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PubMed2005

Postural control after vestibular schwannoma resection measured with visual feedback posturography.

BACKGROUND: Vestibular symptoms after surgery diminish rapidly, but the simultaneous progress in active postural control has not been fully addressed. OBJECTIVES: The aim was to evaluate the progress in postural control in operated vestibular schwannoma (VS) patients with visual feedback posturography (VFP). METHODS: 36 consecutive patients with unilateral VS were studied with the VFP pre-operatively, 1 month and 3 months after the surgery. The accuracy and velocity of active postural control movements to distant targets in VFP was measured and compared to that of healthy controls. RESULTS: The hold percentage within the targets was significantly reduced in the VS patients compared to the controls (pre-operatively p = 0.005; postoperatively at 1 month p = 0.002 and at 3 months p = 0.017). The sway velocity (SV) within the targets among patients with VS was significantly increased pre-operatively (p = 0.009), at the 1-month (p = 0.004) and at the 3-month follow-up visits (p = 0.016). All the postural control parameters except SV tended to improve slightly postoperatively. The consecutive VFP measurements in individual VS patients correlated statistically significantly (p < 0.001 for all parameters). The abnormality in the pre-operative VFP results correlated statistically significantly with that of postoperative VFP (p = 0.001). CONCLUSIONS: The VFP is an objective and repeatable method, which can be used to assess and follow up the active postural control in individual patients with VS. Persisting abnormality in the VFP seems to be an indication for more aggressive vestibular rehabilitation to normalize the disturbed postural control.

Adult↗
PubMed1994

Differential sensitivity to static visual cues in the control of postural equilibrium in man.

Decreasing the visual sampling rate by reducing the stroboscopic frequency affected the postural performance of human subjects. At low strobe frequencies of up to 2 flashes/sec., at which only static visual cues were available, no decrease in subjects' mean postural sway was previously observed as compared to their equilibrium behavior without vision. In this experiment, to test the hypothesis that there may be a differential sensitivity to static visual cues in the control of postural equilibrium, we examined the possible effects of subjects' sex and previous sports training on this sensitivity. The static postural equilibrium abilities of 70 subjects of both sexes were tested in a sharpened Romberg position. Performance was measured with accelerometers within a vertical cylinder under normal illumination, 2-Hz stroboscopic light, and darkness. Comparisons between the average postural performances under 2-Hz strobe light and darkness showed no significant differences between conditions. Analysis of subjects' individual scores showed that 27% of the sample performed significantly better under the strobe light than in darkness, 57% produced similar performances under both conditions, and 16% performed better in darkness. Although significant differences existed between the postural performances of men and women and between trained and untrained subjects, no differences were observed in the differential sensitivity to static visual cues depending on subjects' sex or on previous physical training.

Adolescent↗
PubMed1978

Postural equilibrium in adolescent idiopathic scoliosis.

Postural equilibrium has been quantified by stabilometry in 57 patients with adolescent idiopathic scoliosis aged 10-16 years. Treatment was required in 39 cases whereof 18 were placed under observation only. The control group comprised 32 healthy children of the same age. An experimental design was made to vary the degree of difficulty of upright standing in four different test situations. The postural sway was analysed in the sagittal and lateral direction as well as in the area of total sway. The scoliotic patients had a significantly poorer postural control compared with the healthy children in all the tests. The difference was most pronounced in tests in which the proprioceptive functions were most important for maintaining the postural equilibrium. The left convex patients had quantitatively more pronounced reactions than the right convex patients. Patients with small curvatures, i.e., patients placed under observation only, had significantly increased postural sway compared with patients with more severe deformity. This fact, together with findings in patients with double primary curvatures, and the results of the study of brace effects, indirectly indicate the possibility of a postural disequilibrium as a contributory causative factor in adolescent idiopathic scoliosis.

Adolescent↗
PubMed2001

[Effects of 7 d -6 degrees bed-rest on postural equilibrium].

