[Gaze and posture. Influence of the direction of gaze in the control of posture].
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Adolescent↗
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Results for “Postural control”
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[Central mechanism of postural reflex. Part II. Role of neck afferents on control of posture and movement, and pathogenesis of traumatic cervical syndrome (author's transl)].
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Afferent Pathways↗
A method for the biocybernetic physiological investigation of postural motor control and its disorders in children.
On a biocybernetic basis, a method for the investigation of human postural motor control with optimal multifrequent binary test-signals is described. The examinations presented demonstrate that a comprehensive and quantitative characterization of normal postural motor control and its disorders is possible by means of this method in children. The examination time is short, the motor task used is simple, and the load is physiologically adequate and standardized.
Child↗
The effect of short-duration sub-maximal cycling on balance in single-limb stance in patients with anterior cruciate ligament injury: a cross-sectional study.
BACKGROUND: It has previously been shown that an anterior cruciate ligament (ACL) injury may lead to impaired postural control, and that the ability to maintain postural control is decreased by fatigue in healthy subjects. To our knowledge, no studies have reported the effect of fatigue on postural control in subjects with ACL injury. This study was aimed at examining the effect of fatigue on balance in single-limb stance in subjects with ACL injury, and to compare the effects, and the ability to maintain balance, with that of a control group of uninjured subjects. METHODS: Thirty-six patients with unilateral, non-operated, non-acute ACL injury, and 24 uninjured subjects were examined with stabilometry before (pre-exercise) and immediately after (post-exercise) short-duration, sub-maximal cycling. In addition, the post-exercise measurements were compared, to evaluate the instantaneous ability to maintain balance and any possible recovery. The amplitude and average speed of center of pressure movements were registered in the frontal and sagittal planes. The paired t-test was used for the intra-group comparisons, and the independent t-test for the inter-group comparisons, with Bonferroni correction for multiple comparisons. RESULTS: No differences were found in the effects of exercise between the patients and the controls. Analysis of the post-exercise measurements revealed greater effects or a tendency towards greater effects on the injured leg than in the control group. The average speed was lower among the patients than in the control group. CONCLUSIONS: The results of the present study showed no differences in the effects of exercise between the patients and the controls. However, the patients seemed to react differently regarding ability to maintain balance in single-limb stance directly after exercise than the control group. The lower average speed among the patients may be an expression of different neuromuscular adaptive strategies than in uninjured subjects.
Adolescent↗
Coupling of fingertip somatosensory information to head and body sway.
Light touch contact of a fingertip with a stationary surface can provide orientation information that enhances control of upright stance. Slight changes in contact force at the fingertip provide sensory cues about the direction of body sway, allowing attenuation of sway. In the present study, we asked to which extent somatosensory cues are part of the postural control system, that is, which sensory signal supports this coupling? We investigated postural control not only when the contact surface was stationary, but also when it was moving rhythmically (from 0.1 to 0.5 Hz). In doing so, we brought somatosensory cues from the hand into conflict with other parts of the postural control system. Our focus was the temporal relationship between body sway and the contact surface. Postural sway was highly coherent with contact surface motion. Head and body sway assumed the frequency of the moving contact surface at all test frequencies. To account for these results, a simple model was formulated by approximating the postural control system as a second-order linear dynamical system. The influence of the touch stimulus was captured as the difference between the velocity of the contact surface and the velocity of body sway, multiplied by a coupling constant. Comparison of empirical results (relative phase, coherence, and gain) with model predictions supports the hypothesis of coupling between body sway and touch cues through the velocity of the somatosensory stimulus at the fingertip. One subject, who perceived movement of the touch surface, demonstrated weaker coupling than other subjects, suggesting that cognitive mechanisms introduce flexibility into the postural control scheme.
Adult↗
Impairment of learning the voluntary control of posture in patients with cortical lesions of different locations: the cortical mechanisms of pose regulation.
The process of learning to produce voluntary changes in the position of the center of pressures using biological feedback was studied by stabilography in patients with hemipareses due to cerebrovascular lesions in the zone supplied by the middle cerebral artery. There were significant impairments to learning in all groups of patients, who had lesions in different sites, demonstrating that cortical mechanisms are involved in learning to control posture voluntarily. These studies showed that patients with lesions in the right hemisphere had rather greater deficits in performing the task than those with lesions in the left hemisphere. There were significant differences in the initial deficit in performing the task on the first day of training depending on the side of the lesion. All groups of patients differed from healthy subjects in that significant learning occurred only at the initial stages of training (the first five days). Learning at the initial stage in patients with concomitant lesions of the parietal-temporal area and with combined lesions with motor, premotor, and parietal-temporal involvement was significantly worse and the level of task performance at the end of the initial stage was significantly worse than in patient with local lesions of the motor cortex. The level of learning was independent of the severity of the motor deficit (paresis, spasticity), but was associated with the severity of impairment of the proprioceptive sense and the severity of disruption to the upright posture (asymmetry in the distribution of support pressures, amplitude of variation in the position of the center of pressures). The learning process had positive effects on the severity of motor impairment and on the asymmetry of the distribution of support pressures in the standing posture. Reorganization of posture during bodily movements occurred mainly because of impairment to the developed "non-use" stereotype of the paralyzed lower limb.
