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PubMed2006

Task demand effects on postural control in older adults.

The literature shows conflicting results regarding older adults' (OA) postural control performance. Differing task demands amongst scientific studies may contribute to such ambiguous results. Therefore, the purpose of this study was to examine the performance of postural control in older adults and the relationship between visual information and body sway as a function of task demands. Old and young adults (YA) maintained an upright stance on different bases of support (normal, tandem and reduced), both with and without vision, and both with and without room movement. In the more demanding tasks, the older adults displayed greater body sway than the younger adults and older adults were more influenced by the manipulation of the visual information due to the room movement. However, in the normal support condition, the influence of the moving room was similar for the two groups. These results suggest that task demand is an important aspect to consider when examining postural control in older adults.

Acclimatization↗

PubMed1992

Postural control in children with autism.

Postural control was evaluated in samples of autistic, normal, and mentally retarded children in this pilot study using a recently developed, computerized posturographic procedure. A battery of postural positions was administered including postures involving some degree of "stress" (e.g., occluded vision or standing on pads). The postural patterns of children with autism differed from those observed in normal children, in mentally retarded children, and in adults with vestibular disorders. In comparison to normal children the autistic subjects were less likely to exhibit age-related changes in postural performance and postures were more variable and less stable with more lateral sway. Autistic subjects also exhibited a "paradoxical" response of greater stability with more "stressful" postures, putting excessive weight on one foot, one toe, or one heel. The implications for neuroanatomical models of autism are discussed.

Autistic Disorder↗

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↗

PubMed1994

Vestibular disturbance at frequencies above 1 Hz affects human postural control.

The effect of primary vestibular disturbance on postural control was investigated in 11 normal subjects exposed to perturbation by bi-polar binaural galvanic stimulation of the vestibular nerve. The stimulus consisted of 30 s of sinusoidal galvanic stimulation at a frequencies of 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0 Hz, with a current of +/- 1 mA, the subject standing with open or closed eyes, the response evoked being recorded with a force platform. As compared with resting values, i.e. no stimuli, variance of lateral body sway was significantly greater at all frequencies tested in the closed eyes condition and at frequencies of 0.2, 0.5, 1.0, 3.0 and 4.0 Hz in the open eyes condition; using a high pass filter with a cut-off frequency of 0.1 Hz, variance of lateral body sway was significantly greater at frequencies 0.2, 0.3, 0.5, 1.0 and 2.0 Hz in the closed eyes condition and at frequencies 0.5 and 2.0 Hz in the open eyes condition. These findings suggest that in the lateral plane vestibular input affects and probably contributes to human postural control over a wider frequency range than suggested by findings in previous studies. The trends in sagittal body sway were similar. Moreover, the visual contribution appears to enable the subject to suppress vestibular input causing lateral body sway only in the lower frequency range (here at 0.2 and 0.3 Hz), but with regard to the concomitant sagittal body sway at a much wider range of frequencies (here at all frequencies tested except 1.5 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2001

Postural control: visual and cognitive manipulations.

Numerous questions exist regarding the utilization of sensory information for postural control. Past research has established the possibility that cognitive tasks requiring visual perception may affect the processing of visual information used for postural control. The purpose of this study was two fold: (1) to investigate the effects of varying demands of visual perception and (2) to evaluate the effects of performing a cognitive task on postural control in healthy, young adults (N=30). Three posture-related dependent variables were recorded during the manipulation of two independent variables (eye movement and modality of presentation of a cognitive task). The two levels of eye movement were movement and no movement, while the three levels of modality of presentation were visual, auditory, and none. A 2x3 repeated measures ANOVA was applied to the data to investigate the presence of group differences. Significantly more variability was observed in the no cognitive condition than the visual and the auditory for medial-lateral (M--L) COP variability. Additionally, the eye movement condition revealed significantly greater M--L COP variability than the no eye movement condition. No differences were observed between the visual and auditory conditions for any dependent variable. Therefore, the greatest COP variability was observed in the eye movement and no cognitive condition. Further, an interesting relationship between the measures of COP variability and sway velocity was described.

Adult↗

PubMed2000

Renormalization group analysis of a quivering string model of posture control.

Scaling concepts and renormalization group methods are applied to a simple linear model of human posture control consisting of a trembling or quivering string subject to damping and restoring forces. The string is driven by uncorrelated white Gaussian noise, intended to model the corrections of the physiological control system. We find that adding a weak quadratic nonlinearity to the posture control model opens up a rich and complicated phase space (representing the dynamics) with various nontrivial fixed points and basins of attraction. The transition from diffusive to saturated regimes of the linear model is understood as a crossover phenomenon, and the robustness of the linear model with respect to weak nonlinearities is confirmed. Correlations in posture fluctuations are obtained in both time and space domains. There is an attractive fixed point identified with falling. The scaling of the correlations in the front-back displacement, which can be measured in the laboratory, is predicted for both large-separation (along the string) and long-time regimes of posture control.

