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PubMed2000

Balance control and posture differences in the anxious BALB/cByJ mice compared to the non anxious C57BL/6J mice.

A relation between anxiety disorders and balance control dysfunctions has been observed in many studies in humans. A mismatch in the integration of sensory inputs could trigger these disturbances. Very few experimental animal procedures have been designed to study the functional link between anxiety and balance control. A task was therefore developed, challenging the visual, vestibular and somesthesic sensory systems in mice. The test, called the 'rotating beam', gave an accurate assessment of balance control and the posture, using sensitive measures (number of falls and imbalances, position of tail and trunk). Striking differences were observed between the two inbred strains of mice known to have radically different anxiety-related behaviour. The highly anxious strain, BALB/cByJ, performed poorly compared to the non anxious strain, C57BL/6J. Balance control and postural abilities of anxious mice were improved by acute anxiolytic diazepam treatment. Lower behavioural performance level was registered in non anxious mice given anxiogenic beta-CCM treatment. The findings account for a strong relationship between anxiety and balance control in mice. Finally, the highly sensitive procedure proved to be well suited to the study of functional links between anxiety and sensorimotor processes.

Animals↗
PubMed1998

Posture and locomotion in the rat: independent or interdependent development?

In this essay, recent research into the relation between postural control and the development of walking in the rat is reviewed. The adult-like walking pattern develops at the 15th to 16th day (P15-P16). Until this age, postural control, as indicated by EMG activity in the longissimus muscle in the trunk, is poorly phased in relation to the stepcycle. After P15-P16, accuracy increases but only after P21 is the adult pattern of EMG activity in the trunk muscles in relation to locomotor activity in the hindpaw muscles established. Neuroanatomical research revealed that those muscles in trunk and extremities which fulfil important postural tasks are innervated by motoneuronal pools containing conspicuous dendrite bundles. These bundles emerge at about the age when the adult type of postural control starts to develop. As spinal transsection at P10 abolishes their development, we hypothesize that the development of dendrite bundles is dependent on the ingrowth or the becoming functional of descending projections. On the basis of the neurophysiological and neuroanatomical results we conclude that the development of postural control, which reaches its final stage 5-6 days after the adult-like pattern of walking has developed, is dependent on the maturation of suprasegmental structures and their spinal projections.

Adult↗
PubMed2002

Attention and the control of posture and gait: a review of an emerging area of research.

Research on the relationship between attention and the control of posture and gait is a new and expanding area with studies on young adults revealing the role of cognitive factors in the control of balance during standing and walking. The use of dual task paradigms to examine the effect of age related changes in attentional requirements of balance control and age-related reductions in stability when performing a secondary task has shown that these are important contributors to instability in both healthy and balance-impaired older adults. The attentional demands of balance control vary depending on the complexity of the task and the type of secondary task being performed. New clinical assessment methods incorporating dual-task paradigms are helpful in revealing the effect of disease (e.g. Parkinson's disease) on the ability to allocate attention to postural tasks and appear to be sensitive measures in both predicting fall risk and in documenting recovery of stability.

Accidental Falls↗
PubMed2005

Balance performance with a cognitive task: a dual-task testing paradigm.

PURPOSE: Athletic performance demands simultaneous use of cognitive and postural control capabilities. Decrements to both systems have been observed following concussion. This study evaluated a dual-task methodology to establish the tenability of using this testing model in concussed athletes. METHODS: Nonconcussed subjects were assessed over 2 d. Subjects were introduced to the task-switching cognitive assessment test and a NeuroCom Smart Balance Master postural control assessment protocol on day 1. In the following session, subjects were evaluated on postural control and cognitive function tests independently (single task), and then concurrently (dual task). RESULTS: Significant improvements were seen in three of the four balance conditions and in three of the four reaction times when the cognitive and balance task were performed simultaneously (P<0.05). No significant balance by cognitive task interaction was revealed (P>0.05); however, significant differences existed in reaction time based on stimulus position and increasing balance demands (P<0.05). CONCLUSION: Combining the cognitive and balance assessments resulted in healthy subjects showing improved performance when compared with individual task performance. The dual-task methodology brought about systematic changes to reaction time in relation to increasing balance demands. The ability of this protocol to detect changes in postural control or cognitive function following concussive injury requires further study.

