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Results for “Postural control”

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At least 1,405 records · Page 78Linked to original sources

PubMed2005

Effect of high-intensity strength-training on functional measures of balance ability in balance-impaired older adults.

OBJECTIVE: The aim of this study was to evaluate the effect of a 10-week, high-intensity strength-training program targeting key lower extremity muscles for the purpose of improving postural control in balance-impaired older adults. METHODS: A quasi-experimental, delayed entry controlled design was used to evaluate balance ability in balance-impaired older adults after participation in 10 weeks of high-intensity strength training focused on the quadriceps, hamstrings, tibialis anterior, and gastrocnemius muscles. Participants were evaluated using validated clinical measures of functional balance ability: the Berg Balance Scale, the Timed Up and Go, and the Activities-Specific Balance Confidence Scale. RESULTS: After strength training, the exercisers were significantly stronger than the control subjects. They improved significantly on the Berg Balance Scale (P = .030) from a mean score of 48.8 +/- 2.4 of 56 before training to 51.2 +/- 4.3 of 56 after training. The Timed Up and Go (P = .045) and the Activities-Specific Balance Confidence Scale (P = .038) also improved significantly in the experimental group. These changes are associated with a decrease in fall risk. CONCLUSIONS: High-intensity strength training can safely and effectively strengthen lower extremity muscles in balance-impaired older adults, resulting in significant improvements in functional balance ability and decreased fall risk.

Aged↗

PubMed1990

System identification of human joint dynamics.

The dynamics of joint mechanics are a fundamental characteristic of the motor system. They determine the displacements evoked by perturbing forces during postural control and the forces that must be generated to perform a voluntary movement. This article reviews experimental studies of these dynamics, with an emphasis on the behavior of single joints in alert humans. Technical aspects of the experimental and analytic methods that have been used are summarized first. Major results obtained with the different methods are then reviewed, compared, and contrasted. The interpretation of these results in terms of the underlying physiological mechanisms is then considered, with an emphasis on the relative contributions of passive properties of tissue, the mechanical behavior of muscle, and stretch reflexes. Finally, important unanswered questions regarding the dynamics of joint mechanics are reviewed.

Biomechanical Phenomena↗

PubMed1999

A low-cost, portable system for the assessment of the postural response of wheelchair users to perturbations.

Maintaining seated postural stability presents a serious challenge to wheelchair users in vehicles, even during normal driving conditions. The purpose of this research was to develop a system for the study of seated postural control in response to perturbations similar to those that might be experienced during vehicle turning and braking. A servo-controlled tilt platform was constructed to provide a low-cost, small, and easily transportable device for generating precise and repeatable perturbations. Tilt platform operation was examined for accuracy and reproducibility of a desired perturbation. Repeatability was high with a mean signal-to-noise ratio (SNR) of 45.4 for a given perturbation measured across 11 subjects. An initial comparison of stability results obtained on the tilt platform and in a vehicle showed a correspondence, although differences were apparent. The tilt platform has been used successfully to assess balance in spinal cord-injured subjects and to test wheelchair securement systems.

Acceleration↗

PubMed2004

Physical activity after retirement enhances vestibulo-ocular reflex in elderly humans.

Vestibular information decreases in sensitivity with ageing, and its role becomes less important in the regulation of postural control. In addition, the practice of physical activity (PA) helps to improve vestibular sensitivity. This study aimed to evaluate PA-related benefit on vestibular function in 36 subjects split into four groups according to the period of practice. Caloric and rotatory vestibular testings showed that the performance of subjects who had begun practising PA recently were close to those of subjects active for a long time, whereas those of subjects who had stopped practising at an early age were close to those of inactive subjects. Although starting to practise PA has immediate beneficial effects on the vestibule, in terms of vestibular stimulation mechanisms these effects soon disappear if this activity is stopped.

Aged↗

PubMed1979

Pathogenetic and preventive aspects of non-progressive ataxic syndromes.

The article reviews the collected knowledge concerning the non-progressive syndromes of ataxic cerebral palsy. Three syndromes are described: (1) simple ataxia (signs of dyssynergia); (2) ataxic diplegia (ataxia with added diplegic spasticity); and (3) dysequilibrium syndrome (defective postural control and equilibrium). The probable aetiological factors in each syndrome are discussed. In simple ataxia prenatal factors dominate; a high proportion of cases have an untraceable aetiology. Genetic factors play a large rôle, and birthweight is usually normal. With ataxic diplegia the aetiology is again most commonly prenatal, but the proportion of cases with an untraceable aetiology is low. Fetal deprivation of supply and perinatal factors, either isolated or in combination, are important. Low birthweight is frequently found. Genetic aetiological factors are the rule in the dysequilibrium syndrome. Possible preventive measures are discussed on the basis of the aetiological pattern. It is concluded that the possibilities of prevention are greatest in ataxic diplegia.

