SEARCH · PubMed Health

Results for “Postural control”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

PubMed2005

The functional role of central and peripheral vision in the control of posture.

Three experiments were conducted to investigate the role of central and peripheral vision (CV and PV) in postural control. In Experiment 1, either the central or peripheral visual field were selectively stimulated using a circular random dot pattern that was either static or alternated at 5 Hz. Center of foot pressure (CoP) was used to examine postural sway during quiet standing under both CV and PV conditions. The results showed that, when the visual stimulus was presented in the periphery, the CoP area decreased and more so in the anterior-posterior (AP) than in the medio-lateral (ML) direction, indicating a characteristic directional specificity. There was no significant difference between the static and dynamic (alternating) conditions. Experiment 2 investigated the directional specificity of body sway found in Experiment 1 by having the trunk either be faced toward the stimulus display or perpendicularly to it, with the head always facing the display. The results showed that the stabilizing effect of peripheral vision was present in the direction of stimulus observation (i.e., the head/gaze direction), irrespective of trunk orientation. This suggested that head/gaze direction toward the stimulus presentation, rather than a biomechanical factor like greater mobility of the ankle joint in AP direction than in ML direction, was essential to postural stability. Experiment 3 further examined whether the stabilizing effect of peripheral vision found in Experiments 1 and 2 was caused because more dots (500) were presented as visual cues to the peripheral visual field than to the central visual field (20 dots) by presenting the same number of dots (20) in both conditions. It was found that, in spite of the equal number of dots, the postural sway amplitudes were larger for the central vision conditions than for the peripheral vision conditions. In conclusion, the present study showed that peripheral rather than central vision contributes to maintaining a stable standing posture, with postural sway being influenced more in the direction of stimulus observation, or head/gaze direction, than in the direction of trunk orientation, which suggests that peripheral vision operates primarily in a viewer-centered frame of reference characterized by the head/gaze direction rather than in a body-centered frame of reference characterized by the anatomical planes of the body.

Body Height↗

PubMed1982

Difference between eye closure and visual stabilization in the control of posture in man.

Stabilizing the visual surroundings of human subjects influences postural control during perturbations of their equilibrium. The latency of the first EMG burst is increased and its amplitude is reduced. Body pitch is 36% stronger than with normal vision. Eye closure does not produce any significant modification of muscular responses and postural performance. This result explains why vision is not considered a rapid source of postural reaction. Eye closure cannot be considered to be visual deprivation.

Electromyography↗

PubMed2004

A review of standing balance recovery from stroke.

Recently, interest in the mechanisms underlying balance recovery following stroke has grown, because insight into these mechanisms is necessary to develop effective rehabilitation strategies for different types of stroke. Studies dealing with the recovery of standing balance from stroke are, however, limited to rehabilitation inpatients with a unilateral supratentorial brain infarction or haemorrhage. In most of these patients, stance stability improves in both planes as well as the ability to compensate for external and internal body perturbations and to control posture voluntarily. Although there is evidence of true physiological recovery of paretic leg muscle functions in postural control, particularly during the first three months post-stroke, substantial balance recovery also occurs in patients when there are no clear signs of improved support functions or equilibrium reactions exerted through the paretic leg. This type of recovery probably takes much longer than 3 months. Apparently, mechanisms other than the restoration of paretic leg muscle functions may determine the standing balance recovery in patients after severe stroke. No information is available about the role of stepping responses as an alternative to equilibrium reactions for restoring the ability to maintain upright stance after stroke. The finding that brain lesions involving particularly the parieto-temporal junction are associated with poor postural control, suggests that normal sensory integration is critical for balance recovery. Despite a considerable number of intervention studies, no definitive conclusions can be drawn about the best approach to facilitate the natural recovery of standing balance following stroke.

Biofeedback, Psychology↗

PubMed1995

Optical flow, spatial orientation, and the control of posture in the elderly.

