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At least 1,459 records · Page 81Linked to original sources
PubMed2002

Effect of pain reduction on postural sway, proprioception, and quadriceps strength in subjects with knee osteoarthritis.

OBJECTIVE: To investigate whether alleviation of knee pain influences quadriceps function, proprioceptive acuity, and postural stability in patients with knee osteoarthritis (OA). METHODS: A crossover, within-subject, double blind study design involving 68 subjects with painful knee OA. Each subject received an intra-articular injection into one or both knees (both if symptomatic) of either 5 ml 0.5% bupivacaine or 5 ml 0.9% saline. Two weeks later they received an injection of the alternative agent. Subjects and observer were unaware of the order of injection, which was randomly assigned. Knee pain (100 mm visual analogue scale), static postural sway, knee proprioceptive acuity, maximum voluntary contraction (MVC), and percentage activation of the quadriceps were assessed immediately before and one hour after each injection. RESULTS: Significant pain reduction was achieved one hour post-bupivacaine (mean difference as a percentage change 56.85, 95% CI 31.01 to 73.65; p<0.001) and post-saline (mean difference as a percentage change 41.94, 95% CI 11.57 to 76.66; p< 0.001), with no significant difference between the two. Both MVC and activation increased significantly post-bupivacaine (mean percentage differences 18.83, 95% CI -31.79 to -0.26, and -11.90, 95% CI -39.53 to 2.97, respectively; both p<0.001) and post-saline (mean percentage differences -7.64, 95% CI -21.96 to 4.73, and -10.71, 95% CI -25.19 to 2.60 respectively; both p<0.001). Proprioception worsened after bupivacaine (mean percentage difference -28.15%, 95% CI -83.47 to 19.74; p=0.009), but there was no effect on postural sway; saline injection had no effects. There was no order effect, and comparison of median percentage changes showed no significant differences between injections for change in MVC, activation, proprioception, or sway. CONCLUSION: Reduction in knee pain through either peripheral (local anaesthetic) or central (placebo) mechanisms resulted in increased MVC. This increase, however, did not result in improvements in proprioception or static postural stability, suggesting that other mechanisms play a part in these functions, at least in this acute model.

Adult↗
PubMed2003

Dynamic regulation of sensorimotor integration in human postural control.

Upright stance in humans is inherently unstable, requiring corrective action based on spatial-orientation information from sensory systems. One might logically predict that environments providing access to accurate orientation information from multiple sensory systems would facilitate postural stability. However, we show that, after a period in which access to accurate sensory information was reduced, the restoration of accurate information disrupted postural stability. In eyes-closed trials, proprioceptive information was altered by rotating the support surface in proportion to body sway (support surface "sway-referencing"). When the support surface returned to a level orientation, most subjects developed a transient 1-Hz body sway oscillation that differed significantly from the low-amplitude body sway typically observed during quiet stance. Additional experiments showed further enhancement of the 1-Hz oscillation when the surface transitioned from a sway-referenced to a reverse sway-referenced motion. Oscillatory behavior declined with repetition of trials, suggesting a learning effect. A simple negative feedback-control model of the postural control system predicted the occurrence of this 1-Hz oscillation in conditions where too much corrective torque is generated in proportion to body sway. Model simulations were used to distinguish between two alternative explanations for the excessive corrective torque generation. Simulation results favor an explanation based on the dynamic reweighting of sensory contributions to postural control rather than a load-compensation mechanism that scales torque in proportion to a fixed combination of sensory-orientation information.

Adaptation, Physiological↗
PubMed2004

Controlling human upright posture: velocity information is more accurate than position or acceleration.