Humans↗

PubMedDate not supplied

The effects of visual surround eccentricity and size on manual and postural control.

This study investigated how the size and eccentricity of a moving visual surround influence manual and postural control. Twelve subjects performed a manual control task (keep an unstable central display level) and a postural control task (maintain an upright stance) while viewing a visual surround that rotated continuously at 25 degrees C/s. The visual surround consisted of small red squares on a dark background and was presented in four different size/eccentricity conditions: central (approximately 15 degrees C - 60 degrees C), peripheral (approximately 60 degrees C-110 degrees C), full-field (15 degrees C-110 degrees C), or central-peripheral conflict. The results showed that manual control biases in the direction of surround motion are strongly influenced by central-field as well as peripheral-field motion, whereas postural control biases are determined primarily by motion in the peripheral visual field.

Adult↗

PubMed2000

The influence of postural control on motility and hand function in a group of 'high risk' preterm infants at 1 year of age.

The functional outcome of a group of 75 'high-risk' preterm infants was studied at the corrected age of 12 months. Only infants with high-risk for developmental deviance with gestational ages below 32 weeks and/or birthweights less than 1500 g were included in the study. Additionally the infants were categorised according to their medical history conforming with the 'Neonatal Medical Index' (NMI I to V), with category I describing infants with few medical problems and V characterizing those with the most serious complications. In this study we included only infants with 'high-risk' as categorised in NMI III to V, since infants with 'low-risk' have been described earlier. Infants with cerebral ultrasonographic abnormalities were incorporated into the NMI categories, but also analysed separately to compare outcomes. At 12 months (corrected age) apart from pediatric follow-up, a full neurological assessment was done with emphasis on postural control, spontaneous motility and hand function. Special attention was given to symmetrical development. The infants were then categorised as having optimal, non-optimal or asymmetrical outcomes. An overall optimal outcome on postural control was found in 64% of all infants (67% in NMI III, 60% in NMI IV and 62.5% in NMI V). Too much extension interfering with postural control was found significantly more often in infants in NMI V (15%), compared to infants in NMI IV (8%) and NMI III (4.5%). Poor postural control had a significant influence on other domains of development such as motility (P=0.00), asymmetry (P=0.00) and hand function (P=0.00). Cerebral ultrasonographic abnormalities seemed to have an influence on motility (P=0.03), while no direct relationship was found with postural control, hand function or asymmetry. It is unclear whether this poor coordination of gross motor function will have consequences for appropriate visual-motor and sensorimotor integration therewith hampering later cognitive function, as often described in preterm infants. It is suggested that the poor postural control found in many infants is the result of both myogenic and/or neurogenic deviations and associated with cerebral pathology, but is also caused by the preterm birth and its nursing consequences.

Echoencephalography↗

PubMedDate not supplied

Recovery of postural control after cerebral concussion: new insights using approximate entropy.

CONTEXT: The return-to-play decision after sport-related cerebral concussion depends in part on knowing when an athlete has fully recovered postural control after injury. OBJECTIVE: To describe the postconcussion recovery of postural control using approximate entropy (ApEn), a regularity statistic from nonlinear dynamics. DESIGN: Retrospective case series analysis. SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS: Collegiate athletes from whom center-of-pressure and symptom data were collected at preseason, less than 48 hours after injury, and 48 to 96 hours after injury. MAIN OUTCOME MEASURE(S): Approximate entropy values reflecting the amount of randomness contained in center-of-pressure oscillations were calculated for anterior-posterior (AP) and medial-lateral (ML) time series. Equilibrium scores reflecting the amplitude of center-of-pressure AP oscillations were used to indicate postural stability. The number and severity of symptoms were described. RESULTS: Compared with the healthy preseason state, ApEn values for the AP and ML time series generally declined immediately after injury in both steady and unsteady injured athletes. At 48 to 96 hours after injury, ApEn values for the ML time series remained significantly depressed (mean difference compared with preseason = -0.268, standard error = 0.072), even among athletes whose initial postural instability had resolved. We found few significant relationships between changes in ApEn values and changes in symptoms before and after injury. CONCLUSIONS: The effects of cerebral concussion on postural control appear to persist for longer than 3 to 4 days, even among athletes with no signs of unsteadiness. Our results may reflect changes in neurophysiologic or mechanical constraints on postural control. Approximate entropy provides a theoretically distinct, valuable measurement alternative that may prove useful for reducing uncertainty in the return-to-play decision.