Stabliographic techniques were used to better understand the role of the visual system in the perceptual motor activity of older people as it relates to the maintenance of postural control. The central research question was to determine the sensitivity of the subject's visual system to changes in three standard conditions of optical flow generated by an experimental moving room. Any movement that was present as a function of this optical flow field was recorded on a force platform and expressed in movement of a computed center-of-pressure variable. Movement of the center of pressure was recorded in a baseline condition and in the experimental conditions, and the data were analyzed with respect to differences in the three conditions of optical flow and between both younger and older subjects. The older subject group exhibited less stability than the younger subjects in response to the baseline conditions; and, after adjusting for baseline movement, the center-of-pressure motions of younger and older subjects, in response to the experimental conditions, were compared. No reliable differences were present between younger and older subjects for the radial optical flow condition; in the lamellar flow condition, older subjects moved significantly more than younger subjects; and, in the combined condition (global), the movement of the older subjects was significantly greater than that of the younger subjects for all motion variables recorded. The results are interpreted and discussed both in terms of their implication for falling in the elderly and in the context of an ecological interpretation of the role of vision in maintaining postural stability while both stationary and in motion.

Accidental Falls↗

PubMed1976

[The study of control of posture by frequency analysis of surface electromyogram: an analysis of changes in muscular activity under the controlled posture (author's transl)].

In order to examine the function of muscle for control of posture a frequency analysis was performed of surface EMGs taken from the arm (M. deltoideus) held at the shoulder level. The results indicate that: (a) Power spectra first with a dominant especially with respect to 45-55 Hz component changed significantly 2 components of 5-60 Hz and 65-75 Hz when a 5 min experiment were repeated 3 times, and (b) the ratios of increased power was remarkable in both bands of 10-15 Hz and 30-35 Hz with repeating trials. The control of posture was discussed from the standpoint of behavioral psychology.

Adult↗

PubMed1993

Dynamic properties of feed back control of human posture in subjects with vestibular neuritis.

Postural control was studied in 22 subjects with vestibular neruitis within 14 days after the onset of symptoms. Dynamic feed back control of posture were evaluated by analyzing the postural responses to vibration toward calf muscles applied according to a PRBS schedule. Properties of the dynamic control was normalized as swiftness, stiffness and damping of the responses. There was no prominent group differences between the 22 subjects with vestibular neuritis and 17 normal subjects. However, when studying the change in parameters evoked by presence or absence of visual information it was found that the abundant changes of control parameters, especially in stiffness, met in normal subjects had declined in subjects with vestibular neuritis. The present finding suggests that although subjects after an acute vestibular lesion may achieve a sufficient postural control by utilizing information from other somatosensory receptors, this is concomitant with changes of the feed back control.

Adult↗

PubMed2003

Function of otolith organ in goldfish revealed from analysis of eye movement induced by acceleration.

An otolith organ on ground behave as a detector of both gravity and linear acceleration, and play an important role in controlling posture and eye movement for tilt of the head or translational motion. On the other hand, a gravitational acceleration ingredient to an otolith organ disappears in microgravity environment. However, linear acceleration can be received by otolith organ and produce a sensation that is different from that on Earth. It is suggested that in microgravity signal from the otolith organ may cause abnormality of posture control and eye movement. Therefore, the central nervous system may re-interprets all output from the otolith organ to indicate linear motion. A study of eye movement has been done a lot as one of a reflection related to an otolith organ system. In this study, we examined function of otolith organ in goldfish revealed from analysis of eye movement induced by linear acceleration or the tilt of body. We analyzed both torsional and vertical eye movements from video images frame by frame. For tilting stimulation, torsional eye movements induced by head down was larger than that induced by head up for larger tilt angle than 30 degrees. In the case of linear acceleration below 0.4 G, however, no clear differences were observed in both torsional and vertical eye movement. These results suggest that body tilt and linear acceleration may not be with equivalent stimulation to cause eye movement on the ground.

Acceleration↗

PubMed1987

Non-invasive estimation of afferent inputs for postural stability under low levels of alcohol.