The problem of how the nervous system fuses sensory information from multiple modalities for upright stance control remains largely unsolved. It is well established that the visual, vestibular, and somatosensory modalities provide position and rate (e.g., velocity, acceleration) information for estimation of body dynamics. However, it is unknown whether any particular property dominates when multisensory information is fused. Our recent stochastic analysis of postural sway during quiet stance suggested that sensory input provides more accurate information about the body's velocity than its position or acceleration. Here we tested this prediction by degrading major sources of velocity information through removal/attenuation of sensory information from vision and proprioception. Experimental measures of postural sway were compared with model predictions to determine whether sway behavior was indicative of a deficit in velocity information rather than position or acceleration information. Subjects stood with eyes closed on a support surface that was 1) fixed, 2) foam, or 3) sway-referenced. Six measures characterizing the stochastic structure of postural sway behaved in a manner consistent with model predictions of degraded velocity information. Results were inconsistent with the effect of degrading only position or acceleration information. These findings support the hypothesis that velocity information is the most accurate form of sensory information used to stabilize posture during quiet stance. Our results are consistent with the assumption that changes in sway behavior resulting from commonly used experimental manipulations (e.g., foam, sway-referencing, eyes closed) are primarily attributed to loss of accurate velocity information.

Acceleration↗
PubMed2005

Postural dysfunction in children with cerebral palsy: some implications for therapeutic guidance.

Postural problems play a central role in the motor dysfunction of children with cerebral palsy (CP). Therefore, they spend more time in sitting than in standing to perform vital tasks of daily life. The focus of this article is to describe the pathophysiology of postural control in sitting and outline some implications for management and treatment. In general, children with CP exhibit muscular activity counteracting forces that disturb equilibrium. Only 'non-sitting' children with severe CP lack such 'direction-specific' adjustments, possibly ruling out achievement of independent sitting. Most frequently, the children display dysfunctions in the adaptation of the adjustment. Typical characteristics of this adaptation in children with CP are a top-down recruitment of postural muscles, an excessive degree of antagonistic coactivation, and an incomplete adaptation of the EMG-amplitude to task specific constraints. Despite our knowledge on the pathophysiology underlying the postural problems in children with CP, little 'high-level' evidence (according to Sackett) exists on how different interventions can affect these problems. Therapeutic attention to promote motor performance in sitting focuses on adaptive seating, tilting of the support surface, and ample, variable training in motivating settings. The challenge facing us now is to provide evidence about the efficacy of specific treatment approaches facilitating that children reach an optimal level of functioning in daily life.

Cerebral Palsy↗
PubMedDate not supplied

Visual contributions to postural stability in older adults.

BACKGROUND: With advancing age, there is a generalized reduction in visual functioning which has been associated with impaired postural stability and increased risk of falls. However, little is known about which visual abilities are the most important in the control of postural sway when standing. OBJECTIVE: To determine whether specific visual abilities predict stability when standing on firm and compliant surfaces. METHODS: Tests of visual function, peripheral sensation, strength, reaction time and sway were administered to 156 community-dwelling men and women aged 63-90 years. The visual tests included high- and low-contrast visual acuity, contrast sensitivity, depth perception, stereopsis and lower visual field size. Postural sway was measured with eyes open on a firm and a compliant foam rubber surface. RESULTS: On the firm surface, sway was significantly associated with only one sensorimotor measure: proprioception in the lower limbs. In contrast, on the compliant surface, sway was associated with all of the visual measures, quadriceps strength and reaction time. Multiple regression analysis revealed that contrast sensitivity, stereopsis and quadriceps strength were significant independent predictors of total sway when subjects stood on the compliant surface. CONCLUSION: The study findings confirm the importance of vision, in particular contrast sensitivity and stereopsis, in the control of posture under challenging conditions, and suggest some mechanisms for the association between impaired vision and falls in older people.

Accidental Falls↗
PubMedDate not supplied

Postural control measured by visual feedback posturography.

The objective was to study the applicability and repeatability of visual feedback posturography (VFP) in assessing postural control of 23 healthy subjects. The subjects had to move their center of gravity (COG) marker on a computer screen to chosen targets by leaning their body on the platform, and the accuracy, velocity, and side difference of these movements were measured. The intraclass correlation coefficients for all parameters during repeated tests were significant (r = 0.93 - 0.96; p < 0.01). Hold percentage within the targets and COG marker velocity to the targets did not change significantly during repeated tests. Balance index and hit delay were significantly smaller during the 4th and 5th than during the 1st test session (p < 0.05), but they did not change significantly between the other test sessions. The normative limit for side difference in postural control was 22%. VFP can be used to follow active postural control due to its high test-retest repeatability. However, learning effects in some parameters must be taken into account when applying VFP repeatedly in different patient populations to assess the progress in postural control.