OBJECTIVE: To quantitatively assess the effects of 7 d -6 degrees head-down bed-rest (HDBR) on postural equilibrium and to investigate the contributions of vestibular, somatosensory and visual informations to postural equilibrium. METHOD: Eight healthy males, aged 33 - 42 years, were exposed to -6 degrees head-down tilt bed rest for 7 d. Sensory Organization Test (SOT) and Motor Coordination Test (MCT) were measured before and after HDBR, and day 4 of recovery. RESULT: Equilibrium scores of SOT in condition 1 (eyes opened, platform and visual scence environment fixed), 5 (eyes closed visual scence environment fixed, platform movable) were significantly lower as compared with pre-HDBR value, and recovered to pre-HDBR level on day 4 of recovery. Postural strategy scores of SOT in condition 1, 2 (eyes closed, platform and visual scence environment fixed) and 3 (eyes opened, platform fixed, visual scence environment movable) were significantly lower as compared with pre-HDBR value, and recovered to pre-HDBR level on day 4 of recovery. The dependence of somatosensory and visual information (ratio pair codition 2/condition 1, condition 3/condition 1 in sensory analysis) was significantly higher as compared with pre-HDBR value, and recovered on day 4 of recovery. Mean SOT alignment scores in conditions 1, 4 (eyes opened, visual scence environment fixed, platform movable) and 6 (eyes opened, platform and visual scence environment movable) were significantly higher as compared with pre-HDBR value, and only the scores of conditions 1, 6 were recovered on day 4 of recovery, but that of condition 4 did not. Mean postural-evoked response latencies of MCT were not significantly different as compared with pre-HDBR value. CONCLUSION: 7 d -6 degrees head-down tilt bed-rest has significant effects on postural equilibrium. The contributions of somatosensory and visual informations to postural equilibrium are increased.

Adult↗
PubMed2003

[Quantified research of measuring postural balance by posturography using inclinometer technique].

OBJECTIVE: To gain the normal values of posturography using inclinometer technique in people, to gain the normal values of posturography using inclinometer technique in people. METHOD: The messages of postural average sway angular velocity (omega) obtained by posturography using inclinometer technique in four various conditions were measured in 167 normal subjects who were grouped by age. RESULT: The normal omega values show that there is no correlation between postural balance with gender, but postural balance is related with age. The postural stability is at its best at the age of 20 to 60 years. The direction of postural sway has a large inter-individual variability, but no significant inclined direction is found. CONCLUSION: The results of individual tests should be compared with match-aged normative data in order to determine abnormal postural balance function. We measured many subjects and grouped by ages in detail. Therefore, the result can be taken as normative data of the measuring system. The omega value of standing on global-ottomed platform with eye closed could distinguish abnormal balance function of vestibo-spinal system accurately.

Adult↗
PubMed2004

[Clinical and stabilometric analysis of postural instability in Parkinson's disease].

A disturbance of postural control is one of the most invalidating symptoms of Parkinson's disease (PD), and mechanisms underlying its development have not been so far elucidated. To specify the postural control features in different PD forms, clinico-neurophysiological analysis was conducted in 61 patients divided into 3 groups according to PD forms: tremor-rigid, rigid-tremor and akinetic-rigid. Dissociation between clinical expression of postural instability and its stabilometric reflection--the square of statokinesogram was found, indicating importance of differentiated approach in performance of stabilometric analysis in patients with different PD forms. The square of statokinesogram may be regarded as a neurophysiological marker of postural instability only in patients with rigid forms, in tremor parkinsonian phenotypes an increased square of stabilogram being mainly a stabilometric reflection of tremor. The importance of stabilometric test performance with cognitive loading, allowing switching out of voluntary posture control, is shown. Possible neuromediator mechanisms involved in postural instability in PD are discussed.

Adult↗
PubMed2006

Postural adaptation in elderly patients with instability and risk of falling after balance training using a virtual-reality system.

