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At least 253 records · Page 14Linked to original sources
PubMed2001

The interacting effects of cognitive demand and recovery of postural stability in balance-impaired elderly persons.

BACKGROUND: Although postural recovery is attentionally demanding in healthy elderly persons, an inability to recover balance due to competition for attentional resources between the postural system and a second task could contribute to falls in older adults with poor balance. This study examined the attentional demands of balance recovery from a mild postural disturbance in balance-impaired elderly persons. A second purpose of this research was to determine the effect of performing a cognitive task on the recovery of balance in balance-impaired elderly persons. METHODS: Fifteen healthy older adults and 13 older adults with clinical balance impairment were exposed to balance disturbances by means of sudden movement of a platform on which they stood. A dual-task paradigm where postural recovery served as the primary task and verbal reaction time to auditory tones served as the secondary task was used to assess attentional demand. To determine the effect of the cognitive task on postural recovery, kinetic, kinematic, and neuromuscular measures of a feet-in-place response were investigated. RESULTS: Balance recovery using a feet-in-place response was attentionally demanding in both groups of older adults and was more demanding in balance-impaired than in healthy elderly persons. With the concurrent performance of a cognitive task, balance-impaired elderly persons took longer to stabilize their center of pressure and regain balance than in a single task, while healthy elderly persons showed no change between conditions. In addition, only balance-impaired elderly individuals had a greater center-of-pressure resultant velocity during recovery in a dual-task compared with a single-task situation. CONCLUSIONS: The ability to recover balance using a feet-in-place response was more attentionally demanding in balance-impaired than in healthy elderly persons. The recovery of balance was also slower and less efficient in balance-impaired elderly persons when simultaneously performing a cognitive task, whereas the ability of healthy elderly individuals to recover was not influenced by concurrent task demands. This suggests that dual-task performance may contribute to postural instability and falls in balance-impaired elderly individuals.

Accidental Falls↗
PubMed2006

Striatal dopamine denervation and sensory integration for balance in middle-aged and older adults.

UNLABELLED: The dopaminergic system of the basal ganglia has been implicated in the integration of sensory information important for balance based on studies in patients with Parkinson's disease. Striatal dopaminergic activity decreases with normal aging. OBJECTIVE: To investigate the relationship between regional striatal dopaminergic denervation and sensory information integration important for balance in middle-aged and older adults. METHODS: Community-dwelling subjects (N=35; age 41-83) with no clinical diagnoses of conditions affecting balance underwent dynamic posturography testing (Sensory Organization Test/SOT) and C-11-beta-CFT dopamine transporter positron emission tomography. RESULTS: Reduced ventral striatal dopamine was significantly correlated with increased anterior-posterior sway in three SOT conditions. Specifically, during quiet standing (SOT Conditions #1, 2) and when repeatedly to sway-referenced visual environments (SOT Condition #3, Trial #3), pre-synaptic dopaminergic denervation in the anteroventral striatum explained over 20-25% of the variability in sway magnitude above and beyond that explained by age (p<or=0.01). Striatal dopaminergic denervation did not impact balance in sway-referenced floor conditions. CONCLUSIONS: The SOT Condition #3 findings suggest that, in normal aging, the central ability to inhibit balance destabilizing vision-related postural control processes depends at least partially on striatal dopaminergic pathways. In contrast, striatal dopaminergic denervation does not appear to impair the ability to disengage destabilizing proprioceptive inputs and to trigger the vestibular control system during challenging sensory perturbations (SOT Conditions #4-6). Finally, quiet standing results (SOT Conditions #1, 2) justify the need to further investigate the impact of striatal dopaminergic denervation on the ability to tune muscle tone in healthy adults.

Accidental Falls↗
PubMed2005

Sensory deprivation and balance control in idiopathic scoliosis adolescent.

