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1.
Otolaryngol Head Neck Surg ; 117(4): 293-302, 1997 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-9339786

RESUMO

During the last 10 years, computerized dynamic posturography has yielded various patterns of sway on the sensory organization test and the motor control test that have been associated with a variety of organic balance disorders. Some aspects of performance during computerized dynamic posturography, however, are under conscious control. Voluntary movements not indicative of physiologic response to balance system stimulation can also affect computerized dynamic posturography results. Quantification of nonorganic or "aphysiologic" response patterns in normal subjects, patients, and suspected malingerers is crucial to justify use of computerized dynamic posturography for identification of physiologically inconsistent results. For this purpose the computerized dynamic posturography records of 122 normal subjects, 347 patients with known or suspected balance disorders, and 72 subjects instructed to feign a balance disturbance were critically evaluated by use of seven measurement criteria, which were postulated as indicating aphysiologic sway. Each criterion was scored with a standard calculation of the raw data in a random, blinded fashion. The results of this multicenter study show that three of the seven criteria are significantly different in the suspected "malingerer" group when compared with either the normal or patient group. The relative strength of each criterion in discerning organic from nonorganic sway provides the examiner with a measure of reliability during platform posture testing. This study demonstrates that computerized dynamic posturography can accurately identify and document nonorganic sway patterns during routine assessment of posture control.


Assuntos
Equilíbrio Postural/fisiologia , Postura/fisiologia , Desempenho Psicomotor , Transtornos de Sensação/fisiopatologia , Testes de Função Vestibular , Adulto , Idoso , Diagnóstico por Computador , Técnicas de Diagnóstico Neurológico , Humanos , Pessoa de Meia-Idade , Valores de Referência , Reprodutibilidade dos Testes , Transtornos de Sensação/diagnóstico , Sensibilidade e Especificidade
2.
Med Sci Sports Exerc ; 29(7 Suppl): S213-21, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9247918

RESUMO

OBJECTIVES: Athletic trainers and team physicians are often faced with decisions concerning the severity and timing of an athletes return to play following mild head injury (MHI). These decisions can be the most difficult ones facing clinicians because of the limited amount of quantitative information indicating injury severity. Several authors have published guidelines for return to play following MHI, however these guidelines are based on limited scientific data. The purpose of this paper was to examine the effects of MHI on two objective measures, postural stability and cognitive function, to determine their usefulness in MHI assessment. The data gathered from these two measures has the potential to establish recovery curves based on objective data. METHODS: Eleven Division I collegiate athletes who sustained a MHI and eleven matched control subjects were assessed for postural stability and cognitive function at four intervals following injury. Postural stability was assessed using the Sensory Organization Test on the NeuroCom Smart Balance Master. Cognitive functioning was measured through the use of four neuropsychological tests: Stroop Test, Trail Making Test, Digits Span and Hopkins Verbal Learning Test. Separate mixed model repeated measures ANOVAs were calculated for the composite score and three ratio (vestibular, visual and somato-sensory) scores from the Sensory Organization Test and the scores from the neuropsychological test to reveal significant differences between groups and across days postinjury. RESULTS: A significant group by day interaction for overall postural stability (composite score) revealed that MHI athletes displayed increased postural instability for the first few days following MHI (p < .05). Analysis of the ratio scores revealed a significant interaction for the visual ratio. No significant group differences were revealed for any of the neuropsychological tests (p > .05), however significant day differences were revealed (p < .05). CONCLUSIONS: The results from this study indicate that athletes demonstrate decreased stability until 3 days postinjury. It appears this deficit is related to a sensory interaction problem, whereby the injured athlete fails to use their visual system effectively. These findings suggest that measures of postural stability may provide clinicians with a useful clinical tool for determining when an athlete may safely return to competition, although these findings need to be confirmed in larger groups of athletes.


