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 775 records · Page 43Linked to original sources

PubMed2004

Effects of intensity and locus of painful stimulation on postural stability.

Stimulation of small diameter afferents can influence motor behavior. Little is known about how a prolonged painful stimulation of these small afferents may affect essential motor behavior such as the maintenance of an erect stance. The present study documents the effects of 10-s weak, moderate and extreme painful stimulations applied to the dorsum of the feet on the postural stability. Also, the moderate painful stimulation was applied to the metacarpal heads to determine if a painful stimulation to a limb not involved in the maintenance of the erect stance affects the postural control mechanisms. Increasing the intensity of the painful stimulation applied to the feet yielded larger postural oscillations whereas stimulation to the hands did not affect the control of posture. This suggests that the painful stimulation mainly affected the postural control mechanisms via sensorimotor processes rather than via cognitive resources related to the perception of pain.

Adult↗

PubMed1986

Simulation studies on the control of posture and movement in a multi-jointed limb.

Simulation studies were performed to evaluate the effectiveness of different control schemes in stabilizing a multi-jointed limb (human arm) in response to force perturbations. The mechanical properties of the arm were modeled as a linear visco-elastic system and the effectiveness of negative feedback of angular position and torque was evaluated. The effectiveness of a given amount of position feedback depended strongly on the initial position of the arm and on the perturbation, while torque feedback was much more consistently effective in damping the motion of the limb.

Animals↗

PubMed1978

Visual input: its importance in the control of postural sway.

A new and measurable parameter in the study of static equilibrium is described. Using a minicomputer, the locus of postural sway was measured during 1 minute periods in 144 volunteer subjects, including 105 control subjects and 39 persons with above-knee amputations. It was hypothesized that the above-knee amputee group had lost a relatively predictable degree of proprioception and kinesthetic sense. Vestibular mechanisms were normal and, therefore, constant in both groups. Using a simple arithmetic formula, the effect of such loss of proprioception was estimated by comparing the amputee group with the nonamputee group, while the contribution of visual input was estimated by comparing both groups with their eyes open and closed. Using this parameter, no clear age dependency was demonstrated. The mean locus of sway for the amputee group was the same as the nonamputee group with the eyes open. However, a comparison of the eyes open/eyes closed ratio in both groups demonstrated a significantly greater increase for the amputee group than for control subjects (p less than 0.001). In the future, mean locus of sway might provide a useful clinical method of measurement and the eyes open/eyes closed ratio might provide a simple and useful method to communicate the dependency upon vision in individual patients.

Adolescent↗

PubMed2001

[Skeletal configurations of cervical column during rest to motion transition: generalization that underlie the motor repertoire in rodents].

During forward locomotion, guinea pigs adopted a posture which, although different, was as stereotyped as at rest. The whole extent of the vertebral column was extended, parallel to the earth-horizontal plane. This result supports the hypothesis that, in mammals, gaze and postural control by the central nervous system would be simplified by the adoption of a limited number of skeletal configurations. They would be optimized for energy saving, biomechanical efficacy and limitation of the number of degrees of freedom of the skeletal apparatus. Transition between rest and forward locomotion displayed two prominent characteristics: the head was stabilized versus space throughout the whole transition and the modifications of the skeletal geometry were confined to the median plane and to two major articular regions. Such an organization revealed a fourth characteristic of the guinea pig postural control: the skeletal configurations retained by evolution would ensure that smooth transitions take place between rest and the various activities of its motor repertoire. Finally, our purely descriptive data shed new light on the architecture of the neuronal network which underlies the vestibular control of gaze and posture.

Animals↗

PubMed2003

Postural stability is altered by the stimulation of pain but not warm receptors in humans.