Balance control is influenced by the availability and integrity of sensory inputs as well as the ability of the balance control mechanisms to tailor the corrective action to the gravitational torque. In this study, to challenge balance control, visual and ankle proprioceptive information were perturbed (eyes closed and/or tendon vibration). We masked sensory inputs in order: (1) to test the hypothesis that adolescent idiopathic scoliosis (AIS), compared to healthy adolescent, relies more on ankle proprioception and/or visual inputs to regulate balance and (2) to determine whether it is the variation or the amplitude of the balance control commands of AIS that leads to greater body sway oscillations during sensory deprivation. By manipulating the availability of the sensory inputs and measuring the outcomes, center of pressure (CP) range and velocity variability, we could objectively determine the cost of visual and/or ankle proprioception deprivation on balance control. The CP range was larger and the root mean square (RMS) of the CP velocity was more variable for AIS than for control participants when ankle proprioception was perturbed. This was observed regardless of whether vision was available or not. The analysis of the sway density curves revealed that the amplitude rather than the variation of the balance control commands was related to a larger CP range and greater RMS CP velocity for AIS. The present results suggest that AIS, compared to control participants, relies much more on ankle proprioception to control the amplitude of the balance control commands.

Adolescent↗
PubMed1968

Auditory detection and perception in normal man and in patients with adrenal cortical insufficiency: effect of adrenal cortical steroids.

Auditory detection thresholds for sinusoidal tones and various tests of auditory perception were determined in 12 patients with adrenal cortical insufficiency (seven with Addison's disease and five with panhypopituitarism) and compared to those in normal volunteers. In adrenal cortical insufficiency auditory detection sensitivity was significantly more acute than normal, and judgments of loudness and of the contralateral threshold shift were made at levels more than 20 db below those of normal subjects. Thus both the lower and the upper limits of the dynamic auditory range are significantly decreased in these patients. Speech discrimination ability of the patients was significantly impaired as was their difference limens, their alternate binaural loudness balances, and their ability to localize tones in space. Treatment of the patients with deoxycorticosterone acetate decreased serum potassium concentration, raised serum sodium concentration, and produced gains in body weight but did not alter auditory detection or perception. Treatment with prednisolone or with maintenance doses of carbohydrate-active steroids returned auditory detection and perception to normal in every patient tested. The inability of the untreated patients to perform the various auditory perception tasks indicates that they have a defect in their ability to integrate incoming sensory stimuli. This defect may be related to the alteration in the timing of transmission of neural impulses along axons and across synapses which occurs in these patients when their carbohydrate-active steroid is removed. This decreased integrative capacity occurs at the same time that they are able to detect many types of sensory stimuli significantly better than normal subjects. This interrelationship between increased detection sensitivity and decreased perceptual ability is dependent upon the absence of carbohydrate-active steroids, for when these steroids are replaced both detection sensitivity and perceptual ability revert to normal.

Addison Disease↗
PubMed2003

The positive effects of negative work: increased muscle strength and decreased fall risk in a frail elderly population.

BACKGROUND: The objective of this study was to determine if a chronic eccentric training intervention, i.e., negative work, could limit or even reverse sarcopenia and its related impairments and functional limitations. Is high-force eccentric training tolerable by elderly people and will it result in improved muscle size, strength, balance, and fall risk? METHODS: 21 frail elderly subjects (mean age, 80 years) experienced 11 weeks of lower extremity resistance training. The experimental eccentric (ECC) group (n=11) performed negative work while exercising on a high-force eccentric ergometer. The active "controls" performed traditional (TRAD) (n=10) lower extremity resistance exercises (weight training). Muscle fiber cross-sectional area and strength, balance, stair descending abilities, and fall risk were assessed prior to and following this intervention. RESULTS: All ECC subjects who started the negative work intervention completed the study and reported the training to be relatively effortless; they experienced minimal and transient muscle soreness. Both groups experienced a significant increase in muscle fiber cross-sectional area (ECC=60%, TRAD=41%). Only the ECC group experienced significant improvements in strength (60%), balance (7%), and stair descent (21%) abilities. The timed up and go task improved in both groups, but only the ECC group went from a high to a low fall risk. CONCLUSIONS: These data demonstrate that lower extremity resistance exercise can improve muscle structure and function in those with limited exercise tolerance. The greater strength increase following negative work training resulted in improved balance, stair descent, and fall risk only in the ECC group. Because low energy cost is coupled to high force production with eccentric exercise, this intervention may be useful for a number of patients that are otherwise unable to achieve high muscle forces with traditional resistance exercise.