Adolescent↗
PubMed2006

Preoperative postural control of patients with vestibular schwannoma assessed by visual feedback posturography.

BACKGROUND: The need for an objective method to describe the functional postural control of patients with vestibular schwannoma in agreement with their subjective sensation of balance. OBJECTIVES: The objective was to compare the postural control of 49 patients with unilateral vestibular schwannoma (VS) with that of healthy subjects by using visual feedback posturography (VFP). We aimed to find out if preoperative postural control of the patients correlates with their subjective sensation of balance. METHODS: In the VFP, while standing on the platform, patients were instructed to move their center of gravity (COG) marker to the targets as fast and accurately as possible. Hit delay (HD) to the targets, hold percentage (HP) within the targets, COG marker velocity (CMV) to the targets, and balance index (BI) were calculated. We rated intensity of balance disturbance using a 5-point qualitative scale. RESULTS: Twenty-two (45%) patients had at least one abnormal VFP parameter, and 49% of patients were simultaneously symptomatic. Mean hit delay (HD), hold percentage (HP), and balance index (BI) were significantly worsened in patients with VS (p < 0.05). Increased HD and BI correlated significantly with subjective sensation of imbalance (p = 0.02). CONCLUSIONS: The overall deficit in preoperative postural control of the VS patients was not severe, and this finding agreed well with their subjective sensations.

Adult↗
PubMed1991

Tullio phenomenon and postural stability: experimental study in normal subjects and patients with vertigo.

The effect of low-frequency sound (LFS) on postural stability was studied in 55 healthy volunteers and in 152 patients with vertigo due to different types of inner ear disease. The sound pressure levels ranged from 130 to 132 dB and were given at frequencies of 25, 50, and 63 Hz. The duration of each stimulation lasted 30 seconds. The postural responses were measured with a force platform. The LFS stimulation improved the postural stability of the healthy subjects through the alerting response. We did not observe any difference in the body sway according to whether the LFS was delivered with monaural or binaural stimulation. Twenty-six percent of the patients with Meniere's disease, 40% with chronic otitis media with vertigo, and 26% with vertigo of peripheral origin experienced significant postural instability at least at two of the three test frequencies during stimulation with LFS. The results demonstrate that in subjects with different types of inner ear disease the vestibular system starts to respond to LFS. The activation of vestibulospinal responses by LFS seems to be an expression of the Tullio phenomenon.

Acoustic Stimulation↗
PubMed2004

Underdevelopment of the postural control system in autism.

OBJECTIVE: To determine if abnormalities exist in postural control in autism and if they are related to age. METHODS: Dynamic posturography was performed in 79 autistic individuals without mental retardation and 61 healthy volunteers between ages 5 and 52 years. Both the sensory organization and the movement coordination portions of the test were performed. RESULTS: The autistic subjects had reduced postural stability (p = 0.002). Examination of age effects revealed that the development of postural stability was delayed in the autistic subjects (p < 0.001) and failed to achieve adult levels (p = 0.004). Postural stability was reduced under all conditions but was clinically significant only when somatosensory input was disrupted alone or in combination with other sensory challenges (mean reduction in stability of 2.6 +/- 1.0 for the first three conditions without somatosensory disruption vs 6.7 +/- 2.7 for the last three conditions with somatosensory disruption), indicating problems with multimodality sensory integration. CONCLUSIONS: The evidence from this and studies of the motor system suggests more general involvement of neural circuitry beyond the neural systems for social behavior, communication, and reasoning, all of which share a high demand on neural integration of information.

Adolescent↗
PubMed2003

Assessment of postural stability following sport-related concussion.