BACKGROUND: It is now recognized that large diameter myelinated afferents provide the primary source of lower limb proprioceptive information for maintaining an upright standing position. Small diameter afferents transmitting noxious stimuli, however, can also influence motor behaviors. Despite the possible influence of pain on motor behaviors, the effects of pain on the postural control system have not been well documented. METHODS: Two cutaneous heat stimulations (experiment 1: non-noxious 40 degrees C; experiment 2: noxious 45 degrees C) were applied bilaterally on the calves of the subject with two thermal grills to stimulate A delta and C warm receptors and nociceptors in order to examine their effects on postural stability. The non-noxious stimulation induced a gentle sensation of warmth and the noxious stimulation induced a perception of heat pain (visual analogue scores of 0 and 46 mm, respectively). For both experiments, ten healthy young adults were tested with and without heat stimulations of the lower limbs while standing upright on a force platform with eyes open, eyes closed and eyes closed with tendon co-vibration of tibialis anterior and triceps surae muscles. The center of pressure displacements were analyzed to examine how both stimulations affected the regulation of quiet standing and if the effects were exacerbated when vision was removed or ankle proprioception perturbed. RESULTS: The stimulation of the warm receptors (40 degrees C) did not induce any postural deterioration. With pain (45 degrees C), subjects showed a significant increase in standard deviation, range and mean velocity of postural oscillations as well as standard deviation of the center of pressure velocity. The effects of heat pain were exacerbated when subjects had both their eyes closed and ankle tendons vibrated (increased standard deviation of the center of pressure velocity and mean velocity of the center of pressure). CONCLUSIONS: A non-noxious stimulation (40 degrees C) of the small diameter afferents is not a sufficiently intense sensory stimulation to alter the control of posture. A painful stimulation (45 degrees C) of the skin thermoreceptors, however, yielded a deterioration of the postural control system. The observed deteriorating effects of the combined stimulation of nociceptors and Ia afferents (when ankle tendons were vibrated) could result from the convergence of these afferents at the spinal level. This could certainly lead to the hypothesis that individuals suffering from lower limb pain present alterations of the postural control mechanisms; especially populations already at risk of falling (for example, frail elderly) or populations suffering from concomitant lower limb pain and sensory deficits (for example, diabetic polyneuropathy).

Adult↗

PubMed2003

Control of posture with FES systems.

One of the major obstacles in restoration of functional FES supported standing in paraplegia is the lack of knowledge of a suitable control strategy. The main issue is how to integrate the purposeful actions of the non-paralysed upper body when interacting with the environment while standing, and the actions of the artificial FES control system supporting the paralyzed lower extremities. In this paper we provide a review of our approach to solving this question, which focuses on three inter-related areas: investigations of the basic mechanisms of functional postural responses in neurologically intact subjects; re-training of the residual sensory-motor activities of the upper body in paralyzed individuals; and development of closed-loop FES control systems for support of the paralyzed joints.

Algorithms↗

PubMed1999

Disruption of postural readaptation by inertial stimuli following space flight.

Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post-flight postural stability studies were compared with a larger (n = 34) study of astronauts returning from shuttle missions of similar duration. Results from both studies indicated that inadequate vestibular feedback was the most significant sensory deficit contributing to the postural instability observed post flight. For two of the four IML-1 astronauts, post-flight postural instability and rate of recovery toward their earth-normal performance matched the performance of the larger sample. However, post-flight postural control in one returning astronaut was substantially below mean performance. This individual, who was within normal limits with respect to postural control before the mission, indicated that recovery to pre-flight postural stability was also interrupted by a post-flight pitch plane rotation test. A similar, though less extreme departure from the mean recovery trajectory was present in another astronaut following the same post-flight rotation test. The pitch plane rotation stimuli included otolith stimuli in the form of both transient tangential and constant centripetal linear acceleration components. We inferred from these findings that adaptation on orbit and re-adaptation on earth involved a change in sensorimotor integration of vestibular signals most likely from the otolith organs.

Adaptation, Physiological↗

PubMed2003

Inverse relation between postural variability and difficulty of a concurrent short-term memory task.

We measured postural stability while participants simply stood or stood while performing a digit rehearsal task of varying levels of difficulty in order to examine the effects on postural control of concurrent short-term memory demands. The rehearsal task manipulation avoided factors that contaminate postural sway measurements, such as vocal articulation or visual fixation during posture data collection. When participants performed the more difficult digit tasks (longer digit strings), postural sway was reduced relative to when performing an easy version of the task (few digits). The results identified a complex relation between postural control and cognitive or attentional demands.

Analysis of Variance↗

PubMed2004

Can forced-use therapy be clinically applied after stroke? An exploratory randomized controlled trial.

OBJECTIVE: To determine the efficacy, safety, and compliance with forced-use therapy (FUT) applied without additional "shaping" therapy during the rehabilitation phase of stroke. DESIGN: Prospective, randomized controlled trial. SETTING: Tertiary mixed rehabilitation center. PARTICIPANTS: Consecutive sample of 30 inpatients or outpatients with first stroke showing minimal movement of the arm and hand. Subjects who scored below 26 on the Mini-Mental State Examination were excluded. Seven subjects either did not provide consent or withdrew from the study. The remaining subjects were randomized into the control group (n=13) and the FUT group (n=10). INTERVENTION: FUT involved wearing a thick constraint mitten on the sound arm for as many as 6 hours a day. MAIN OUTCOME MEASURES: The Chedoke McMaster Impairment Inventory for arm, hand, postural control, and shoulder pain; Action Research Arm Test; grip strength; and FIM instrument. RESULTS: FUT subjects experienced 20% more recovery of the arm than did control subjects and more recovery of postural control (P=.04). Men benefited most from the program, and there was a tendency for FUT subjects to have more shoulder pain. Compliance was related to cognitive status. CONCLUSIONS: FUT, without shaping therapy, appears to augment arm recovery, but a larger sample is required to confirm these findings. The FUT mitten was safe and well tolerated; however, more research is needed to determine the relation between FUT and hemiplegic shoulder pain.