Accidental Falls↗
PubMed2004

Blunted hypothalamic neuropeptide gene expression in response to fasting, but preservation of feeding responses to AgRP in aging male Brown Norway rats.

Aging mammals lose the ability to maintain energy balance, exhibiting decreased appetite (anorexia) and impaired ability to maintain body weight. To determine the contribution of hypothalamic neuropeptides, two experiments were performed in male Brown Norway rats. To assess the hypothalamic neuropeptide response to food deprivation, young (Y; 4 mo old), middle-aged (M; 13 mo), and old (O; 25 mo) rats were either ad libitum fed or fasted for 72 h (n = 10/group) and killed. Hypothalamic levels of agouti-related peptide (AgRP), proopiomelanocortin (POMC), and cocaine-amphetamine-regulated transcript (CART) mRNA were assessed by in situ hybridization. With aging, arcuate AgRP gene expression decreased and CART mRNA increased, but POMC mRNA did not change. Fasting-induced changes in gene expression of all neuropeptides studied were attenuated with aging. To test the food intake response to appetite-stimulating neuropeptides, Y, M, O, and very old (VO; 33 mo) rats (n = 4-8/group) received one intracerebroventricular injection of each of three treatments: 0.1 nmol AgRP, 2.34 nmol NPY, and saline control. AgRP increased food intake of all groups by 10-20%, compared with saline, and this effect persisted up to 7 days after injection. VO animals were more sensitive to the effects of AgRP than younger animals. In contrast, NPY increased food intake more in Y than in older animals and its effects did not last >24 h. We conclude that the mechanisms by which arcuate nucleus neurons influence appetite are differentially affected by age and speculate that the melanocortin system may be a useful target for treatment of the anorexia of aging.

Aging↗
PubMed2001

Height, surface firmness, and visual reference effects on balance control.

OBJECTIVES: To investigate the effects of height, surface firmness, and visual reference on standing balance in construction workers. DESIGN: Controlled laboratory study with balanced repeated measures. PARTICIPANTS: Twenty four construction workers. SETTING: Test subjects performed standing tasks at ground level as well as at 3 m and 9 m high balconies on firm or deformable surfaces with close visual references included or excluded from their visual field. METHODS: Standing balance was determined from center of pressure as measured by a force platform. Dependent variables were root mean square of sway in medial-lateral and anterior-posterior directions, area of sway, and velocity of sway. RESULTS: Heights without close visual references significantly increased all sway parameters. The effect of height in conditions without close visual references increased dramatically on deformable surfaces. CONCLUSIONS: Elevated work environments and deformable work surfaces negatively affect balance and may be associated with increased risk of fall incidents. Appropriate close visual references increase the ability to maintain balance.

Accidental Falls↗
PubMed1998

Neuromuscular responses to disturbance of balance in children with prenatal exposure to alcohol.

Alcohol-exposed children display delayed motor development and impaired fine- and gross-motor skills, including deficits in the maintenance of balance. In a recent study, we assessed the contribution of visual, somatosensory, and vestibular information to the ability to maintain balance. Our findings suggested that alcohol-exposed children were overly reliant on somatosensory information and were unable to compensate by using the visual and/or vestibular systems. To understand the nature of these observed balance deficits, corrective postural reactions were examined by exposing standing subjects to rapid toe-up movements of the support surface. Subjects for this study were alcohol-exposed (ALC) and normal control (NC) children matched for age and sex. Postural reactions were quantified by measuring electromyographic activity of the triceps surae and anterior tibialis muscles. Analyses revealed no differences between the ALC and NC groups on short- and medium-latency electromyographic responses, which are thought to be involuntary mono- and polysynaptic spinal reflexes, respectively. However, when compared with the NC group, the ALC group displayed increased long-latency responses, which are thought to involve a transcortical pathway. Although we are not able to rule out the possibility of additional peripheral (e.g., vestibular) disturbance as a contributing factor to postural instability, our findings suggest that the balance deficits seen in alcohol-exposed children are, at least in part, central in nature.

Adolescent↗
PubMed2000

Development of a novel method for assessing balance: the quantitative posturography system.