Our aim in this study was to assess postural control adaptation quantitatively in unsteady elderly patients at risk of falls in open spaces and given balance training with a virtual-reality system reproducing environmental stimulation. Using a balance rehabilitation unit based on a virtual-reality system that changes sensory information (visual, vestibular, and somatosensory), we treated 26 elderly, unsteady patients who were prone to falling (age range, 73-82 years) and who were enrolled in a customized vestibular rehabilitation program. We assessed postural responses by posturography before and after 6 weeks in the vestibular rehabilitation program under two conditions: (1) standing, eyes open, static visual field, and (2) standing, eyes open, dynamic visual field through virtual-reality goggles, generating horizontal optokinetic stimulation (70 degrees per second angular velocity). We recorded postural responses with a platform measuring the confidential ellipse of the center-of-pressure distribution area and sway velocity with a scalogram analyzing postural behavior by wavelets. After 6 weeks of treatment, postural response confidential ellipse and sway velocity values were lower, evincing decreased amplitudes and sway frequency contents in the scalogram by wavelet under both stimulation paradigm conditions. These findings suggest postural adaptation under the two perceptual conditions when patients had static and dynamic visual fields. The possibility of treating elderly fallers with balance disorders using a virtual-reality environmental stimulation reproduction system is discussed.

Accidental Falls↗
PubMed1991

Human postural dynamics.

The study of posture dynamics is important not only to understand disorders of impaired equilibrium and protective reactions to unexpected displacements of the human body, but also to the design of prosthesis and functional neuromuscular stimulation as aids to patients with impaired postural stability and locomotion. Coordinated control of the body segments is a complex aspect of motor behavior, owing to the multiple degrees of freedom of the controlled system. Several interacting subsystems are involved in the dynamics of human posture and locomotion, including the skeletal, neuromuscular, and sensory systems. Human posture control is maintained by somatosensory, vestibular, and visual feedback, integrated within the locomotor and central nervous systems. Studies of posture dynamics and stability therefore entail the study of mechanical aspects of the human body, its sensory systems, and the principles governing coordination in motion control. In this paper is reviewed some of the research done in the field of human posture dynamics, including such topics as biomechanics, equilibrium, stability, motion coordination, neural feedback, neural control systems modeling, motion strategies, optimality of motion, and adaptation. We consider experimental approaches and theoretical models, as well as the gap between them. Principles for the experimental investigation of control systems are considered.

Animals↗
PubMed1984

Postural changes accompanying voluntary movements. Normal and pathological aspects.

Voluntary movements are the source of a perturbation of posture and equilibrium. They are accompanied by postural adjustments which show three main characteristics: they are "anticipatory" with respect to movement and minimize the perturbation of posture and equilibrium due to the movement; they are "adaptable" to the conditions in which the movement is executed, they are influenced by the instructions given to the subject concerning the task to be performed. The central organization of the postural adjustments associated with movement is still largely unknown. The possibility is examined that a "repertoire" of postural adjustments exists; the possible sites of the repertoire are discussed as well as the level at which the parallel or "sequential" control of posture and movement might be organized.

Adult↗
PubMedDate not supplied

Functional implications of postural disequilibrium due to lead exposure.

Measurement of postural equilibrium has been employed as an indirect indicator of functional status of the nervous systems of 109 children (mean age: 5.8 +/- 0.78 years) from the Cincinnati Lead Program Project. The geometric mean blood lead for the first five years of life (PbB05) was 11.9 +/- 1.5 micrograms/dL. Postural sway associated with upright balance was noninvasively quantitated with a microprocessor-based force platform and four tasks performed for 30 sec each by the subjects. A covariate-adjusted multiple regression analysis showed statistically significant associations between PbB05 and the postural sway for the task requiring primarily vestibular and/or proprioceptive systems input, implying potential functional impairment. These findings raised several new issues which are addressed here: (1) A dynamic task has been developed to further test the effect of perturbing those afferents' functional capabilities. (2) A method has been developed to quantitate the stability boundary of each subject to better characterize the limits of functionally-safe postural sway. (3) There is a need to perform the postural sway in a shorter duration than 30 sec so that children younger than five years of age can be tested for early identification of Pb-induced functional impairment of postural equilibrium.

Child↗
PubMed1993

Influence of expectation and arousal on center-of-pressure responses to transient postural perturbations.