Assuntos
Traumatismos em Atletas/classificação , Cognição , Traumatismos Cranianos Fechados/classificação , Equilíbrio Postural , Postura , Adolescente , Adulto , Traumatismos em Atletas/diagnóstico , Feminino , Guias como Assunto , Traumatismos Cranianos Fechados/diagnóstico , Humanos , Masculino , Segurança/normas , Esportes/normas , Fatores de Tempo
3.
J Theor Biol ; 180(3): 257-70, 1996 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-8759531

RESUMO

Healthy human subjects can maintain adequate balance despite distorted somatosensory or visual feedback or vestibular feedback distorted by a peripheral vestibular disorder. Although it is not precisely known how this sensorimotor integration task is achieved, the nervous system coordinates information from multiple sensory systems to produce motor commands differently in different sensory environments. These different ways of coordinating sensory information and motor commands can be thought of as "sensorimotor states". The way the nervous system distributes the monitoring of postural sway among states is analysed in this paper as a logical structure of transitions between states. The form of the transition structure is specified and distinguished from a finite state machine. The hypothesis that the nervous system could use a transition structure to maintain balance is tested by developing transition structures which are consistent with a set of experimental observations of postural control in healthy subjects and three groups of patients with peripheral vestibular disease.


Assuntos
Modelos Neurológicos , Equilíbrio Postural/fisiologia , Desempenho Psicomotor/fisiologia , Transtornos de Sensação/fisiopatologia , Humanos
4.
Am J Otol ; 17(3): 401-9, 1996 May.
Artigo em Inglês | MEDLINE | ID: mdl-8817017

RESUMO

Living with an uncompensated, abnormal vestibular system requires oppressive modification of life style and often prevents return to work and activities of daily living. Patients with vestibular abnormalities were studied to determine the minimal residual vestibular function required to achieve compensation. Three groups of patients with (a) complete unilateral loss of vestibular function with normal horizontal canal-vestibulo-ocular (HCVOR) function in the opposite ear, (b) complete unilateral loss with abnormal HCVOR function in the opposite ear, and (c) bilateral reduction of vestibular function from aminoglycoside toxicity underwent vestibuloocular (VOR), optokinetic (OKN), visual-VOR (VVOR), and computerized dynamic posturography (CDP) tests before and after therapeutic procedures. Results suggest that a minimal VOR response amplitude must be present for compensation of VVOR function to occur. The roles of VOR and OKN phase shifts in vestibular compensation are more complicated and require further study. Compensation of vestibulospinal function does not necessarily accompany VOR or VVOR compensation. Ascending and descending vestibular compensatory mechanisms may involve different spatial sensory inputs. Results of these studies have important implications for the diagnosis and treatment of patients with vestibular disorders, including selection and monitoring of patients for therapeutic regimens such as vestibular nerve section and streptomycin therapy.


Assuntos
Doenças Vestibulares/diagnóstico , Doenças Vestibulares/fisiopatologia , Vestíbulo do Labirinto/fisiopatologia , Humanos , Qualidade de Vida , Estreptomicina/uso terapêutico , Doenças Vestibulares/tratamento farmacológico , Testes de Função Vestibular
5.
J Neurol Sci ; 111(1): 46-58, 1992 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-1402997

RESUMO

In order to identify the types of postural deficits seen in parkinsonian patients with postural instability, we compared the performance of parkinsonian subjects with young and old control subjects in 3 aspects of postural control: (1) the use of sensory information for postural orientation, (2) the coordination of postural movement patterns in response to surface displacements, and (3) the flexible modification of postural response patterns to changes in support conditions. Parkinsonian subjects had very small sway, even under altered sensory conditions. Postural response latencies to displacements were also normal. Postural instability was associated with abnormal patterns of postural responses including excessive antagonist activity and inflexibility in adapting to changing support conditions. Some parkinsonian subjects appeared to have difficulty sequencing motor programs for postural correction. The parkinsonian subjects appeared stiffer since the rate-of-change of sway in response to displacements was reduced. Levodopa improved postural coordination but not the flexible adaptation to changing support conditions.


Assuntos
Doença de Parkinson/fisiopatologia , Postura/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/fisiologia , Eletromiografia , Feminino , Humanos , Levodopa/uso terapêutico , Masculino , Pessoa de Meia-Idade , Músculos/fisiopatologia , Doença de Parkinson/tratamento farmacológico , Equilíbrio Postural/efeitos dos fármacos , Reflexo/fisiologia
6.
Neurol Clin ; 8(2): 331-49, 1990 May.
Artigo em Inglês | MEDLINE | ID: mdl-2193215

RESUMO

This article reviews the basic concepts underlying the balance system, describes the information provided by dynamic posturography, and explains how the technique complements and expands on the information provided by traditional tests of vestibular function.