Asphyxia Neonatorum↗

PubMedDate not supplied

[Characterisation of the influence exerted by the visual factor in patients with balance disorders].

INTRODUCTION: Visual information provides data about the position and movement of the head with respect to objects and serves as a source of reference for the proper perception of verticality. It also plays a specific role in postural control by modifying the efficiency of the vestibular and proprioceptive responses. AIMS: Our aim was to determine how visual information interacts with the symptoms of patients with vertigo, dizziness or instability and to find out the degree of disability it produces. PATIENTS AND METHODS: A study was conducted in 200 patients who had visited because of dizziness, vertigo, instability or loss of balance. We analysed the aspects related to the clinical symptoms of the patients. First, we examined the influence visual stimuli have on the symptoms of vestibular disease itself and their repercussions on the situation between crises. Second, the degree of disability was evaluated on the specific DHI (Dizziness Handicap Inventory) questionnaire. RESULTS: As regards the influence exerted by visual stimulation on the main symptoms, 77.5% reported that it had no effect and 21% said that it made them worse. With regard to the influence of visual stimulation during the intercritical period, it was of no relevance in 53.5% of patients, 26.5% were unaffected, it had an exacerbating effect in 4% and in 7.5% it induced it. Different disorders were observed depending on the type of disease suffered by the patient, and disability was greater according to the influence exerted by the visual factor. CONCLUSIONS: Postural adjustments induced by visual stimuli are capable of triggering instability with serious consequences.

Disability Evaluation↗

PubMed1993

How do physiological components of balance affect mobility in elderly men?

The purpose of this study was to assess the relationship between physiological components of balance and mobility in elderly men without significant disease. Our a priori hypothesis was that physical function is influenced more by accumulated modest impairments than by a single deficit. We examined 39 ambulatory men (> 69 years). Subjects were classified functionally as high, intermediate, or low. Assessment included mobility functions (6-minute walk, mobility skills, reach, 10ft walk time) and physiological components of balance: sensory (vibration, proprioception, vision, vestibular), effector (ankle, knee, hip strength, range of motion), and central processing (response time to perturbations). All mobility functions were significantly (p < .05) different between groups. Impairments in components of postural control were rarely different between groups: the major differences were in ankle strength and visual fields. The number of impaired domains differed across the three groups. Nineteen percent of the low group had at least three domains impaired; none of the intermediate or high groups were impaired in three domains. Fifty-six percent of the low, 20% of the intermediate, and 7% of the high were impaired in two or more domains. Variability in specific mobility measures was also predicted by the number of impaired domains. The decline in physical function may be better explained by the accumulation of deficits across multiple domains than by any single specific impairment.

Accidental Falls↗

PubMed2005

Exploring sitting posture and discomfort using nonlinear analysis methods.

-The possibilities for describing sitting postural control using nonlinear methods was investigated during long-term driving. A total of 85 min of motorway driving intervals (n=12) were used for analysis. The results show that contrary to conventional analysis techniques, nonlinear measures were able to identify a threshold behavior describing the change in discomfort. Visual recurrence plots showed a clear change in the underlying dynamics after 1 hr of driving. The result was confirmed by the statistically significant differences in the stability and complexity of the COP time series, as explored using recurrence quantification analysis and spatio-temporal entropy. The findings of the experiment are consistent with the literature, and present a novel way to uncover transitions of discomfort stages in sitting behavioral research.

Adult↗

PubMed1992

Proprioceptive accuracy in idiopathic scoliosis.

Defects in proprioceptive postural control have been linked to the etiology of idiopathic scoliosis. In particular, a rearrangement of the internal representation of the body has been proposed in these cases. In this study, upper-extremity proprioceptive accuracy was compared among the following groups: 1) patients with idiopathic scoliosis (n = 25); 2) subjects with nonprogressive spinal asymmetry detected by screening in school (n = 23); 3) subjects undergoing behavioral training for nocturnal enuresis (n = 17); and 4) normal subjects (n = 134). A significant inaccuracy was found among the right-handed subjects of the scoliosis and spinal asymmetry groups as compared to the normal group. It is postulated that proprioceptive dysfunction, or borderline function, is a causative factor of spinal asymmetry, which is often observed in early adolescence and which in some cases may be progressive.

Adolescent↗

PubMedDate not supplied

The effect of physiotherapy on standing balance in chronic anterior cruciate ligament insufficiency.

Body sway movements in the frontal plane in a single-limbed stance test were used to assess postural control in 26 patients with chronic anterior cruciate ligament insufficiency. The injured and the noninjured legs were tested before the patients were committed to physiotherapy for 3 to 6 months. Follow-up tests were made after 3, 12, and 36 months. Significant disturbance of the balance of both legs was found before training, compared with a reference group of normal subjects. Values of the noninjured leg were normalized after 3 months of training, but the injured leg still showed an increased body sway. Normal balance parameters on the injured side were found at examination after 12 months. Follow-up examination after 36 months proved persistent normalization of the single-limbed balance on both sides.