Activities of Daily Living↗

PubMed2002

Postural balance in children with cerebral palsy.

Postural control deficits have been suggested to be a major component of gait disorders in cerebral palsy (CP). Standing balance was investigated in 23 ambulatory children and adolescents with spastic diplegic CP, ages 5 to 18 years, and compared with values of 92 children without disability, ages 5 to 18 years, while they stood on a force plate with eyes open or eyes closed. The measurements included center of pressure calculations of path length per second, average radial displacement, mean frequency of sway, and Brownian random motion measures of the short-term diffusion coefficient, and the long-term scaling exponent. In the majority of children with CP (14 of 23) all standing balance values were normal. However, approximately one-third of the children with CP (eight of 23) had abnormal values in at least two of the six center of pressure measures. Thus, mean values for path length, average radial displacement, and diffusion coefficient were higher for participants with CP compared with control individuals with eyes open and closed (p<0.05). Mean values for frequency of sway and the long-term scaling exponent were lower for participants with CP compared with control participants (p<0.05). Increased average radial displacement was the most common (nine of 23) postural control deficit. There was no increase in abnormal values with eyes closed compared with eyes open for participants with CP, indicating that most participants with CP had normal dependence on visual feedback to maintain balance. Identification of those children with impaired standing balance can delineate factors that contribute to the patient's gait disorder and help to guide treatment.

Adolescent↗

PubMed2004

Time course analysis of angular control of the body and head while rising from a chair.

OBJECTIVE: To use time course information to improve understanding of the vestibular contribution to postural control as one rises from a chair. MATERIAL AND METHODS: A total of 24 healthy controls and 42 patients with varying degrees of vestibular dysfunction were studied. The time course of the angular motion of the body and head when rising from a chair with eyes open and closed was evaluated. The delay between the onset of the motions of the body and head was compared between subject groups. We also investigated transition points from forward lean of the body to backward reversion and from backward tilt of the head to forward reversion. RESULTS: With regard to the onset of chair rise, we found a significant difference in the delay between head and body motion between healthy controls and subjects with bilaterally impaired vestibular deficiency only when the eyes were closed. The time between the transition points of the head and body was stable between these groups. CONCLUSION: The mechanisms controlling the onset of head and body movements differ between normal subjects and those with bilateral vestibular deficits. In the latter, the loss of a reference of gravity causes a decrease in feed-forward postural control, which is compensated for by a somato-sensory feedback mechanism. Visual input seems to provide an alternative reference of gravity.

Caloric Tests↗

PubMed1988

Presentation of a posturographic test with loading of the proprioceptive system.

Postural control is maintained by sensory feedback from visual, vestibular and somatosensory receptors. Recently several methods for evaluating postural control have been devised, utilizing an imposed perturbation. Most of these methods use stimuli which simultaneously affect more than one of the sensory feedback loops. In the present paper a posturographic technique is presented with specific loading of the proprioceptive system, using a computer controlled vibratory stimulus and computerized analysis of the results.

Central Nervous System Diseases↗

PubMed2004

Role of basal ganglia-brainstem systems in the control of postural muscle tone and locomotion.

This chapter argues that a basal ganglia-brainstem system throughout the mesopontine tegmentum contributes to an automatic control of movement that operates in conjunction with voluntary control processes. Activity of a muscle tone inhibitory system and the locomotion executing system can be steadily balanced by a net excitatory cortical input and a net inhibitory basal ganglia input to these systems. We further propose that dysfunction of the basal ganglia-brainstem system, together with that of the cortico-basal ganglia loop, underlies the pathogenesis of motor disturbances expressed in basal ganglia diseases.

Animals↗

PubMed1991

Normal gait is differentially influenced by the otoliths.