The maintenance of human equilibrium is a complex process. Several physiological systems provide afferent information for postural stabilization. This study describes a noninvasive methodology to estimate the relative roles of interacting afferent inputs relevant for postural control. A multiaxis force platform in conjunction with specially designed test procedure provided semi-quantitative insight into the roles of vision, proprioceptors and vestibular apparatus in controlling postural sway when it was perturbed by a central nervous system perturbator such as alcohol. Experiments were conducted on 10 male and 10 female subjects. The males did not show statistically significant increases in body sway at these low levels of alcohol. For the females, the present methodology could detect subtle changes in postural sway at low blood alcohol levels ranging between 0.015% and 0.03%. At these low levels of alcohol, the results from females show that when the vision was excluded and the proprioception was modified, the postural sway was most affected. The postural instability experienced in this condition is probably due to inappropriate responses to proprioceptive inputs and lack of vision. Both male and female subjects showed a strong "eyes by standing surface" interaction. The proprioceptor manipulation alone did not affect the postural stability.

Adult↗

PubMed2004

Vestibulo-ocular reflex and gravity in fish.

An otolith organ on ground behave as a detector of both gravity and linear acceleration, and play an important role in controlling posture and eye movement for tilt of the head or translational motion. On the other hand, a gravitational acceleration ingredient to an otolith organ disappears in microgravity environment. However, linear acceleration can be received by otolith organ and produce a sensation that is different from that on Earth. It is suggested that in microgravity signal from the otolith organ may cause abnormality of posture control and eye movement. We examined function of otolith organ in goldfish revealed from analysis of eye movement induced by linear acceleration. We analyzed vertical eye movements from video images frame by frame. In normal fish, leftward lateral acceleration induced downward eye rotation in the left eye and upward eye rotation in the right eye. Acceleration from caudal to rostra1 evoked downward eye rotation in both eyes. When the direction of acceleration was shifted 15 degrees left, the responses in the left eye disappeared. These results suggested that otolith organs in each side transmitted different signals.

Acceleration↗

PubMed2006

The effect of positioning for children with cerebral palsy on upper-extremity function: a review of the evidence.

CONTEXT: Controversy exists about the most appropriate seating position for children with cerebral palsy (CP) to promote energy conservation and maximize upper-extremity function. EVIDENCE ACQUISITION: Sixteen journal articles published after 1980 were identified by searching allied health, medical, and occupational and physical therapy data bases and evidence-based medicine reviews using specific key terms (positioning, wheelchair, postural control, posture, adaptive seating devices, patient positioning, cerebral palsy, movement disorders, upper extremity, reaching, grasping, and occupational therapy) and reviewing bibliographies of retrieved articles. EVIDENCE SYNTHESIS: The majority of the evidence supports the positive effects of a neutral to slightly forward orientation (whole chair tilted) on upper-extremity function. Only one study did not demonstrate such effects. Of the supporting studies, one suggested the addition of an abduction orthrosis (AO), one recommended the entire functional sitting position (FSP) package (this orientation plus a hip-belt, footrests, AO, and cutout tray), and one established the long-term effects of the FSP. One less rigorous study opposed the addition of an AO. With the exception of one study, most of the evidence states that seat angle does not affect functional abilities. However, some of these studies contain faulty methodology and/or their results demonstrate clinical significance. CONCLUSION: Evidence supports that children with CP should be fitted for wheelchairs that place them in a FSP, which includes; orientation in space of 0 degrees -15 degrees, a hip-belt, an AO, footrests, and a cutout tray, with the addition of a sloped forward seat of 0 degrees -15 degrees, to improve upper-extremity function. The exact seat angle and orientation in space within the 0 degrees -15 degrees range should be determined on an individual basis.

Activities of Daily Living↗

PubMed2004

The importance of perceived relative motion in the control of posture.

Two experiments investigated the role of optic flow in controlling posture. Both experiments measured postural sway in two virtual environments with different 3-D structure but the same optic flow. Observers attempted to maintain balance on one foot while viewing an object that appeared either rigid with respect to the environment or that appeared to move concomitantly with head movements. The apparent object motion concomitant with head motion was achieved by changing the perceived, but not physical, depth of the object. For both objects, the optic flow information was the same and only depth information was varied. Observers showed a decrease in stability (as measured by head sway) when viewing the object that appeared to move, suggesting that perceived relative motion, not optic flow, signals self-motion to the postural control system.