Adult↗
PubMedDate not supplied

[Features of learning voluntary control of posture after pyramidal and nigrostriatal lesions].

The study was aimed at investigation of a deficit of learning the center-of-pressure voluntary control in patients with lesions of corticospinal and nigrostriatal systems. Thirty three patients with Parkinson's disease and 20 patients with hemiparesis after cerebrovascular accidents in the MCA participated in the investigation. The subjects stood on a force platform and in the form of a computer game were trained to match the projection of the center of pressure (a cursor) with a target on the screen under the visual feedback control. Two different postural tasks were presented. In the first task the direction of the center-of-pressure shift was not known before, so the subject learned the general strategy of the center-pressure control. In the other task a precise postural coordination should be formed. The voluntary control of the center-of-pressure position was found to be impaired in both groups of patients. In the task of moving the center of pressure in various directions (general strategy), no differences in the initial deficit of the task performance were found between the groups, but the learning was more efficient in the group of hemiparetic patients. However, in the task with precise postural coordination, despite the greater initial deficit in the parkinsonian patients, the learning in this group of patients was substantially more efficient than in hemiparetic patients. The results suggest both common and different features of the involvement of the corticospinal and nigrostriatal systems in learning voluntary control of posture.

Aged↗
PubMed2004

A new postural balance control system for rehabilitation training based on virtual cycling.

A new rehabilitation training system was developed to improve postural balance control by combining virtual reality technology with an unfixed bicycle. Twenty healthy subjects participated in the present study by riding the virtual cycling system under two different conditions: with or without visual feedback. Data were collected on the following parameters: path deviation, cycling velocity, etc. As a result of conducting the repeated training, results showed improvement not only in the ability to control balance and weight shift but also in the overall cycling ability including the degree of path deviation and the cycling speed. It was concluded that the system was effective as a training device and, in addition, the technology might have a wider applicability to the rehabilitation field.

Adult↗
PubMed2005

Comparing internal models of the dynamics of the visual environment.

It is well known that the human postural control system responds to motion of the visual scene, but the implicit assumptions it makes about the visual environment and what quantities, if any, it estimates about the visual environment are unknown. This study compares the behavior of four models of the human postural control system to experimental data. Three include internal models that estimate the state of the visual environment, implicitly assuming its dynamics to be that of a linear stochastic process (respectively, a random walk, a general first-order process, and a general second-order process). In each case, all of the coefficients that describe the process are estimated by an adaptive scheme based on maximum likelihood. The fourth model does not estimate the state of the visual environment. It adjusts sensory weights to minimize the mean square of the control signal without making any specific assumptions about the dynamic properties of the environmental motion. We find that both having an internal model of the visual environment and its type make a significant difference in how the postural system responds to motion of the visual scene. Notably, the second-order process model outperforms the human postural system in its response to sinusoidal stimulation. Specifically, the second-order process model can correctly identify the frequency of the stimulus and completely compensate so that the motion of the visual scene has no effect on sway. In this case the postural control system extracts the same information from the visual modality as it does when the visual scene is stationary. The fourth model that does not simulate the motion of the visual environment is the only one that reproduces the experimentally observed result that, across different frequencies of sinusoidal stimulation, the gain with respect to the stimulus drops as the amplitude of the stimulus increases but the phase remains roughly constant. Our results suggest that the human postural control system does not estimate the state of the visual environment to respond to sinusoidal stimuli.

Algorithms↗
PubMedDate not supplied

Ataxia of stance in different types of alcohol dependence--a posturographic study.