Assuntos
Tontura/diagnóstico , Equilíbrio Postural/fisiologia , Postura , Testes de Função Vestibular , Tontura/fisiopatologia , Humanos
7.
Exp Brain Res ; 82(1): 167-77, 1990.
Artigo em Inglês | MEDLINE | ID: mdl-2257901

RESUMO

This study examines the roles of somatosensory and vestibular information in the coordination of postural responses. The role of somatosensory information was examined by comparing postural responses of healthy control subjects prior to and following somatosensory loss due to hypoxic anesthesia of the feet and ankles. The role of vestibular information was evaluated by comparing the postural responses of control subjects and patients with bilateral vestibular loss. Postural responses were quantified by measuring 1) spatial and temporal characteristics of leg and trunk EMG activation; 2) ankle, knee, and hip joint kinematics, and 3) surface forces in response to anterior and posterior surface translations under different visual and surface conditions. Results showed that neither vestibular nor somatosensory loss resulted in delayed or disorganized postural responses. However, both types of sensory deficits altered the type of postural response selected under a given set of conditions. Somatosensory loss resulted in an increased hip strategy for postural correction, similar to the movement strategy used by control subjects while standing across a shortened surface. Vestibular loss resulted in a normal ankle strategy but lack of a hip strategy, even when required for the task of maintaining equilibrium on a shortened surface. Neither somatosensory nor vestibular loss resulted in difficulty in utilizing remaining sensory information for orientation during quiet stance. These results support the hypothesis that cutaneous and joint somatosensory information from the feet and ankles may play an important role in assuring that the form of postural movements are appropriate for the current biomechanical constraints of the surface and/or foot. The results also suggest that vestibular information is necessary in controlling equilibrium in a task requiring use of the hip strategy. Thus, both somatosensory and vestibular sensory information play important roles in the selection of postural movement strategies appropriate for their environmental contexts.


Assuntos
Postura/fisiologia , Reflexo Vestíbulo-Ocular/fisiologia , Doenças Vestibulares/fisiopatologia , Vestíbulo do Labirinto/fisiologia , Adulto , Tornozelo/fisiologia , Eletromiografia , Quadril/fisiologia , Humanos , Hipóxia/psicologia , Pessoa de Meia-Idade , Movimento/fisiologia , Músculos/fisiologia , Vestíbulo do Labirinto/lesões
8.
Ann Otol Rhinol Laryngol ; 98(11): 884-9, 1989 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-2817680

RESUMO

Long-term recovery from surgically induced unilateral loss of vestibular function was studied in 14 patients. Seven patients underwent surgical extirpation or section of the vestibular nerve, and seven patients underwent labyrinthectomy without vestibular nerve section. The vestibulo-ocular reflex (VOR) and postural control were evaluated preoperatively and monitored for up to 4 years postoperatively with use of pseudorandom rotation (combined sinusoidal frequencies from 0.009 to 1.5 Hz) and moving platform posturography. Immediately following surgery all patients showed minimal reductions in the VOR gain constant, but marked reduction in the time constant, and marked increase in slow eye velocity bias. Bias returned to normal values within about 10 days, but time constants never returned to normal values. Results of standard Romberg tests in these patients were normal throughout the preoperative and postoperative periods. However, all patients showed marked postural control abnormalities in tests of the ability to maintain balance in unusual sensory environments in the immediate postoperative period. Seventy-five percent of the patients eventually recovered normal postural control. Postural control returned to near baseline performance with a time course similar to that of the VOR bias. However, postural control also continued to improve after the recovery of VOR bias was complete.


Assuntos
Postura , Reflexo Vestíbulo-Ocular/fisiologia , Nervo Vestibular/cirurgia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Eletroculografia , Feminino , Humanos , Masculino , Doença de Meniere/fisiopatologia , Doença de Meniere/cirurgia , Pessoa de Meia-Idade , Neuroma Acústico/fisiopatologia , Neuroma Acústico/cirurgia , Equilíbrio Postural , Rotação , Testes de Função Vestibular , Nervo Vestibular/fisiopatologia
9.
J Neurophysiol ; 62(4): 841-53, 1989 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-2809706