Despite the increased amount of research being conducted in the area of sport-related concussion, there is still a limited understanding regarding its effect on the injured brain's ability to control motor functions and coordination. This review determines the efficacy of postural stability testing as an adjunct to concussion assessment of athletes. Multiple studies, using both sophisticated force plate technology, as well as those using less sophisticated clinical balance tests, have identified postural stability deficits lasting several days following sport-related concussion. It appears that postural stability testing provides a useful tool for objectively assessing the motor domain of neurologic functioning, and should be considered a reliable and valid adjunct to the assessment of athletes suffering from concussion. Although symptom severity, neurocognitive function, and postural stability are often affected initially following concussion, they are not necessarily related or even affected to the same degree. Each of these should be considered when attempting to make return-to-play decisions following concussion.

Ataxia↗
PubMed2001

Effects of malathion on survival, growth, development, and equilibrium posture of bullfrog tadpoles (Rana catesbeiana).

Bullfrog (Rana catesbeiana) tadpoles were exposed to malathion in water in a 28-d static renewal test. The effects of malathion on survival, growth, development, and loss of equilibrium posture were determined. Survival was significantly decreased at malathion concentrations of 2,500 micrograms/L and higher. Development of tadpoles was delayed significantly by malathion exposure as indicated by a dose-related decrease in developmental stage over time. Development of tadpoles in the 1,000-microgram/L and higher treatment groups was significantly delayed from that observed in the control. The effects of malathion on developmental stage suggest that malathion may decrease thyroid function in tadpoles, as it does in other species. Maintenance of equilibrium posture following agitation of the test containers was significantly impaired in tadpoles in all the malathion treatment groups (500 to 3,000 micrograms/L) relative to the control. Maintenance of equilibrium posture was thus the most sensitive end point measured in this study. Loss of equilibrium posture could increase predation losses and decrease feeding in populations of bullfrog tadpoles in the field. However, concentrations of malathion that produced adverse effects in our study are higher than published, measured concentrations found in wetlands or streams.

Animals↗
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↗
PubMed1995

Vestibular plasticity following orbital spaceflight: recovery from postflight postural instability.

Results of previous studies suggested that the vestibular mediated postural instability observed in astronauts upon return to earth from orbital spaceflight may be exacerbated by an increased weighting of visual inputs for spatial orientation and control of movement. This study was performed to better understand the roles of visual and somatosensory contributions to recovery of normal sensori-motor postural control in returning astronauts. Preflight and postflight, 23 astronaut volunteers were presented randomly with three trials of six sensory organization test (SOT) conditions in the EquiTest system test battery. Sagittal plane center-of-gravity (COG) excursions computed from ground reaction forces were significantly higher on landing day than preflight for those test conditions presenting sway-referenced visual and/or somatosensory orientation cues. The ratio of summed peak-to-peak COG sway amplitudes on the two sway-referenced vision tests (SOTs 3 + 6) compared to the two eyes closed tests (SOTs 2 + 5) was increased on landing day, indicating an increased reliance on visual orientation cues for postural control. The ratio of peak-to-peak COG excursions on sway-referenced surfaces (SOTs 4, 5 & 6) to an earth fixed support surfaces (SOTs 1, 2 & 3) increased even more after landing suggesting primary reliance on somatosensory orientation cues for recovery of postflight postural stability. Readaptation to sway-referenced support surfaces took longer than readaptation to sway-referenced vision. The increased reliance on visual and somatosensory inputs disappeared in all astronauts 4-8 days following return to earth.

Astronauts↗
PubMed1979

Vestibulospinal reflex activity in patients with adolescent idiopathic scoliosis. Postural effects during caloric labyrinthine stimulation recorded by stabilometry.

Postural sway has been quantified with stabilometry during caloric labyrinthine stimulation in an erect posture in 49 patients, aged 10--16 years, with adolescent idiopathic scoliosis. Thirty-two healthy children of the same age constituted a control group. The scoliotic patients tended to have an increased postural sway during labyrinthine stimulation on the convex side compared to the effects on the concave side. Significant differences were observed when left and right scoliotic patients were compared with the controls. The results can be explained by an asymmetric sensitivity in the labyrinth or by a dysfunction in the postural control mechanisms at the brain stem level.

Adolescent↗
PubMed2004

Reciprocal influences of attentional focus on postural and suprapostural task performance.