The aim of this study was to assess the prevalence of ataxia of stance in different types of alcohol-dependent patients. Posturographic measurements were performed in 82 abstinent alcohol-dependent patients and 54 healthy controls in order to analyse postural control. According to Lesch and co-workers, alcohol dependence was classified as total abstinence (Type I), drinking without loss of control (Type II), fluctuating course (Type III), and persistent severe drinking (Type IV). The mechanisms of alcohol dependence in these subtypes can be summarized as follows: Type I patients drink alcohol to counteract symptoms of alcohol withdrawal; Type II patients use alcohol as an agent for solving conflicts; Type III patients drink alcohol to 'treat' an affective disorder; and Type IV patients have a history of pre-alcoholic neurological and/or psychiatric disorders. The neurological examination showed pathological findings in 39%, whereas posturographic measurements uncovered impaired postural control in 61% (chi2 = 8.8, P = 0.003). Comparing the different study groups revealed that ataxia of stance was most common in alcohol-dependent patients classified as Type IV (tau = 0.24, P = 0.005). In conclusion, posturographic measurements are superior to the clinical examination in detecting postural imbalance in alcohol-dependent patients. The prevalence of postural imbalance is highest in patients classified by Lesch as Type IV. Consequently, this type of alcohol dependence -- characterized by pre-alcoholic neurological and/or psychiatric disorders, bears the highest risk of developing ataxia of stance.

Adult↗
PubMed2005

Role of the basal ganglia in balance control.

In this review paper, we summarize the important contributions of the basal ganglia to the regulation of postural control. After a brief overview of basal ganglia circuitries, the emphasis is on clinical observations in patients with focal lesions in parts of the basal ganglia, as the impairments seen here can serve to highlight the normal functions of the basal ganglia nuclei in postural control. Two particularly relevant functions are discussed in detail: first, the contribution of the basal ganglia to flexibility and to gaining control of balance-correcting responses, including the ability to lend priority to the elements of a postural task; and second, processing afferent information by the basal ganglia, which is increasingly recognized as being highly relevant for postural control.

Adaptation, Physiological↗
PubMed2004

Not just standing there: the use of postural coordination to aid visual tasks.

Postural control is an integral part of all physical behavior. Recent research has indicated that postural control functions in a manner that facilitates other higher order (suprapostural) tasks. These studies, while showing that postural sway is modulated in a task specific manner, have not examined the form of postural coordination that allows for the achievement of these higher behavioral goals. The current study examined the relation between visual task constraints (viewing distance), environmental constraints (changes in the surface of support), and the postural coordination employed to complete the task. Thirty-one participants were asked to perform a reading task while standing on various surfaces. Postural motion was recorded from the head, cervico-thoracic spine, sacrum (hip), and ankle. It was found that body segment coordination changed as a function of surface characteristics and task constraints. Additionally, the overall pattern of postural sway (head motion) replicated that which was found by Stoffregen et al. [J. Exp. Psychol. Human Percep. Perform. 25 (6) (1999) 1641]. These findings suggest that postural adaptation involves more than basic reduction or increase of motion; it involves the functional coordination of body segments to achieve a particular goal. The data further suggest that there is a need to examine postural control in the absence of external perturbations.

Adaptation, Physiological↗
PubMed2006

Balance in single-limb stance after surgically treated ankle fractures: a 14-month follow-up.

BACKGROUND: The maintenance of postural control is fundamental for different types of physical activity. This can be measured by having subjects stand on one leg on a force plate. Many studies assessing standing balance have previously been carried out in patients with ankle ligament injuries but not in patients with ankle fractures. The aim of this study was to evaluate whether patients operated on because of an ankle fracture had impaired postural control compared to an uninjured age- and gender-matched control group. METHODS: Fifty-four individuals (patients) operated on because of an ankle fracture were examined 14 months postoperatively. Muscle strength, ankle mobility, and single-limb stance on a force-platform were measured. Average speed of centre of pressure movements and number of movements exceeding 10 mm from the mean value of centre of pressure were registered in the frontal and sagittal planes on a force-platform. Fifty-four age- and gender-matched uninjured individuals (controls) were examined in the single-limb stance test only. The paired Student t-test was used for comparisons between patients' injured and uninjured legs and between side-matched legs within the controls. The independent Student t-test was used for comparisons between patients and controls. The Chi-square test, and when applicable, Fisher's exact test were used for comparisons between groups. Multiple logistic regression was performed to identify factors associated with belonging to the group unable to complete the single-limb stance test on the force-platform. RESULTS: Fourteen of the 54 patients (26%) did not manage to complete the single-limb stance test on the force-platform, whereas all controls managed this (p < 0.001). Age over 45 years was the only factor significantly associated with not managing the test. When not adjusted for age, decreased strength in the ankle plantar flexors and dorsiflexors was significantly associated with not managing the test. In the 40 patients who managed to complete the single-limb stance test no differences were found between the results of patients' injured leg and the side-matched leg of the controls regarding average speed and the number of centre of pressure movements. CONCLUSION: One in four patients operated on because of an ankle fracture had impaired postural control compared to an age- and gender-matched control group. Age over 45 years and decreased strength in the ankle plantar flexors and dorsiflexors were found to be associated with decreased balance performance. Further, longitudinal studies are required to evaluate whether muscle and balance training in the rehabilitation phase may improve postural control.