RESUMO

1. The effect of central set on automatic postural responses was studied in humans exposed to horizontal support-surface perturbations causing forward sway. Central set was varied by providing subjects with prior experience of postural stimulus velocities or amplitudes under 1) serial and random conditions, 2) expected and unexpected conditions, and 3) practiced and unpracticed conditions. In particular, the influence of central-set conditions was examined on the pattern and magnitude of six leg and trunk electromyograph (EMG) activations and associated ankle torque responses to postural perturbations with identical stimulus parameters. 2. The scaling of initial agonist integrated EMG (IEMG) and torque responses to postural perturbation amplitude disappeared when perturbation amplitudes were randomized. This finding suggests that the initial magnitude of postural responses were centrally set to anticipated postural perturbation amplitudes based on sequential experience with the stimulus. 3. Expectation of postural stimulus amplitude had a significant effect on initial torque responses; subjects overresponded when a larger perturbation was expected and underresponded when a smaller perturbation was expected. Expectation of postural stimulus velocity had a smaller effect on initial torque responses, and subjects consistently overresponded when the velocity of the perturbation was unexpected. This difference in amplitude and velocity expectation may be because of the capacity to encode stimulus velocity, but not amplitude information, into the earliest postural responses of the current trial. The relative strength of amplitude and velocity central-set effects varied widely with individual subjects. 4. Central-set conditions did not affect initial EMG response latencies (100 +/- 20 ms, mean +/- SD) or the relative onset of proximal and distal agonists and antagonists. Unexpected or unpracticed stimulus amplitudes, however, were associated with significant late activation of ankle antagonist, tibialis. Thus errors in initial response magnitude because of central-set effects appear to be partially corrected by reciprocal antagonist activity. Agonist IEMG, however, did not always reflect significant changes in torque responses with central-set conditions. 5. Expectation of postural stimulus amplitude and velocity had two different types of effects on the magnitudes of postural responses: 1) a directionally specific, central-set effect consisting of either increased or decreased responses, depending on expectation of stimulus amplitude; and 2) a nonspecific enhanced response to novel stimulus velocities with a gradual reduction when a velocity was presented repeatedly. Two different neural mechanisms are proposed for these two adaptive effects. 6. Reduction of postural response magnitude and antagonist activity during practice may be partially explained by adaptive mechanisms based on expectation because of prior experience with stimulus velocity and amp


Assuntos
Sistema Nervoso Central/fisiologia , Postura/fisiologia , Adulto , Tornozelo , Fenômenos Biomecânicos , Eletromiografia , Retroalimentação , Humanos , Músculos/inervação , Músculos/fisiologia , Estimulação Física
10.
Prog Brain Res ; 80: 411-8; discussion 395-7, 1989.
Artigo em Inglês | MEDLINE | ID: mdl-2699375

RESUMO

We analyse two components of posture control in standing human subjects: (1) the mechanical properties which constrain the body's ability to execute stabilizing postural movements and (2) the mechanical and neural properties which constrain the ability of the vestibular system to sense changes in body orientation. Rules are then proposed to describe the central organization of posture controls within the sensory and mechanical constraints. The organizational rules and knowledge of constraints are combined to predict the effects of selective semicircular canal and utricular otolith lesions on postural stability and the patterns of body and head movements used to maintain balance. Our analysis leads to the prediction that semicircular canal and otolith deficits destabilize patients at different frequencies, and force them to use different patterns of body and head movements. These predictions are compared to posture controls observed in patients with different types of vestibular deficits. The additional steps required to prove or disprove the theory are discussed.


Assuntos
Músculos/inervação , Neurônios Aferentes/fisiologia , Postura , Doenças Vestibulares/fisiopatologia , Núcleos Vestibulares/fisiologia , Humanos , Músculos/fisiologia , Núcleos Vestibulares/fisiopatologia
11.
J Neurophysiol ; 59(6): 1888-905, 1988 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-3404210