Adult↗

PubMed1992

Recovery of postural equilibrium control following spaceflight.

Decreased postural stability is observed in most astronauts immediately following spaceflight. Because ataxia may present postflight operational hazards, it is important to determine the incidence of postural instability immediately following landing and the dynamics of recovery of normal postural equilibrium control. It is postulated that postflight postural instability results from in-flight adaptive changes in central nervous system (CNS) processing of sensory information from the visual, vestibular, and proprioceptive systems. The purpose of the present investigation was to determine the magnitude and time course of postflight recovery of postural equilibrium control and, hence, readaptation of CNS processing of sensory information. Thirteen crew members from six spaceflight missions were studied pre- and postflight using a modified commercial posturography system. Postural equilibrium control was found to be seriously disrupted immediately following spaceflight in all subjects. Readaptation to the terrestrial environment began immediately upon landing, proceeded rapidly for the first 10-12 hours, and then proceeded much more slowly for the subsequent 2-4 days until preflight stability levels were reachieved. It is concluded that the overall postflight recovery of postural stability follows a predictable time course.

Adult↗

PubMed1996

Visual control of posture during walking: functional specificity.

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 sway in 6 possible directions. With the wall, sway amplitude was isotropic and directionally specific in all conditions. However, with the hallways, sway was anisotropic (lateral > anterior-posterior [AP]), and diagonal responses were flattened into the lateral plane. When the treadmill was turned 90 degrees to the hallway, both the anisotropy and flattening were reversed (AP > lateral), indicating that they are determined by the visual structure of the scene. The results can be explained by postural control laws based on both optical expansion and motion parallax, yielding biases in planar environments that truncate parallax.

Adult↗

PubMed1976

Adapting reflexes controlling the human posture.

Doubt about the role of stretch reflexes in movement and posture control has remained in part because the questions of reflex "usefulness" and the postural "set" have not been adequately considered in the design of experimental paradigms. The intent of this study was to discover the stabilizing role of stretch reflexes acting upon the ankle musculature while human subjects performed stance tasks requiring several different postural "sets". Task specific differences of reflex function were investigated by experiments in which the role of stretch reflexes to stabilize sway doing stance could be altered to be useful, of no use, or inappropriate. Because the system has available a number of alternate inputs to posture (e.g., vestibular and visual), stretch reflex responses were in themselves not necessary to prevent a loss of balance. Nevertheless, 5 out of 12 subjects in this study used long-latency (120 msec) stretch reflexes to help reduce postural sway. Following an unexpected change in the usefulness of stretch reflexes, the 5 subjects progressively altered reflex gain during the succeeding 3-5 trials. Adaptive changes in gain were always in the sense to reduce sway, and therefore could be attenuating or facilitating the reflex response. Comparing subjects using the reflex with those not during so, stretch reflex control resulted in less swaying when the task conditions were unchanging. However, the 5 subjects using reflex controls oftentimes swayed more during the first 3-5 trials after a change, when inappropriate responses were elicited. Four patients with clinically diagnosed cerebellar deficits were studied briefly. Among the stance tasks, their performance was similar to normal in some and significantly poorer in others. Their most significant deficit appeared to be the inability to adapt long-latency reflex gain following changes in the stance task. The study concludes with a discussion of the role of stretch reflexes within a hierarchy of controls ranging from muscle stiffness up to centrally initiated responses.

Adaptation, Physiological↗

PubMed2002

Multisensory fusion: simultaneous re-weighting of vision and touch for the control of human posture.