Journal Article↗

PubMed2006

Age-related part taken by attentional cognitive processes in standing postural control in a dual-task context.

The aim of this work was to determine the effects of ageing on the possible mobilisation of cognitive processes in orthostatic postural balance. Seventy-nine individuals of three different age groups were placed in dual-task situations that combined standing postural control with three different cognitive tasks. Two of these three tasks, auditory-verbal and visual-verbal ones, required external information acquisition whereas the third, a mental counting task, did not require such information. The results showed contrasting variations in postural control performances that are an improvement in young subjects during cognitive tasks which required external information acquisition and a deterioration in elderly subjects during cognitive tasks which did not involve external information acquisition. The middle-aged subjects tended to develop these two types of variations simultaneously. These results confirm that cognitive processes could have a role that increases with age in ensuring postural control. The contrasting results observed between the young and old populations highlight that the allocation of cognitive resources to postural control could, on the one hand, contribute to improving postural performance in subjects with mainly automated control and, on the other, perturb this performance in subjects with mainly cognitive control.

Adult↗

PubMed1997

Variations in foot breadth: effect on aspects of postural control during one-leg stance.

OBJECTIVE: To test the hypothesis that changing body weight toward the narrower rearfoot or the wider forefoot causes a decrease or increase in the amount of center of pressure (CoP) displacement per unit of foot tilt (EQ), and to examine the effect on postural control. DESIGN: Experimental, within-subject design with one controlled variable. SETTING: A biomechanics laboratory of a university department of biomedical physics and technology. SUBJECTS: Ten healthy, young subjects. MAIN OUTCOME MEASURES: The sagittal plane position of the CoP (Y) reflecting foot loading, EQ, and horizontal ground reaction forces (Fx) representing postural control. RESULTS: Shifting body weight to the rearfoot or forefoot decreases (d) or increases (i) Y (Pd = .002, Pi = .000) and EQ (Pd = .018, Pi = .064). In both cases Fx (Pd = .008, Pi = .098) increased and postural control deteriorated. CONCLUSIONS: Shifting body weight to the rearfoot or forefoot decreases or increases EQ. Besides the changes in EQ encountered here, other factors are held responsible for the deterioration of postural control. The absence or presence of changes in Y can be used to exclude or include the presence of an effect of EQ or these unknown factors on postural control.

Adult↗

PubMedDate not supplied

Significance of pressor input from the human feet in anterior-posterior postural control. The effect of hypothermia on vibration-induced body-sway.

The importance to postural control of the mechanoreceptors of the soles was investigated in thirteen healthy subjects. Body-sway velocity was evaluated before and after exposing the subject's feet to hypothermia, and when calf muscles were exposed to vibration at frequencies between 20 and 100 Hz. Subjects were tested both with eyes open and closed. Body-sway velocity was found to increase significantly during hypothermia of the feet. The difference in body-sway between hypothermal and normothermal conditions was less prominent when the subject's eyes were open though the difference was significant in both cases. The present results indicate the importance of the mechanoreceptors of the soles to postural control and elucidate their interaction with compensatory visual input in maintaining postural control. These findings also suggest, that factors affecting pressor input should be taken into consideration when assessing patients with complaints of dysequilibrium.

Adult↗

PubMed2004

[Voluntary postural control learning with a use of visual bio-feedback in patients with spinocerebellar degenerations].

The study aimed at evaluation of possibility and features of voluntary postural control learning using biofeedback from a force platform in patients with spinocerebellar ataxias. Thirty-seven patients with different forms of spinocerebellar degenerations and 13 age-matched healthy subjects were trained to shift the center of pressure (CP) during several stabilographic computer games which tested an ability to learn 2 different types of voluntary postural control: general strategy and precise coordination of CP shifting. Despite the disturbances of static posture and ability for voluntary control of CP position, patients with spinocerebellar degenerations can learn to control a vertical posture using biofeedback on stabilogram. In contrast to healthy subjects, improvement of coordination in the training process does not exert a significant influence on the static posture characteristics, in particular on lateral CP oscillations. The results obtained suggest involvement of the cerebellum in both types of postural control that distinguishes them from pathology caused by motor cortex and nigro-striatal system involved only in one type of postural control.

Adolescent↗

PubMed2001

Changes in postural control in healthy elderly subjects are related to vibration sensation, vision and vestibular asymmetry.