RESUMO

1. The role of sensory information in shaping muscle activation patterns to postural perturbations in humans was investigated by varying velocity, amplitude, or duration of the perturbing stimulus. Ten normal subjects were exposed to 120 backward translations of the support surface under conditions of varying velocities (10-35 cm/s, constant amplitude), varying amplitudes (1.2-12 cm, constant velocity), or varying durations (40-800 ms). The effects of perturbation parameters on movement kinematics and EMG latencies, patterns, and integrated areas in six trunk and leg muscles were examined. Integrated EMG activity was normalized across subjects and the early (first 75 ms), middle (second 75 ms), and late (last 350 ms) components were analyzed separately. 2. Ankle, knee, and hip angle trajectories and surface reactive forces suggest that a relatively consistent movement strategy was scaled to the perturbation velocities and amplitudes applied. 3. Short-duration perturbations (75 ms) evoked a single burst of muscle activity (75-100 ms duration) in gastrocnemius, hamstrings, paraspinal, and rectus abdominis muscles at latencies too long to be explained by simple stretch reflexes. EMG latencies, patterns, and integrated areas were independent of the velocity and amplitude of the short-duration perturbations, suggesting a minimal time to incorporate peripheral velocity information into the triggered response. 4. For translations lasting longer than 75 ms, the integrated areas of the early agonist EMG bursts were positively correlated with stimulus velocity. The integrated area of later, more tonic EMG components were best correlated with stimulus amplitude. These relationships were found in both distal (stretched) muscles and in proximal muscles. Absolute latencies (94-145 ms), intersegmental latencies (18-29 ms), and burst durations (75-100 ms) were not influenced by the velocity or amplitude of the stimulus. 5. These results suggest that the spatial and temporal organization of automatic postural responses may be organized independently of response intensity. Within a particular spatial-temporal pattern, the amount of muscle activation appears to be adjusted by sensory information, which specifies velocity and amplitude of the perturbation.


Assuntos
Movimento (Física) , Postura , Adulto , Eletromiografia , Feminino , Humanos , Masculino , Movimento , Músculos/fisiologia , Fatores de Tempo
14.
Exp Brain Res ; 73(3): 648-58, 1988.
Artigo em Inglês | MEDLINE | ID: mdl-3224674

RESUMO

The effect of the direction of unexpected horizontal perturbations of stance on the organization of automatic postural responses was studied in human subjects. We recorded EMG activity from eight proximal and distal muscles acting on joints of the legs and hip known to be involved in postural corrections, while subjects stood on an hydraulic platform. Postural responses to horizontal motion of the platform in 16 different directions were recorded. The amplitude of the EMG responses of each muscle studied varied continuously as perturbation direction was changed. The directions for which an individual muscle showed measurable EMG activity were termed the muscle's "angular range of activation". There were several differences in the response characteristics of the proximo-axial muscles as opposed to the distal ones. Angular ranges of activity of the distal muscles were unipolar and encompassed a range of less than 180 degrees. These muscles responded with relatively constant onset latencies when they were active. Proximo-axial muscles, acting on the upper leg and hip showed larger angular ranges of activation with bimodal amplitude distributions and/or onset latency shifts as perturbation direction changed. While there were indications of constant temporal relationships between muscles involved in responses to perturbations around the sagittal plane, the onset latency relationships for other directions and the response amplitude relationships for all directions varied continuously as perturbation direction was changed. Responses were discrete in that for any particular perturbation direction there appeared to be a single unique response. Thus, while the present results do not refute the hypothesis that automatic postural responses may be composed of mixtures of a few elemental synergies, they suggest that composition of postural responses is a complex process that includes perturbation direction as a continuous variable.


Assuntos
Quadril/fisiologia , Perna (Membro)/fisiologia , Músculos/fisiologia , Postura , Adulto , Humanos , Tempo de Reação/fisiologia
15.
Otolaryngol Head Neck Surg ; 96(2): 125-34, 1987 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-3120085

RESUMO

Clinically, the definitive diagnosis of perilymph fistulas can only be made by tympanotomy. Results of various fistula tests based upon the vestibulo-ocular reflex have not correlated well with findings during tympanotomy. A new fistula test has been developed based upon vestibulo-spinal responses. By systematic removal of both visual and support-surface orientation references from the subject--leaving only vestibular control of postural reflexes--patients with perilymph fistulas demonstrated an increased (sometimes phase-locked) postural sway in response to sinusoidal changes in external auditory canal pressures. Results from 100 consecutively operated ears (64 patients)--77 of whom underwent preoperative and postoperative moving-platform fistula tests--indicate that the test sensitivity is 97 percent for this highly selective patient population. Absolute specificity could not be determined because, on patients without clinical indications for surgery, tympanotomy is contraindicated.