Biomechanical Phenomena↗
Computerized dynamic posturography: What have we learned from space?
Computerized dynamic posturography (CDP) has been under development since 1970. Several reviews summarize key basic and clinical research studies and outline important clinical uses of CDP along with research applications. This report summarizes new information about the otolith control of posture obtained from the study of astronauts. The dynamics of recovery of postural control upon return from orbital flight provide insight to the peripheral vestibular and central nervous system components of vestibular compensation. The dynamics of postural compensation should aid the clinician in the diagnosis and management of imbalance of vestibular origin.
Adaptation, Physiological↗
Vestibular ataxia following shuttle flights: effects of microgravity on otolith-mediated sensorimotor control of posture.
Orbital spaceflight exposes astronauts to an environment in which gravity is reduced to negligible magnitudes of 10(-3) to 10(-6) G. Upon insertion into earth orbit, the abrupt loss of the constant linear acceleration provided by gravity removes the otolith stimulus for vestibular sensation of vertical orientation constantly present on Earth. Since the central nervous system (CNS) assesses spatial orientation by simultaneously interpreting sensory inputs from the vestibular, visual, and proprioceptive systems, loss of the otolith-mediated vertical reference input results in an incorrect estimation of spatial orientation, which, in turn, causes a degradation in movement control. Over time, however, the CNS adapts to the loss of gravitational signals. Upon return to Earth, the vertical reference provided by gravitational stimulation of the otolith organ reappears. As a result, a period of CNS readaptation must occur upon return to terrestrial environment. Among the physiological changes observed during the postflight CNS readaptation period is a disruption of postural equilibrium control. Using a dynamic posturography system (modified NeuroCom EquiTest), 16 astronauts were tested at 60, 30, and 10 days preflight and retested at 1 to 5 hours, and 8 days postflight. All astronauts tested demonstrated decreased postural stability immediately upon return to Earth. The most dramatic increases in postural sway occurred during those sensory conditions in which both the visual and proprioceptive feedback information used for postural control were altered by the dynamic posturography system, requiring reliance primarily upon vestibular function for control of upright stance. Less marked but statistically significant increases in sway were observed under those conditions in which visual and foot support surface inputs alone were altered.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Kinematic analysis of the hip and trunk during bilateral stance on firm, foam, and multiaxial support surfaces.
OBJECTIVE: To differentiate hip and trunk motion during double-leg stance. DESIGN: Trunk and hip angular position variances were measured on different support surfaces with and without vision. BACKGROUND: Postural control results from motion about the hips and trunk during bilateral stance. While the hip joint has been studied extensively, information concerning relative amounts of hip and trunk motions during postural control is limited. METHODS: Trunk flexion/extension, trunk lateral flexion, right and left hip flexion/extension and abduction/adduction angular position variances were assessed in 14 normal subjects using an electromagnetic tracking system during bilateral stance on firm, foam, and multiaxial support surfaces with and without vision. RESULTS: Significantly greater amounts of motion occurred at all joints for the multiaxial-eyes closed condition compared to all other surface-vision conditions. No significant differences were found between any other surface-vision conditions. Within the multiaxial-eyes closed condition, right and left hip flexion/extension and abduction/adduction magnitudes were significantly greater than those of trunk flexion and lateral flexion, and left hip flexion/extension motion was significantly greater than that of the right hip. CONCLUSIONS: Postural control mechanisms involve similar amounts of motion at the hips and trunk, except for conditions under which a rigid base of support becomes unstable and vision is eliminated. RELEVANCE: These results suggest that the trunk and hips should be considered separately during kinematic analysis of postural control. This information may be useful in providing a more sensitive assessment of postural control to identify balance-related pathologies associated with stroke, concussion, and somatosensory deficits.
Abdomen↗
Proprioceptive weighting changes in persons with low back pain and elderly persons during upright standing.