The aim of this study was to analyze the composition of sway in adults and "healthy" elderly people and to evaluate the influence of vibration sensation and asymmetric vestibular function on the sway pattern. Ten adults with a mean age of 37.5 years and 40 healthy senior citizens with a mean age of 74.6 years living independently in the community were studied. Vibration-induced body sway was measured on a force platform. The sway was analyzed and separated into its high and low frequency components above and below 0.1 Hz, respectively. Additionally the elderly subjects were observed for the occurrence of spontaneous gaze and head shake-induced nystagmus using infrared charge-coupled device cameras and the vibration perception in the lower limbs was tested with a tuning fork. Vibration perception was the major determinant for postural control in the elderly subjects. Postural control among the elderly subjects with intact vibration perception in their lower limbs was very similar to that of the adults. The elderly subjects with impaired vibration sensation had increased high frequency sway compared to adults and the elderly subjects with intact sensation. Regardless of the strong influence of vibration sensation on postural control, asymmetric vestibular function might also be a contributing factor to postural instability in the elderly. Age per se had little effect on the outcome of the tests except that the elderly subjects had diminished ability to use visual cues to reduce postural sway. We concluded that sensory status in the lower limbs is of utmost importance for postural control in the elderly. Rehabilitation programs for senior citizens should therefore include exercises to preserve recognition of body motion by the lower limbs. Exercises to facilitate vestibular compensation could be useful for elderly people with vestibular dysfunction.

Adult↗

PubMed2001

Postural control and cognitive task performance in healthy participants while balancing on different support-surface configurations.

Postural control during normal upright stance in humans is a well-learned task. Hence, it has often been argued that it requires very little attention. However, many studies have recently shown that postural control is modified when a cognitive task is executed simultaneously especially in the elderly and in the presence of pathology. This study examined postural control modifications when a cognitive task of varying difficulty levels is added. Postural stance difficulty was also varied. Results from this study suggest that a generalized capacity interference may occur due to the larger interference found with the addition of a cognitive task in the more novel and difficult postural task. Because the performance of the cognitive task was tapered by a speed-difficulty trade-off, it was not possible to determine whether a change in the level of difficulty of the cognitive task occurred and if it would produce larger dual-task interference.

Adult↗

PubMedDate not supplied

Significance of pressor input from the human feet in lateral postural control. The effect of hypothermia on galvanically induced body-sway.

The significance to human postural control of pressor information from the feet was investigated during vestibular disturbance in seven normal subjects who were exposed to bipolar biaural galvanic stimulation of the vestibular nerves before and after their feet were anaesthetized with hypothermia. The increase in body sway in the lateral plane induced by the galvanic stimulus was enhanced when the feet were anaesthetized, and adaptation of postural control to the galvanic stimulus was delayed. It is concluded that pressor information from the feet contributes significantly to postural control in humans and is important in compensating for vestibular disturbance.

Adaptation, Physiological↗

PubMed2000

Unique postural control of upside-down swimming catfish, Synodontis nigriventris, not affected by the change of gravity.

In general, most fishes maintain a swimming posture with the dorsal side towards the water surface under normal gravity condition. In contrast to normal fishes, a catfish Synodontis nigriventris, shows a unique postural control. The catfish keeps its posture with the ventral side towards the water surface and the dorsal side towards water bottom under normal gravity. This evidence leads one to assume that the upside-down posture of the catfish is controlled by gravity sensation in a manner different from that of other fishes. However, it has remained unclear to date whether the gravity sensation contributes to the unique postural control of this catfish. We examined its postural control in intact and labyrinth-removed catfish using a clinostat which generates a specific gravity environment (pseudo-microgravity) on earth. In addition, we examined its postural control under microgravity during parabolic flights.

Animals↗

PubMed1989

Age related decline in postural control mechanisms.

In order to study voluntary and reflexive mechanisms of postural control, young and elderly persons were given large-fast and small-slow ankle-rotation postural disturbances while standing on a movable platform capable of measuring ground reaction forces. Large-fast rotations were employed to activate long-loop reflexes, and small-slow rotations were employed to tap the higher level sensory integration aspects of postural control. Overall, the elderly persons exhibited more perturbation induced sway and showed a slowing in voluntary, as opposed to reflexive mechanisms of correcting postural disturbance. For both age groups, reflexive mechanisms were found to be relatively intact. When small perturbations were given, the elderly persons swayed more than young participants and produced sporadic reflexive activity. Moreover, elderly persons did not adapt to the small perturbations and exhibited increased postural sway to repetitive presentation of the perturbation, whereas young participants substantially decreased their postural sway. These data demonstrate that elderly persons are at some disadvantage when posture is under the control of slower, higher level sensory integrative mechanisms.

Adult↗