Assuntos
Fístula/diagnóstico , Doenças do Labirinto/diagnóstico , Líquidos Labirínticos , Perilinfa , Testes de Função Vestibular , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Feminino , Fístula/cirurgia , Humanos , Lactente , Recém-Nascido , Doenças do Labirinto/cirurgia , Masculino , Pessoa de Meia-Idade , Postura , Reflexo Vestíbulo-Ocular , Sensibilidade e Especificidade
16.
J Neurophysiol ; 55(6): 1369-81, 1986 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-3734861

RESUMO

We studied the extent to which automatic postural actions in standing human subjects are organized by a limited repertoire of central motor programs. Subjects stood on support surfaces of various lengths, which forced them to adopt different postural movement strategies to compensate for the same external perturbations. We assessed whether a continuum or a limited set of muscle activation patterns was used to produce different movement patterns and the extent to which movement patterns were influenced by prior experience. Exposing subjects standing on a normal support surface to brief forward and backward horizontal surface perturbations elicited relatively stereotyped patterns of leg and trunk muscle activation with 73- to 110-ms latencies. Activity began in the ankle joint muscles and then radiated in sequence to thigh and then trunk muscles on the same dorsal or ventral aspect of the body. This activation pattern exerted compensatory torques about the ankle joints, which restored equilibrium by moving the body center of mass forward or backward. This pattern has been termed the ankle strategy because it restores equilibrium by moving the body primarily around the ankle joints. To successfully maintain balance while standing on a support surface short in relation to foot length, subjects activated leg and trunk muscles at similar latencies but organized the activity differently. The trunk and thigh muscles antagonistic to those used in the ankle strategy were activated in the opposite proximal-to-distal sequence, whereas the ankle muscles were generally unresponsive. This activation pattern produced a compensatory horizontal shear force against the support surface but little, if any, ankle torque. This pattern has been termed the hip strategy, because the resulting motion is focused primarily about the hip joints. Exposing subjects to horizontal surface perturbations while standing on support surfaces intermediate in length between the shortest and longest elicited more complex postural movements and associated muscle activation patterns that resembled ankle and hip strategies combined in different temporal relations. These complex postural movements were executed with combinations of torque and horizontal shear forces and motions of ankle and hip joints. During the first 5-20 practice trials immediately following changes from one support surface length to another, response latencies were unchanged. The activation patterns, however, were complex and resembled the patterns observed during well-practiced stance on surfaces of intermediate lengths.(ABSTRACT TRUNCATED AT 400 WORDS)


Assuntos
Adaptação Fisiológica , Sistema Nervoso Central/fisiologia , Movimento , Músculos/fisiologia , Postura , Adulto , Tornozelo , Fenômenos Biomecânicos , Eletromiografia , Feminino , Quadril , Humanos , Masculino
17.
J Neurophysiol ; 55(6): 1382-94, 1986 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-3734862

RESUMO

This study examines the interactions between anteroposterior postural responses and the control of walking in human subjects. In the experimental paradigm, subjects walked upon a treadmill, gripping a rigid handle with one hand. Postural responses at different phases of stepping were elicited by rapid arm pulls or pushes against the handle. During arm movements, EMG's recorded the activity of representative arm, ankle, and thigh segment muscles. Strain gauges in the handle measured the force of the arm movement. A Selspot II system measured kinematics of the stepping movements. The duration of support and swing phases were marked by heel and toe switches in the soles of the subjects' shoes. In the first experiment, subjects were instructed to pull on the handle at their own pace. In these trials all subjects preferred to initiate pulls near heel strikes. Next, when instructed to pull as rapidly as possible in response to tone stimuli, reaction times were similar for all phases of the step cycle. Leg muscle responses associated with arm pulls and pushes, referred to as "postural activations," were directionally specific and preceded arm muscle activity. The temporal order and spatial distribution of postural activations in the muscles of the support leg were similar when arm pull movements occurred while the subject was standing in place and after heel strike while walking. Activations began in the ankle and radiated proximally to the thigh and then the arm. Activations of swing leg muscles were also directionally specific and involved flexion and forward or backward thrust of the limb. When arm movements were initiated during transitions from support by one leg to the other, patterns of postural activations were altered. Alterations usually occurred 10-20 ms before hell strikes and involved changes in the timing and sometimes the spatial structure of postural activations. Postural activation patterns are similar during in-place standing and during the support phase of locomotion. Walking and posture control appear to be separately organized but interrelated activities. Our results also suggest that the stepping generators, not peripheral feedback time locked to heel strikes, modulate postural activation patterns.