We examined the generally held belief that the postural control system is able to re-weight its available sensory inputs in order to optimize stance control in altered sensory environments. Our view is that previous accounts of sensory re-weighting provide only indirect evidence, which is subject to alternative explanations. The present results provide strong evidence for sensory re-weighting as the primary mechanism for changes observed in postural sway between conditions. Subjects were presented with small-amplitude, oscillatory visual and somatosensory stimuli at 0.20 and 0.28 Hz, respectively, in five conditions that manipulated the amplitudes of stimulus motion. Gain calculated in each trial with respect to each of the two stimuli was found to change systematically as stimulus motion amplitudes changed across condition. The observed pattern of gain rules out a constant-weight, linear account of posture and is consistent with the re-weighting hypothesis. Parameter fits of a third-order, linear stochastic model to postural sway trajectories in each condition showed that changes in gain across condition were primarily due to changes in coupling coefficients rather than changes in parameters that characterize the stability of the postural system. Visual gain was found to depend upon visual motion amplitude and touch gain was found to depend upon touch motion amplitude, indicating intra-modality dependencies. Visual gain also depended upon touch motion amplitude, indicating an inter-modality dependence. To our knowledge, simultaneous re-weighting of more than one sensory input has never been rigorously demonstrated. These techniques may be able to resolve the source of balance control deficits across populations with far more certainty than currently possible.

Adult↗

PubMedDate not supplied

A method for evaluating vestibular control of posture.

Tests that measure the patient's ability to control his posture generally have failed to yield clinically useful information about vestibular function. The primary reason for this failure is that postural control does not depend on vestibular function when visual and proprioceptive cues are available. To test vestibular function, one should use a procedure that forces the patient to rely on vestibular cues by eliminating cues from these other sensory systems. Such a procedure is described. Vision is eliminated by eye closure, and proprioceptive cues are minimized by rotating the supporting surface to null changes in ankle angle. Data are presented which show that postural responses are complex, but that they appear to conform to the pattern originally observed by Nashner. A method potentially capable of separately evaluating semicircular canal and otolith function is described.

Ankle Joint↗

PubMed1997

Early recognition of postural disorders in multiple sclerosis through movement analysis: a modeling study.

In the present study, spontaneous postural behavior has been analyzed in freely standing multiple sclerosis (MS) patients, exhibiting no clinically assessable abnormalities of postural control. This population has been compared with two other groups, healthy people and hemiparetic patients. This latter group represents a situation where the central nervous system (CNS) lesion is precisely localized in one anatomical site and no signal-conduction disorders are present; i.e., it has an opposite anatomical character with respect to the MS at a preclinical stage. The hypothesis underlying the modeling study is the presence of a controller block working in a feedback posture control system. This controller block receives the body sway as input, and produces the corresponding ankle torque stabilizing the body, the latter being modeled as an inverted pendulum. The CNS damage, caused by MS, is supposed to be reflected in some detectable change in the structure of the controller of the posture control system. The identification of the controller has been performed by means of a parametric estimation procedure which employed as input sequences, data recorded by means of a movement-analysis (MA) system. Reported findings show a structural changes of the model of the controller block in the posture control system. This result may suggest the presence of an MS-specific reorganization of the posture control system. Some speculation is finally made on the black-box approach in comparison with traditional posturography, to arrive at hypothesizing a progression path for postural disorders.

Adult↗

PubMed2003

Effects of hypothermic anesthesia of the feet on vibration-induced body sway and adaptation.

The aim of this study was to investigate the significance of information from the plantar cutaneous mechanoreceptors in postural control and whether postural control could compensate for reduced cutaneous information by adaptation. Sixteen healthy subjects were tested with eyes open or eyes closed with hypothermic and normal feet temperature during posturography where body sway was induced by vibratory proprioceptive stimulation towards both calf muscles. The hypothermic anesthesia was obtained by cooling the subject's feet in ice water for 20 minutes. Body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface by a force platform during the posturography tests. The reduction of cutaneous sensor information from the mechanoreceptors of the feet significantly increased the vibration-induced torque variance mainly in the anteroposterior direction. However, the effects of disturbed mechanoreceptors information was rapidly compensated for through postural adaptation and torque variance was in level with that without anesthesia within 50 to 100 seconds of stimulation, both when standing with eyes open and eyes closed. Our findings suggest that somatosensory input from mechanoreceptors in the foot soles contribute significantly in maintaining postural control, but the sensory loss could be compensated for.

Adaptation, Physiological↗