The authors examined the influence that attentional focus on either a postural or a suprapostural task had on the performance of each task. Participants (N = 32) stood on an inflated rubber disk and held a pole horizontally. All participants performed under 4 attentional focus conditions: external (disk) or internal (feet) focus on the postural task, and external (pole) or internal (hands) focus on the suprapostural task. Compared with internal focuses, external focuses on either task resulted in similar and reduced postural sway. Response frequency on each task increased when participants focused on the respective task. Finally, an external focus on either task produced higher frequencies of responding on the suprapostural task. The authors conclude that suprapostural task goals have a stronger influence on postural control than vice versa, reflecting the propensity of the motor system to optimize control processes on the basis of the desired movement effect.

Attention↗
PubMed1996

Haptic cues for orientation and postural control in sighted and blind individuals.

Haptic cues from fingertip contact with a stable surface attenuate body sway in subjects even when the contact forces are too small to provide physical support of the body. We investigated how haptic cues derived from contact of a cane with a stationary surface at low force levels aids postural control in sighted and congenitally blind individuals. Five sighted (eyes closed) and five congenitally blind subjects maintained a tandem Romberg stance in five conditions: (1) no cane; (2,3) touch contact (< 2 N of applied force) while holding the cane in a vertical or slanted orientation; and (4,5) force contact (as much force as desired) in the vertical and slanted orientations. Touch contact of a cane at force levels below those necessary to provide significant physical stabilization was as effective as force contact in reducing postural sway in all subjects, compared to the no-cane condition. A slanted cane was far more effective in reducing postural sway than was a perpendicular cane. Cane use also decreased head displacement of sighted subjects far more than that of blind subjects. These results suggest that head movement control is linked to postural control through gaze stabilization reflexes in sighted subjects; such reflexes are absent in congenitally blind individuals and may account for their higher levels of head displacement.

Adult↗
PubMed2001

Effects of prefabricated foot orthoses and soft insoles on postural stability in professional soccer players.

Postural stability is an important component of skilled athletic activity. However, the effects of foot orthoses on stability have not been adequately addressed. This study measured postural sway in 30 asymptomatic professional soccer players in three standing positions and four underfoot conditions. The results revealed that the underfoot condition had no significant effect on sway in the mediolateral or anteroposterior planes; however, there was a trend toward less mediolateral sway when subjects stood in a unipedal position with prefabricated orthoses. These results suggest that insoles and foot orthoses have no significant beneficial or detrimental effects on postural stability in asymptomatic subjects. Clinically, this suggests that no improvements in balance performance could be expected with prophylactic use of insoles or orthoses but that clinicians may prescribe insoles and foot orthoses without fear of impairing postural performance in elite athletes.

Adult↗
PubMed2000

The effects of Tai Chi Chuan on postural stability in the elderly: preliminary report.

BACKGROUND: Tai chi chuan (TCC) is a traditional Chinese conditioning exercise, consisting of a series of graceful movements linked together in a continuous sequence so that the body is constantly shifting from one foot to the other. We propose that subjects practicing TCC will have better postural control and stability than will active non-practitioners. METHODS: We compare static and dynamic postural controls in 14 TCC practitioners and 14 healthy active older adults using the Smart Balance Master System. The TCC group, containing 7 male and 7 female subjects (mean age, 70.9 +/- 3.3 years), had been practicing TCC regularly for 2 to 35 years. The control group included 4 male and 10 female healthy and active older subjects (mean age, 69.1 +/- 3.1 years), with age and body size matched to the TCC group. RESULTS: The results of static postural control tests showed no differences between the TCC and control groups under simple conditions (eyes open, eyes closed, swaying vision, and eyes open with swaying surface), but in the more complicated conditions (eyes closed with sway-referenced support and sway-referenced vision and support), the TCC group had significantly better results than the control group. In the dynamic balance test, the TCC group had significantly better results only in the rhythmic forward-backward weight-shifting test. CONCLUSION: Our data demonstrate that regular TCC practitioners have better postural stability, especially in the more complicated conditions with disturbed visual and somatosensory conditions.

Aged↗