Assuntos
Locomoção , Músculos/fisiologia , Postura , Adulto , Braço , Fenômenos Biomecânicos , Sistema Nervoso Central/fisiologia , Eletromiografia , Humanos , Masculino , Movimento , Tempo de Reação/fisiologia , Reflexo/fisiologia
18.
Int J Aging Hum Dev ; 23(2): 97-114, 1986.
Artigo em Inglês | MEDLINE | ID: mdl-3557634

RESUMO

The following study examined two aspects of balance control in the older adult: the coordination of the timing and the amplitude of muscle responses to postural perturbations, and the ability of the participant to reorganize sensory inputs and subsequently modify postural responses as a consequence of changing environmental conditions. Coordination of muscle activity in postural responses of twelve elderly (sixty-one to seventy-eight years) participants were compared to those of young (nineteen to thirty-eight years) adults using a movable platform and recording the electromyographic activity of muscles of the legs. The following changes were noted in the timing and amplitude of muscle activity within a postural response synergy: increases in the absolute latency of distal muscle responses were observed in all older adults; in five of the twelve older adults temporal reversals of proximal and distal muscle response onset were observed; and there was a breakdown in the correlation of the amplitude of responses within a synergy. The ability of the older adult to balance under conditions of reduced or conflicting sensory information was also impaired. When confronted with functionally inappropriate visual and/or somatosensory inputs, half of the older group lost balance. In most instances, however, the older participants were able to maintain stability during subsequent responses to conflicting stimuli.


Assuntos
Envelhecimento , Músculos/fisiologia , Postura , Sensação/fisiologia , Adaptação Fisiológica , Adulto , Idoso , Idoso de 80 Anos ou mais , Humanos , Pessoa de Meia-Idade , Fisiologia/instrumentação , Tempo de Reação
19.
Ann Otol Rhinol Laryngol ; 93(6 Pt 1): 595-9, 1984.
Artigo em Inglês | MEDLINE | ID: mdl-6508132

RESUMO

Abnormal vestibular function disrupts postural and ocular muscle control system references to gravity (earth) vertical. Vestibular disorders also prevent satisfactory resolution of normally redundant, but often conflicting, visual and somatosensory spatial references required for normal postural control during active and passive body motion. Using a moving platform and visual surrounds posturography technique to systematically interact visual, somatosensory, and vestibular inputs, it was clearly demonstrated that patients with the benign paroxysmal positional nystagmus type of distorted vestibular function employ an unstable, visually dependent postural sway distinct from the postural instability associated with unilateral or bilateral vestibular functional deficits. These findings have important clinical implications for diagnosis and management of patients with vestibular disorders.


Assuntos
Nistagmo Patológico/fisiopatologia , Postura , Vertigem/fisiopatologia , Adulto , Fatores Etários , Fixação Ocular , Humanos , Doenças do Labirinto/fisiopatologia , Pessoa de Meia-Idade , Orientação , Propriocepção , Rotação , Percepção Visual
20.
Acta Otolaryngol Suppl ; 406: 110-4, 1984.
Artigo em Inglês | MEDLINE | ID: mdl-6332451

RESUMO

Abnormal vestibular function disrupts a subject's reference to gravity (earth) vertical, and prevents resolution of conflicting or inaccurate visual and somatosensory spatial references. However, errors which patients make when attempting to resolve conflicting visual and somatosensory orientation inputs during upright stance differed markedly in patients with (1) symmetric or asymmetric reduced vestibular function, (2) benign paroxysmal positional nystagmus and vertigo, and (3) a combination of distorted and reduced function. Objective characterization of spatial orientation systems and compensatory strategies under altered sensory conditions is an essential first step toward identifying optimal treatment methods for each of these three types of vestibular deficient patients.


Assuntos
Nistagmo Patológico/fisiopatologia , Medula Espinal/fisiologia , Vertigem/fisiopatologia , Nervo Vestibular/fisiologia , Vestíbulo do Labirinto/fisiopatologia , Humanos , Doenças do Labirinto/fisiopatologia , Postura , Testes de Função Vestibular
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