Postural control depends on the integration of vestibular, somatosensory and visual orientation signals. The otolith contribution to postural control is achieved by the integration of otolith inputs and peripheral afferent inputs involved in crossed reflex pathways. This study shows that a functional linkage between otolith signals and activity in lower limb muscles is detectable in normal human gait. The otolith input appears to dominate particularly the neck proprioceptive and gaze motor influences during normal gait. This is demonstrated by an increase of tibialis anterior muscle activity during retroflexion of the head/neck, leading to an increased stability and counteracting possible perturbations. It is also shown by decrease of coordination during the movement caused by larger displacement of the centre of gravity demonstrated in vector diagrams.

Biomechanical Phenomena↗

PubMed1986

M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 5. Postural responses following exposure to weightlessness.

The four science crewmembers of Spacelab-1 were tested for postural control before and after a 10 day mission in weightlessness. Previous reports have shown changes in astronaut postural behavior following a return to earth's 1-g field. This study was designed to identify changes in EMG latency and amplitudes that might explain the instabilities observed post-flight. Erect posture was tested by having the subject stand on a pneumatically driven posture platform which pitched rapidly and unexpectedly about the ankles causing dorsi- and plantarflexion. Electromyographic (EMG) activity from the tibialis anterior and the gastrocnemiussoleus muscles was measured during eyes open and eyes closed trials. The early (pre 500 ms) EMG response characteristics (latency, amplitude) in response to a disturbance in the posture of the subject were apparently unchanged by the 10 days of weightlessness. However, the late (post 500 ms) response showed higher amplitudes than was found pre-flight. General postural control was quantitatively measured pre- and post-flight by a "sharpened Romberg Rails test". This test showed decrements in standing stability with eyes closed for several days post-flight.

Adaptation, Physiological↗

PubMed1988

Neuromuscular patterns of stereotypic hindlimb behaviors in the first two postnatal months. III. Scratching and the paw-shake response in kittens.

Neuromuscular patterns of scratching and the paw-shake response were studied in normal kittens from birth to postnatal day 60. Onset of both behaviors coincided with the development of secure weight-bearing posture and occurred on postnatal day 21 for scratching and postnatal day 26 for paw shaking. At onset, cycle periods for scratching (5-6 Hz) and paw shaking (8-10 Hz) were similar to that for adult cats, and EMG patterns were adult-like. The scratch cycle consisted of reciprocal flexor and extensor bursts of equal duration, while the shake cycle consisted of coactive knee extensor and ankle flexor bursts alternately active with ankle extensor bursts. The lack of scratching and paw shaking during the first 3 postnatal weeks and the adult-like EMG patterns at onset are consistent with the hypothesis that pattern-generating circuits within lumbosacral segments are available early in development but inhibited by the rostral neuraxis until postural control is sufficient to accommodate the response. To eliminate rostral inputs, including descending input critical for postural control, kittens were spinalized at the T12 level, and onset of paw shaking was accelerated. In kittens spinalized at birth, paw-shake onset occurred on postnatal day 14, while in kittens spinalized on postnatal day 14, onset occurred 48 h after spinalization. In all spinal kittens, however, knee extensor activity was disrupted and not normal by postnatal day 60. Mature neuromuscular patterns for scratching and paw shaking are available at onset of the behavior during normal development. Spinalization hastens the onset of paw shaking but the normal neuromuscular synergy is disrupted as well as the temporal structure of the multi-cycle response. Disruptions following spinalization may be due to altered development of spinal pattern generators or aberrant feedback from atypical hindlimb motions due to a retardation of hindlimb growth and an alteration of muscle contractile properties in spinal kittens.

Age Factors↗

PubMed2003

Postural instability enhances motor responses to transcranial magnetic stimulation in humans.

Does the state of postural instability require a high hierarchical level of posture control? Electromyographic (EMG) activity of leg muscles was recorded during transcranial magnetic stimulation (TMS) of the motor cortex and electrical stimulation of the tibial nerve (H-reflex) in healthy subjects standing on a rigid floor and on a rocking platform. In the soleus muscle, TMS-evoked EMG responses increased considerably (2.2+/-1.1 times) when balancing on the rocking platform, whilst the H-reflex tended to decrease. The effect of support instability was specific to the muscles participating in the posture control. The results suggest that postural instability might change the state and the role of the motor cortex in equilibrium maintenance.

Adult↗

PubMed1989

Current concepts of the vestibular system reviewed: 2. Visual/vestibular interaction and spatial orientation.

The vestibular system contributes to the generation of conjugate eye movements, spatial orientation, and postural control. The functional connections of the vestibular end-organs and of the descending vestibulospinal pathways and their importance to postural control were reviewed in the previous paper by Keshner and Cohen (pp. 320-330). This paper reviews the ascending vestibular pathways, the visual/vestibular interactions, and the role of the vestibular system in oculomotor control and spatial orientation.

Eye Movements↗