The purpose of this study was to examine whether postural instability observed in persons with spinal pain and in elderly persons is due to changes in proprioception and postural control strategy. The upright posture of 20 young and 20 elderly persons, with and without spinal pain, was challenged by vibrating ankle muscles (i.e. tibialis anterior, triceps surae) or paraspinal muscles. Center of pressure displacement was recorded using a force plate. Persons with spinal pain were more sensitive to triceps surae vibration and less sensitive to paraspinal vibration than persons without spinal pain. Elderly persons were more sensitive to tibialis anterior vibration than young healthy persons. These results suggest that spinal pain and aging may lead to changes in postural control by refocusing proprioceptive sensitivity from the trunk to the ankles.
Adult↗
Bilateral subthalamic nucleus stimulation improves balance control in Parkinson's disease.
BACKGROUND: Parkinson's disease (PD), the most common basal ganglia degenerative disease, affects balance control, especially when patients change balance strategy during postural tasks. Bilateral chronic stimulation of the subthalamic nucleus (STN) is therapeutically useful in advanced PD, and reduces the motor signs of patients. Nevertheless, the effects of STN stimulation on postural control are still debatable. AIMS: To assess the impact of bilateral STN stimulation on balance control in PD and to determine how basal ganglia related sensorimotor modifications act on neurosensorial organisation of balance and motor postural programming. METHODS: Twelve subjects aged 45-70 years underwent unified Parkinson's disease rating scale motor (part III) clinical tests, static and dynamic posturography, including sensory organisation and adaptation tests, shortly before and six months after bilateral implantation of electrodes into the STN. RESULTS: The postoperative static test showed an improvement in postural control precision both in eyes open and eyes closed conditions. The dynamic test highlighted the decreased number of falls and the ability of the patients to develop more appropriate sensorimotor strategies when stimulated. The sensory organisation test showed an improvement of equilibrium score and, thus, a better resolution of sensorial conflicts. CONCLUSIONS: STN stimulation allowed a reduction in rigidity and therefore an improvement in the ability to use muscular proprioception as reliable information, resulting in vestibulo-proprioceptive conflict suppression. STN stimulation has a synergistic effect with levodopa for postural control. Accordingly, non-dopaminergic pathways could be involved in postural regulation and STN stimulation may influence the functioning of these pathways.
Aged↗
Biocybernetic investigations of pursuit and posture motor control--a strategy for a detailed characterization of movement disorders in brain-damaged children.
By means of a biocybernetic approach the pursuit and posture motor control of brain-damaged children with spastic hemiparesis and disturbed motor coordination of mild extent were investigated. The postural motor control system was loaded by pseudostochastic binary torque sequences applied to the wrist. The dynamics of this system were characterized on the basis of the parameters forearm displacement as well as surface-EMG of M. Biceps and Triceps (calculations of weight functions). The pursuit motor control was analyzed by a pursuit tracking method. By this way the motor capacity for fine and rough motor coordination, motor rhythm, motor adaptation, the maximal speed of movements and motor reaction time could be tested. Considering these results a characterization of movement control on different levels of motor regulation was possible (dynamics of muscular, spinal, and supraspinal components of motor control).
Brain Damage, Chronic↗
Is there a transfer of postural ability from specific to unspecific postures in elite gymnasts?
The purpose of this study was to investigate the transfer of postural ability by comparing the level of performance and postural control of elite gymnasts in postures specifically trained or not. Fifteen elite gymnasts were asked to stand as still as possible with eyes opened in three conditions: bipedal, unipedal and handstand. Surface and mean velocity of the centre of pressure motions were used to quantify respectively performance and postural control. A ranking was made for each parameter to determine the level of each subject. As a whole, the subject's level of postural performance and control in one condition was not correlated to the corresponded level in another condition. Therefore, postural ability of elite gymnasts in the handstand is not transferable to upright standing postures.
Adolescent↗
Vestibular control of skeletal geometry in the guinea pig: a problem of good trim?
Motor control of different segments of the body with multiple degrees of freedom appears to be coordinated by utilizing preferred axes of motor activity. This hypothesis may also be applied to vestibular control of posture. To explore this question we studied the anatomical relationship between the head and the cervical vertebral column by taking radiographs of the head-neck region in unrestrained alert guinea pigs. We determined that biomechanical constraints contribute to the stereotypical skeletal geometry observed in the resting animal and to a functional segmentation of the head-neck movement apparatus. Subsequent lesion studies of vestibular end organs with quantification of the resulting postural syndromes suggest that the functional segmentation of the cervical vertebral column corresponds to a functional partitioning of vestibular afferents. Our findings also indicate that the sensorimotor transformation mechanisms necessary to convert a given head velocity signal into the appropriate neck motor frame are already embedded in the networks provided by second-order vestibular neurons. Good trim of postural control will be the end result of an appropriate internal representation of the objective vertical.
Afferent Pathways↗
The perception of an optical flow projected on the ground surface.