Adult↗
PubMed2002

Gait initiation in community-dwelling adults with Parkinson disease: comparison with older and younger adults without the disease.

BACKGROUND AND PURPOSE: Initiation of gait requires transitions from relatively stationary positions to stability with movement and from double- to single-limb stances. These are deliberately destabilizing activities that may be difficult for people with early Parkinson disease (PD), even when they have no problems with level walking. We studied differences in postural stability during gait initiation between participants with early and middle stages of PD (characterized by Hoehn and Yahr as stages 1-3) and 2 other groups of participants without PD--older and younger adults. SUBJECTS: The mean ages of the 3 groups of participants were as follows: subjects with PD, 69.3 years (SD=5.7, range=59-78); older subjects without PD, 69.0 years (SD=3.9, range=65-79); and younger subjects without PD, 27.5 (SD=3.9, range=22-35). METHODS: A 3-dimensional motion analysis system was used with 2 force platforms to obtain data for center of mass (COM) and center of pressure (COP). The distance between the vertical projections of the COM and the COP (COM-COP distance) was used to reflect postural control during 5 events in gait initiation. RESULTS: By use of multivariate analysis of variance, differences in COM-COP distance were found among the 3 groups. An analysis of variance indicated differences for 4 of the 5 events in gait initiation. A Scheffe post hoc analysis demonstrated differences in gait initiation between the subjects with PD and both groups of subjects without PD (2 events) and between the subjects with PD and the younger subjects without PD (2 events). DISCUSSION AND CONCLUSION: The COM-COP distance relationship was used to measure postural control during the transition from quiet standing to steady-state gait. Differences between groups indicated that individuals with impaired postural control allow less COM-COP distance than do individuals with no known neurologic problems. The method used could prove useful in the development and assessment of interventions to improve ambulation safety and enhance the independence of people with impaired postural control.

Adult↗
PubMed1999

A new rehabilitation training system for postural balance control using virtual reality technology.

A new rehabilitation training system, designated as a virtual cycling system, was developed to improve postural balance control by combining virtual reality (VR) technology with a bicycle. Several parameters including path deviation, path deviation velocity, cycling time, and head movement were extracted and evaluated to quantify the extent of control. The system was effective as a training device and, in addition, the technology might have a wider applicability to the rehabilitation field.

Adult↗
PubMed2001

What can posturography tell us about vestibular function?

Patients with balance disorders want answers to the following basic questions: (1) What is causing my problem? and (2) What can be done about my problem? Information to fully answer these questions must include status of both sensory and motor components of the balance control systems. Computerized dynamic posturography (CDP) provides quantitative assessment of both sensory and motor components of postural control along with how the sensory inputs to the brain interact. This paper reviews the scientific basis and clinical applications of CDP. Specifically, studies describing the integration of vestibular inputs with other sensory systems for postural control are briefly summarized. Clinical applications, including assessment, rehabilitation, and management are presented. Effects of aging on postural control along with prevention and management strategies are discussed.

Posture↗
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↗
PubMed1999

Beneficial effect of proprioceptive physical activities on balance control in elderly human subjects.

Age and lack of physical activities may both be responsible for poor balance control. Conversely, physical activities may modulate postural control in elderly individuals. We examined which type of exercise might prove most beneficial to retain or regain proper balance. Nineteen healthy subjects, aged over 60, regularly practicing proprioceptive (group I) or bioenergetic (group II) physical activities and 21 controls only walking on a regular basis, were studied. All were submitted to a dynamic posturographic test and to a test evaluating lower limbs muscular strength. Control individuals displayed the poorest balance and muscular performance. Group I subjects had the best postural control with average muscular strength. In group II, muscular strength was significantly increased, but balance control was of poor quality. Proprioceptive exercise therefore appears to have the best impact on balance control.

Aged↗