Balance is the ability to maintain equilibrium while sitting or standing. There are a number of different methods which are used to assess balance: technical methods such as sway magnetometry, ataxia meter and force platforms, and clinical methods such as the functional reach test, Berg balance test and fall risk index. The most frequently used technical method is the force platform. There are two types of force platform, a static and a dynamic force platform, of which the dynamic force platform has been found to be more sensitive to detect impaired balance. The quantitative posturography system (QPS) described in this paper is a type of dynamic force platform; however, it has a simpler design than the currently available dynamic force platforms and can match the subject's sway exactly for tilting in the anterio-posterior and medio-lateral directions with its novel design. This paper describes the novel design of the QPS and its calibration.

Biomechanical Phenomena↗
PubMed1995

A cross-sectional validation study of the FICSIT common data base static balance measures. Frailty and Injuries: Cooperative Studies of Intervention Techniques.

BACKGROUND: Two simple balance scales comprising three or four familiar tests of static balance were developed, and their validity and reliability are described. The scales were such that the relative difficulties of the basic tests were taken into consideration. METHODS: Using FICSIT data, Fisher's method was used to construct scales combining ability to maintain balance in parallel, semi-tandem, tandem, and one-legged stances. Reliability was inferred from the stability of the measure over 3-4 months. Construct validity was assessed by cross-sectional correlations. RESULTS: Test-retest reliability (over 3-4 months) was good (r = .66). Validity of the FICSIT-3 scale was suggested by its low correlation with age, its moderate to high correlations with physical function measures, and three balance assessment systems. The FICSIT-4 scale discriminated balance over a wide range of health status; the three-test scale had a substantial ceiling effect in community samples. CONCLUSION: A balance scale was developed that appears to have acceptable reliability, validity, and discriminant ability.

Aged↗
PubMed2000

The effect of hitch-hiking on genes linked to a balanced polymorphism in a subdivided population.

The effect of multi-allelic balancing selection on nucleotide diversity at linked neutral sites was investigated by simulations of subdivided populations. The motivation is to understand the behaviour of self-recognition systems such as the MHC and plant self-incompatibility. For neutral sites, two types of subdivision are present: (1) into demes (connected by migration), and (2) into classes defined by different functional alleles at the selected locus (connected by recombination). Previous theoretical studies of each type of subdivision separately have shown that each increases diversity, and decreases the relative frequencies of low-frequency variants, at neutral sites or loci. We show here that the two types of subdivision act non-additively when sampling is at the whole population level, and that subdivision produces some non-intuitive results. For instance, in highly subdivided populations, genetic diversity at neutral sites may decrease with tighter linkage to a selected locus or site. Another conclusion is that, if there is population subdivision, balancing selection leads to decreased expected FST values for neutral sites linked to the selected locus. Finally, we show that the ability to detect balancing selection by its effects on linked variation, using tests such as Tajima's D, is reduced when genes in a subdivided population are sampled from the total population, rather than within demes.

Alleles↗
PubMed2006

Impaired balance in developmental dyslexia? A meta-analysis of the contending evidence.

BACKGROUND: Developmental dyslexia is typically defined by deficits in phonological skills, but it is also associated with anomalous performance on measures of balance. Although balance assessments are included in several screening batteries for dyslexia, the association between impairments in literacy and deficits in postural stability could be due to the high co-occurrence of dyslexia with other developmental disorders in which impairments of motor behaviour are also prevalent. METHODS: We identified 17 published studies that compared balance function between dyslexia and control samples and obtained effect-sizes for each. Contrast and association analyses were used to quantify the influence of hypothesised moderator variables on differences in effects across studies. RESULTS: The mean effect-size of the balance deficit in dyslexia was .64 (95% CI = .44-.78) with heterogeneous findings across the population of studies. Probable co-occurrence of other developmental disorders and variability in intelligence scores in the dyslexia samples were the strongest moderator variables of effect-size. CONCLUSIONS: Balance deficits are associated with dyslexia, but these effects are apparently more strongly related to third variables other than to reading ability. Deficits of balance may indicate increased risk of developmental disorder, but are unlikely to be uniquely associated with dyslexia.

Attention Deficit Disorder with Hyperactivity↗
PubMed2005

Balance in personal care home residents: a comparison of the Berg Balance Scale, the Multi-Directional Reach Test, and the Activities-Specific Balance Confidence Scale.