Central modulation of postural responses to external perturbations appears to be a function of subject expectation, which in turn depends on: 1) prior experience within the testing paradigm, and 2) available information specific to the impending perturbation. Conceivably, the effects of expectation could be mediated, in part, through arousal-related mechanisms. This study investigated the influence of expectation of "postural threat" on center-of-pressure responses to transient translational platform perturbations in 23 healthy young males. The influence of prior experience was assessed first by performing a series of repeated trials using moderately large perturbations. The effect of providing specific prior information was then evaluated by administering small "low-threat" and large "high-threat" perturbations, with and without prior precued information about the perturbation magnitude. Also assessed were the associations between the postural responses and changes in arousal, the latter indicated by heart rate and skin conductance measures. The results showed that prior testing experience had a profound influence on postural strategy selection and execution, whereas the influence of precued prior information was rather more subtle. A tendency to lean forward prior to perturbation was influenced both by experience and prior information. Marked decreases in arousal occurred over the course of the earliest trials, and there was also some evidence that prior information affected arousal. Although causal relationships cannot be established, the results did show evidence of association between arousal and postural responses, suggesting that arousal could have affected postural strategy selection and execution.

Adult↗
PubMed1997

Postural orientation, equilibrium, and the spinal cord.

In summary, adequate control of postural orientation and equilibrium is a prerequisite for virtually all skilled motor acts, even those apparently simple tasks of standing and walking. In the cat, certain aspects of postural orientation appear to be organized at the spinal level. In contrast, postural equilibrium is not achieved by spinal circuits in isolation, but seems to require input from higher centers. The challenge is to identify those higher centers and the means by which they produce appropriate postural reactions for maintaining balance. If, indeed, postural equilibrium is a function of descending systems, then in the future, the amount of recovery of postural equilibrium after injury and/or treatment could provide a quantitative measure of the degree of sparing and/or re-establishment of functional connections between higher centers and the spinal cord.

Animals↗
PubMed1997

Effects of vestibular rehabilitation on postural control.

We evaluated the effects of vestibular rehabilitation on postural instability in 2 patients with unilateral and bilateral reduced vestibular function. Another patient with unilateral vestibular disorder was treated with drugs without vestibular rehabilitation. The outcome of postural control in these 3 patients was measured using an EquiTest. With this apparatus, improvement of postural stability and change of postural strategy were measured under the condition eyes closed and platform movement was dependent on the subject's anterior-posterior sway. The observations suggest that the vestibular rehabilitation had a positive effect not only on postural stability but also on postural strategy.

Adult↗
PubMed1991

The nature of head postures in congenital nystagmus.

We investigated the factors that determine the nature and extent of abnormal head postures in patients with congenital nystagmus. The head positions and eye movements of 16 patients were monitored while they adopted a variety of gaze positions. Five patients displayed a single head posture and four displayed multiple head postures. Six of the nine head postures matched the minimum intensity zone. The extent of the head posture was also found to be dictated by the velocity distribution of the slow phase, the nystagmus beat direction, and the neutral zone. Our results suggest that the surgical management of a head posture should not always be based only on the relocation of the minimum intensity zone to the primary gaze position.

Adolescent↗
PubMed2006

Efficacy of postural restriction in treating benign paroxysmal positional vertigo.

OBJECTIVE: To investigate the efficacy of postural restriction after canalith repositioning in treating benign paroxysmal positional vertigo (BPPV). DESIGN: Prospective trial of patients with postural restriction vs those without postural restriction after treatment. PATIENTS: Patients with classic BPPV and with BPPV without nystagmus were treated using the modified Epley canalith repositioning procedure. Patients were randomly separated into 2 groups. The first group was instructed to wear a cervical collar and to maintain an upright head position for 2 days. The second group had no motion restriction. After 5 days, the patients were followed up and evaluated using the Dix-Hallpike test. RESULTS: In the first group, 56 of 62 ears healed after the first maneuver, and the remaining ears healed after the second. In the second group, 45 of 57 ears healed after the first maneuver, 6 after the second, and 5 (with subsequent postural restriction) after the third (1 ear did not improve). Five patients in the first group and 3 patients in the second group had BPPV without nystagmus; all of these patients healed after a single maneuver. The difference between the 2 groups in the number of maneuvers required for treatment was statistically significant (P<.05). The number of patients who required a third maneuver was significantly higher in the second group (P<.05). CONCLUSIONS: Postural restriction enhances the therapeutic effect of canalith repositioning in the treatment of posterior semicircular canal BPPV. The long-term efficacy of postural restriction in preventing BPPV recurrence has not been demonstrated.