Adolescent↗

PubMed2004

A simple method to estimate force plate inertial components in a moving surface.

Support surface perturbations are a common paradigm for the study of balance and postural control. Forces and moments acquired from force plates mounted on, or within, the moving surface will contain components resulting from the inertia of the force plate itself. These force plate inertial components must be removed in order to accurately estimate forces resulting from contact with the force plate. This is particularly important when these contact forces are to be used in further calculations, such as an inverse dynamics analysis of joint kinetics. An estimate of the FPIC can be derived using the kinematics of the moving surface and the inertial properties of the force plate. This technique allowed for a reduction of up to 85% of the peak and integrated FPIC acquired from AMTI (OR6-7) force plates during translations of 0.1m, and surface rotations of 10 degrees, using a ramp stimulus of 150 ms duration.

Biomechanical Phenomena↗

PubMed1993

Effects of increased inertial load in dynamic and randomized perturbed posturography.

Muscular weakness is present in many diseases. The present study attempted to model a relative weakness of postural control muscles by loading the subjects with extra weight, and the effects on EquiTest dynamic posturography and randomized perturbed posturography were assessed. Ten healthy subjects aged 15-39 years (mean 26 years) were used. Their weights ranged 53-82 kg. Equilibrium was measured with and without an extra 20% of body weight attached to the upper part of the trunk by means of pieces of lead metal placed in a specially sewn shirt. Dynamic posturography (EquiTest) comprises a sensory organization test in which the support surface and visual surround are either stable or referenced to the patient's sway, his or her eyes open or closed. In a movement coordination part the platform makes active movements. Antero-posterior sway on a stable support surface with absent or distorted visual cues was marred, and the correction pattern was altered on a movable support surface when the vision was absent. Furthermore, the EquiTest apparatus was driven by special software to produce randomized antero-posterior movements during 45 s. In addition to stable conditions, small and large amplitude perturbations were used. The subject's ability to remain in equilibrium was estimated by the sway velocity and a confidence ellipse sway area during 45 s. During weightbearing, sway areas were larger on the stable support surface both with and without vision. Postural sway velocity was lower when vision was absent both using small and large amplitudes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1996

Influence of auditory precuing on automatic postural responses.

An experiment was conducted to determine the influence of auditory precuing on posture control. Specifically, the influence of a warning signal on the onset latencies of the gastrocnemius (G) and tibialis anterior (TA) muscles was determined. An audible 50-ms tone was presented to subjects standing on a moveable platform and preceded a perturbation to standing balance by 500 ms. The perturbations were produced by an anterior or posterior translation (3 cm at 30 cm/s) of the support surface. Unilateral electromyographic activity was recorded from G and TA muscles. In the first series of trials (series A), the muscle onset latencies following perturbations with a nondirectionally specific precue, an invalid precue, and no precue were compared. In the second series of trials (series B), muscle onset latencies following perturbations with a directionally specific precue, invalid precue, and no precue perturbations were compared. In series A, mean muscle onset latencies decreased following nondirectionally specific precues during forward and backward platform perturbations; respectively, TA 6% (91 +/- 9 ms to 86 +/- 9 ms) and G 7% (93 +/- 6 ms to 87 +/- 5 ms). During series B, the TA and G muscle onset latencies decreased following directionally specific precues by 10.4% (92 +/- 12 ms to 82 +/- 6 ms) and 9.8% (92 +/- 9 ms to 83 +/- 6 ms), respectively. There were no significant differences between the types of precues. Thus, prior knowledge of a forthcoming balance perturbation reduces postural muscle onset latency times. In addition, specific prior knowledge reduces muscle onset latency time in the same manner as does nonspecific prior knowledge.

Acoustic Stimulation↗

PubMed2005

Intrinsic risk factors for inversion ankle sprains in male subjects: a prospective study.

BACKGROUND: Many variables have been retrospectively associated with ankle sprains. However, very little is known about factors predisposing people to these injuries. HYPOTHESIS: Measurable intrinsic factors might predispose male athletes to ankle sprains. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 241 male physical education students were evaluated for possible intrinsic risk factors for inversion sprains at the beginning of their academic study. The evaluated intrinsic risk factors included anthropometrical characteristics, functional motor performances, ankle joint position sense, isokinetic ankle muscle strength, lower leg alignment characteristics, postural control, and muscle reaction time during a sudden inversion perturbation. Subjects were followed prospectively for 1 to 3 years. RESULTS: A total of 44 (18%) of the 241 male subjects sustained an inversion sprain; 4 sprained both ankles. Cox regression analysis revealed that male subjects with slower running speed, less cardiorespiratory endurance, less balance, decreased dorsiflexion muscle strength, decreased dorsiflexion range of motion, less coordination, and faster reaction of the tibialis anterior and gastrocnemius muscles are at greater risk of ankle sprains. CONCLUSION: Based on our findings, it is suggested that running speed, cardiorespiratory endurance, balance, dorsiflexion strength, coordination, muscle reaction, and dorsiflexion range of motion at the ankle are associated with the risk of ankle inversion sprains in male subjects.