PURPOSE: This study used the Berg Balance Scale (BBS), the Multi-Directional Reach Test (MDRT), and the Activitiesspecific Balance Confidence Scale (ABC) to quantify balance of elderly residents of a personal care home. The reliability and construct validity of these measures were also examined. METHODS: Twenty one females and 5 males, 74 to 92 years old, participated. Participants completed each balance test once, during 2 testing sessions. Reliability was quantified using intraclass correlation coefficients (ICCs). Construct validity was quantified using Pearson's correlation coefficients (r) and Cronbach's alpha. RESULTS: The mean (+/-sd) scores were: BBS=41.3+/-9.0, MDRT (forward=5.6+/-3.0 in, backward=2.9+/-2.2 in, right=3.3+/-2.5 in, left=3.7+/-3.1 in), and ABC=54.0+/-24.9%. Inter-rater reliability was good for the BBS and MDRT (ICC=0.88-0.98). Test-retest reliability was moderate to good for all 3 balance tests (ICC=0.66-0.83). Pearson's correlations between the BBS and MDRT were moderate to good (r=0.53-0.78), and correlations involving the ABC were fair to moderate (r=0.41-0.59). Cronbach's alpha was strong (0.80) when only the MDRT and BBS were included. CONCLUSIONS: Results indicate residents of personal care homes are at high fall risk. The balance tests showed moderate to good reliability for this population. The BBS and MDRT appear to be valid measures of motor ability to maintain balance, while the self report ABC appears to measure a different component of the balance construct in this population.

Aged↗
PubMed1988

Vestibulo-ocular reflex and gaze functions in a patient with congenital inner ear anomalies.

We report on the vestibulo-ocular reflex (VOR) and gaze functions during horizontal rotations as well as upright locomotions in a fisherman with congenital inner ear anomalies. The finding of a marked gaze disturbance due to low VOR gain during passive rotations resembled that found in early acquired lesions. There was an improvement during active rotations, suggesting an intensified cervico-ocular reflex. Although head oscillations in the horizontal plane were abnormally large during stepping and running, they were compensated for visually even at high frequencies. The absence of complaints of oscillopsia as well as his ability to achieve proper balance seemed to be accomplished by his optokinetic ability, regularly transformed head oscillations and modified perceptive mechanisms at higher cortical levels.

Adult↗
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↗
PubMed2000

Influence of trauma induced by judo practice on postural control.

Although high-level sports develop specific physiological and sensorimotor abilities involved in balance control, they also increase the risk of injuries. The influence on postural control of lower limb trauma induced by judo practice was examined in healthy and previously injured judoists (PIJ). During static and dynamic tests, performed with or without vision, PIJ achieved the best performances in maintaining proper balance, except for those with the most severe antecedents of trauma. The severity of the pathology appeared to be the most important parameter prejudicial to balance control while the location, frequency and diversity of trauma had only a modest impact. This shows that PIJ develop excellent sensory and cognitive adaptation abilities to constraints involving new patterns of compensation and of body scheme.

Adaptation, Physiological↗
PubMed2001

Age and gender differences in peak lower extremity joint torques and ranges of motion used during single-step balance recovery from a forward fall.

Previous studies have found substantial age and gender group differences in the ability of healthy adults to regain balance with a single step after a forward fall. It was hypothesized that differences in lower extremity joint strengths and ranges of motion (ROM) may have contributed to these observed differences. Kinematic and forceplate data were therefore used with a rigid-link biomechanical model simulating stepped leg dynamics to examine the joint torques and ROM used by subjects during successful single-step balance recoveries after release from a forward lean. The peak ROM and torques used by subjects in the study were compared to published estimates or measured values of the available maxima. No significant age or gender group differences were found in the mean ROM used by the subjects for any given initial lean angle. As initial lean angle increased, larger knee ROM and significantly larger hip ROM were used in the successful recoveries. There were substantial gender differences and some age group differences in peak lower extremity joint torques used in successful recoveries. Both young and older females often used nearly maximal joint torques to recover balance. Subjects' maximum joint strengths in plantarflexion and hip flexion were not good predictors of single-step balance recovery ability, particularly among the female subjects.

Accidental Falls↗