Adult↗
PubMed1998

Posture and support use of Old World monkeys (Cercopithecidae): the influence of foraging strategies, activity patterns, and the spatial distribution of preferred food items.

A common objective in field studies of positional behavior is to establish functional links between locomotion, body size, habitat use, foraging strategies, and maintenance activities. In contrast, there has been relatively little effort to examine posture in a similar, comparative context. Although various studies have shown that particular postures are employed in specific contexts, the theory which could provide the basis for understanding posture on a more general level has not been explicitly stated. This is particularly true for primates lacking specializations such as prehensile tails, claws for clinging, or adaptations for forelimb suspension. Consequently, there are few a priori reasons for predicting postural differences among generalized arboreal quadrupeds. Six sympatric cercopithecid monkeys were studied for 14 months in the Ivory Coast's Tai Forest to determine if more general relationships do exist between posture and other aspects of behavior. The results demonstrate that the postural diversity with these primates can, to varying degrees, be understood within the context of differences in the spatial distribution of preferred food items, activity patterns, support use, and foraging strategies.

Animals↗
PubMed2002

A prospective study of computer users: II. Postural risk factors for musculoskeletal symptoms and disorders.

BACKGROUND: Despite widespread recommendations regarding posture during computer use, associations between specific postures and musculoskeletal health are not well characterized. METHODS: Six hundred and thirty-two newly hired computer users were followed prospectively to evaluate associations between posture and neck or shoulder (N/S) and hand or arm (H/A) musculoskeletal symptoms and musculoskeletal disorders. Participants' postures were measured at entry and they reported symptoms on weekly diaries. Participants reporting symptoms were examined for specific disorders. Multivariate Cox regression models were used to estimate associations between postural variables and risk of symptoms and disorders, controlling for confounding variables. RESULTS: Keying with an inner elbow angle > 121 degrees, greater downward head tilt, and presence of armrests on the participants chair were associated with lower risk of N/S symptoms or N/S disorders. Keying with elbow height below the height of the "J" key and the presence of a telephone shoulder rest were associated with a greater risk of N/S symptoms or N/S disorders. Horizontal location of the "J" key > 12 cm from the edge of the desk was associated with a lower risk of H/A symptoms and H/A disorders. Use of a keyboard with the "J" key > 3.5 cm above the table surface, key activation force > 48 g, and radial wrist deviation of > 5 degrees while using a mouse was associated with a greater risk of H/A symptoms or H/A disorders. The number of hours keying/week was associated with H/A symptoms and disorders. CONCLUSIONS: The results suggest that the risk of musculoskeletal symptoms and musculoskeletal disorders may be reduced by encouraging specific seated postures.

Arm↗
PubMed2006

Asymmetries in postural control and locomotion in chimpanzees (Pan troglodytes).

Posture and locomotion are two of the most primitive and basic motor manifestations of an organism's behavior. Although the restrictions they impose on other motor functions are evident, few studies have considered the possibility of asymmetries in these behaviors in human and nonhuman primates, and how they might impact other asymmetries at higher functional levels. The aim of the current study was to explore in a group of 10 chimpanzees at the Madrid Zoo-Aquarium the degree of asymmetry in four behaviors related to locomotion (walking, ascending, descending, and brachiating) and four behaviors associated with posture (sitting, lying, hanging, and changing postures). Few subjects showed individual preferences, but significant trends in the group for some of the behaviors were found, including right-hand use when initiating quadruped walking, and left-hand use when descending and hanging. Some significant correlations also emerged: a negative one between walking and descending, and a positive one between walking and brachiating and between sitting and changing postures. No correlations were found between locomotor and postural modes. Although we cannot make generalizations on the population level at this time, these findings highlight the importance of considering postural and locomotion factors when studying motor asymmetries in primates.

Animals↗