Adolescent↗

PubMed1987

Balance and age in the sighted and blind.

This study evaluated the usefulness of a balance test with eyes open and closed to index postural control capability. Experiment 1 was a one-year longitudinal study of 225 subjects aged 50 to 82 years. Comparing the two conditions, balance with eyes open had higher reliability, had greater sensitivity to aging effects, correlated stronger with functional age indices (vital capacity and forced expiratory volume), and showed greater sensitivity to the effects of physical fitness training. Experiment 2 included 22 visually impaired subjects aged 19 to 84 years. Minimally sighted subjects balanced for longer than fully blind subjects, but no differences in balance were found between subjects blind from birth versus those with acquired vision loss. The findings demonstrate the importance of vision to balance and indicate that balance with eyes open is a valid and sensitive test for clinical and research purposes.

Aged↗

PubMed1989

The prevalence of dysequilibrium and related disorders in older persons.

Dysequilibrium disorders such as dizziness, balance and gait changes, and falls are among the most common yet poorly understood medical problems for older persons. A recent analysis of data about people aged 65 and older indicates that dysequilibrium is one of most common diagnoses in short-stay hospitalizations, and it accounts for an average of 4.3 days of medical care. Older people without overt disease of any type tend to perform more poorly on balance tests than do younger people. Gait deficits in many older people are associated with considerable functional impairments. Deficits in postural control are associated with an increased risk of falling. Geriatric dysequilibrium disorders can be caused by one or more factors--vestibular, vascular, visual, neuromuscular, pharmacologic--each of which must be considered to understand and appropriately treat the dysequilibrium. The accurate identification of the cause of dysequilibrium must involve the testing of multiple, interacting systems. The literature suggests that often no clear cause for an older person's dysequilibrium can be found, and indicates the possible existence of presently unappreciated etiologic factors. Progress in understanding these problems probably has been stymied by the fact that only a small, select subgroup of older patients is referred to specialists in otolaryngology. Quite probably, considerable progress on the understanding of the cause, diagnosis, and treatment of geriatric dysequilibria would result from more extensive research collaboration between otorhinolaryngologists, geriatricians, epidemiologists, and other specialists.

Accidental Falls↗

PubMed1992

Rehabilitation and Parkinson's disease.

In this study we evaluated the efficacy of physical therapy together with drug therapy in a group of parkinsonian patients, compared with a group of patients treated using drug therapy only. The physical therapy program lasted four months and included passive and active mobilization exercises, adopted for postural control and equilibrium, walking and prevention of contractures and ankylosis. The assessment was accomplished by means of clinical rating scales and motor performance tests. Patients treated by means of physiotherapy showed an improvement at the end of the study in both clinical scales and motor performance tests. This improvement was noted in both patients with less severe and more severe symptoms as well as in those with shorter and longer disease duration. It is not easy to assess the role played by physical therapy due to the difficulty of an objective evaluation; our results, however, show an improvement in the functional performance of patients and suggest the usefulness of physical therapy associated with drug therapy in a comprehensive treatment for Parkinson's disease.

Aged↗

PubMedDate not supplied

Feasibility of functional electrical stimulation for control of seated posture after spinal cord injury: A simulation study.

We performed this study to determine the feasibility of controlling and stabilizing seated posture with functional electrical stimulation (FES) after paralysis from spinal cord injury (SCI) using computer simulations and a 3-dimensional model of the hip and trunk. We used the model to approximate the range of postures in the sagittal and transverse planes attainable by a seated subject and to estimate the maximum restorative moment that could be produced in a neutral posture in response to a disturbance. The simulations predicted that approximately 28 degrees of forward flexion in the sagittal plane (combined hip and trunk) and 9 degrees of lateral bending in the transverse plane should be possible with FES and that a maximum disturbance rejection moment of approximately 45 newton meters could be expected with the chosen muscle set. We tested a subject with a motor complete thoracic SCI and implanted electrodes in a subset of the selected muscles to compare the moments the subject required to maintain various hip and trunk positions with those predicted by the model. Although a significant range of seated postures was possible with FES, the data demonstrated that more complete activation of the paralyzed muscles would be needed for the subject to fully achieve the theoretical range of motion. With further refinements, we could apply these techniques to the design of control systems for regulation of seated posture and dynamic motion of the torso.

Computer Simulation↗