ...
Clapp S S MRC APU, Cambridge, - - 1999
It has previously been shown that light contact with the finger tip on a fixed surface reduces centre of pressure (CoP) fluctuations in the frontal plane when standing in an unstable posture with the feet in line (tandem Romberg stance). Positive cross-correlations between horizontal finger forces and CoP fluctuations with ...
Kamper D - - 1999
The postural stability of wheelchair users experiencing external perturbations was examined. Rotation of a tilt platform generated moments in the trunks of subjects seated in a manual wheelchair on the platform. The magnitude and duration of the moments were on the order of those that might be encountered in the ...
Hlavacka F - - 1999
We compared the effects of galvanic vestibular stimulation applied at 0, 0.5, 1.5 and 2.5 s prior to a backward platform translation on postural responses. The effect of the galvanic stimulation was largest on the final equilibrium position of the center of pressure (CoP). The largest effects occurred for the ...
Riley M A - - 1999
A technique (recurrence quantification analysis; RQA) for analyzing center of pressure (COP) signals is presented and applied to data obtained by having participants stand with the head forward or sideways and with eyes open or closed. RQA is suitable for short, nonstationary signals and quantifies dynamical (deterministic) structure and nonstationarity. ...
Pavlik A E AE Center for BioDynamics and Department of Biomedical Engineering, Boston University, MA 02215, - - 1999
Galvanic vestibular stimulation serves to modulate the continuous firing level of the peripheral vestibular afferents. It has been shown that the application of sinusoidally varying, bipolar galvanic currents to the vestibular system can lead to sinusoidally varying postural sway. Our objective was to test the hypothesis that stochastic galvanic vestibular ...
Tang P F - - 1999
BACKGROUND: Phase-dependent modulation of postural responses plays an important functional role in integrating reflexes into ongoing locomotion behaviors. This study tested the hypotheses that proximal and distal postural responses are modulated differently according to the phases of the gait cycle in young adults and that there is a decline in ...
Nagy E - - 1999
We examined the horizontal and vertical component of diagonal optokinetic nystagmus (DOKN) in sitting posture and in the last 15 minutes of antiorthostatic posture at -30 degrees lasting 3 hours. The antiorthostatic posture is suited to the earthy model of the fluid shifting observed in microgravity. We found that the ...
Gilles M M Centre for Advanced Studies in Sensory Motor Neuroscience, School of Psychology, The University of Birmingham, Edgbaston, - - 1999
The effect of the predictability of perturbation to standing balance was evaluated in terms of the muscle activity and response dynamics of five subjects exposed to horizontal forces at the pelvis producing sideways or forward sway. Rapid (EMG onset latencies of 70-80 ms recorded from the left gluteus medius and ...
Beaudoin L - - 1999
A small leg length inequality, either true or functional, can be implicated in the pathogenesis of numerous spinal disorders. The correction of a leg length inequality with the goal of treating a spinal pathology is often achieved with the use of a shoe lift. Little research has focused on the ...
Duarte M - - 1999
Prolonged (>30 min) unconstrained standing (PUS) was studied in 10 young healthy subjects. The usual methods of stabilographic analysis assume a random center of pressure (COP) migration. This study was based on the opposite idea and showed that during PUS, specific and consistent patterns of the COP migration can be ...
Borger L L - - 1999
Postural sway during stance has been found to be sensitive to moving visual scenes in young adults, children, and those with vestibular disease. The effect of visual environments on balance in elderly individuals is relatively unknown. The purpose of this study was to compare postural sway responses of healthy elderly ...
Snook S H - - 1999
Psychophysics is a very old branch of psychology that is concerned with the relationship between physical stimuli that occur in the "outside world", and the sensations they produce in the body's "inside world". According to modern psychophysical theory, the strength of a sensation is directly related to the intensity of ...
Allum JH - - 1998
The assumption that proprioceptive inputs from the lower legs are used to trigger balance and gait movements is questioned in this review (an outgrowth of discussions initiated during the Neural Control of Movement Satellite meeting held in Cozumel, Mexico, April 1997). Recent findings presented here suggest that trunk or hip ...
Hashiba M - - 1998
Postural sway was measured in 24 healthy subjects after running or walking with eyes open on a standard treadmill exerciser. The speeds of running and walking were set at 10 and 7 km/h, respectively, and locomotion was maintained for 7 min. The postural sway response was characterized by systematic forward ...
Burgess-Limerick R. - - 1998
OBJECTIVE:: The objectives were to determine the postural consequences of varying computer monitor height and to describe self-selected monitor heights and postures. DESIGN:: The design involved experimental manipulation of computer monitor height, description of self-selected heights, and measurement of posture and gaze angles. BACKGROUND: Disagreement exists with regard to the ...
Messing K - - 1998
Work is organized based in part on the perceptions, by managers and workers, of workers, their abilities and the characteristics of the work to be done. Physical tasks in factories and services have often been divided into 'light' and 'heavy', a division that often corresponds formally or informally to gender. ...
Cobb S V - - 1998
The aim of this experiment was to measure the effect of immersion in a virtual environment (VE) on postural stability and examine the relationship between postural stability and self-reported simulator sickness. Forty healthy subjects were exposed to 20 min of immersion in an interactive VE with restricted user movement. The ...
Mergner T - - 1998
This article considers the intersensory interaction mechanisms and biomechanical aspects of human spatially oriented behavior and asks to what extent these are interrelated on earth by gravity and how they might be affected under microgravity. The interactions between vestibular, somatosensory and visual inputs for postural control are obscured by several ...
Kavounoudias A - - 1998
This study investigated the role of the plantar cutaneous information in controlling human balance. We hypothesized that the cutaneous afferent messages from the main supporting zones of the feet have sufficient spatial relevance to inform the CNS about the body position with respect to the vertical reference and consequently to ...
Speers R A - - 1998
Postural and gait instabilities in astronauts returning from spaceflight are thought to result from in-flight adaptation of central nervous system processing of sensory inputs from the vestibular, proprioceptive, and visual systems. We hypothesized that reorganization of posture control relying on these multiple inputs would result in not only greater amounts ...
MacKinnon S N - - 1998
This paper investigates the differences in maximal isometric horizontal pull forces in the sagittal plane about a frontal plane work envelope. Eight subjects produced maximal isometric horizontal pulls about 32 positions in the frontal for each of three different postural conditions: free standing, fixed standing and seated. Four horizontal positions ...
Szturm T - - 1998
Different movement synergies used to restore balance in response to sudden support surface displacements have been described, which include the ankle movement synergy and a number of multisegmental movement synergies. The purpose of this study was to extend the analysis of the effects of stimulus magnitude on the pattern and ...
Kuo A D AD Department of Mechanical Engineering and Applied Mechanics, University of Michigan, Ann Arbor 48109-2125, USA. - - 1998
Multivariate descriptors of sway were used to test whether altered sensory conditions result not only in changes in amount of sway but also in postural coordination. Eigenvalues and directions of eigenvectors of the covariance of shnk and hip angles were used as a set of multivariate descriptors. These quantities were ...
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