In most experiments in which the importance of visual control on postural stability is studied, optical stimuli attached to vertical surfaces are used. Analyses of long-term standing readjustments generally involve back-and-forth movements of a visual scene or its projection on vertical circular screens. In a natural environment, however, visual information is largely available from the ground. The aim of the experiment reported was to assess the effect of a flow pattern simulating an open outdoor setting on motion perception and postural control. Subjects were presented with an optical texture projected onto the ground. Periods of motionless texture alternated with equivalent durations of unidirectional flows. The change of position of the subject's centre of gravity over time was recorded on a force platform. Results show that the direction of body sway corresponded with that of texture motion. Important aftereffects, as shown in linear vection experiments, were also observed. However, the latency of postural responses was much shorter than with prolonged unidirectional flows produced in other locations of the visual environment. The hypothesis of an ecological specificity of the flows perceived on the ground during terrestrial displacements is discussed.
Adult↗
Effect of mood state on anticipatory postural adjustments.
Static postural control has been demonstrated to link with psychological state. However, the effect of psychological state on dynamic postural control remains unclear. In this study, we examined the effect of mood state on anticipatory postural adjustment (APA), one of the most important functions for dynamic postural control. Fourteen healthy male subjects performed unilateral arm elevation tasks after completing a Profile of Mood States (POMS) questionnaire. Mood state measured by POMS and the latency or amplitude of the APA in the ventral muscles (rectus femoris, tibialis anterior) of the lower limb showed significant negative correlations. The correlation between the mood state and APA amplitude in the soleus was found to be significantly positive. There were significant negative correlations between the mood state and reaction-time. These findings suggest that it is possible that dynamic postural control is affected by mood state.
Adaptation, Physiological↗
Comparison of balance responses and motor patterns during sit-to-stand task with functional mobility in stroke patients.
This study was undertaken to explore whether we could provide supportive laboratory evidence for the clinical observations that a stroke patient has lost functional mobility/locomotion capability based on dynamic balance responses (center of force sway patterns) and motor control activities (electromyography patterns) during the motor task of sit-to-stand. A computerized controlled dynamic postural control assessment system was developed and used in this study. Various dynamic balance indexes were introduced and derived from center of force sway patterns expressed in four domains (space, time, force, and frequency). Motor control was assessed by multichannel surface electromyography of each side of the lower limb during the same motor task. The functional mobility capability was evaluated using the traditional FIM method. Fourteen stroke patients with right hemiplegia and nine healthy elderly individuals were recruited as the experimental and control groups, respectively. Muscle activity was recorded for quadriceps, hamstrings, anterior tibialis, and triceps surae muscles and was used for analysis. Center of force sway patterns and ground reaction forces were registered. All signals were synchronized at "seat-off." Surface electromyographic patterns of activities recorded during sit-to-stand and dynamic balance indexes computed from center of force sway patterns were categorized and compared with the functional mobility scores. Results show that both the motor control patterns and dynamic balance indexes correlated well to the extent of mobility impairment evaluated using the traditional FIM method. An important conclusion for rehabilitation medicine is that the functional mobility capability of stroke patients may be expressed numerically using dynamic balance indexes and visualized graphically through electromyographic motor patterns.
Adult↗
New quantitative and qualitative measures on functional mobility prediction for stroke patients.
The purpose of this study was to explore whether we could provide supportive laboratory evidence for clinical observations that a stroke patient has lost functional mobility/locomotion capability based on dynamic balance responses (centre of pressure, COP sway patterns) and motor control activities (EMG patterns) during the motor task of sit-to-stand. A computerized controlled dynamic postural control assessment system was developed and used in this study. Various dynamic balance indices were introduced and derived from COP sway patterns expressed in four domains (i.e. space, time, force, and frequency). Motor control was assessed by multi-channel surface electromyography of each side of the lower limb during the same motor task. The functional mobility capability was evaluated using a traditional FIM method. Fourteen stroke patients with right hemiplegia and nine healthy elderly were recruited as the experimental and control groups respectively. Muscle activity was recorded for quadriceps, hamstrings, anterior tibialis, and triceps surae muscles and used for analysis. Centre of pressure sway patterns and ground reaction forces were registered. All signals were synchronized at 'seat-off'. Surface electromyographic patterns of activities recorded during sit-to-stand and dynamic balance indices computed from centre of pressure sway patterns were categorized and compared with the functional mobility scores. The results show that both the motor control patterns and dynamic balance indices correlated well to the extent of mobility impairment evaluated using the traditional FIM method. An important conclusion for rehabilitation medicine is that the functional mobility capability of stroke patients may be quantified analytically using dynamic balance indices and visualized graphically through EMG motor patterns.
Activities of Daily Living↗