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At least 307 records · Page 17Linked to original sources
PubMed1999

Postural control of ballet dancers: a specific use of visual input for artistic purposes.

Dance is a specific expression of human motor behaviour. This artistic physical activity depends upon an effective technical training with important postural components and necessitates the codification of sensory inputs to build mental representations of the action to be produced. Proprioception and vision being two fundamental sensory modalities in classical ballet, this study attempted to determine the importance of the visual input for postural control during the practice of this activity. First, this work compared the performances of 18 professional ballet dancers and 46 non-dancers on a platform of forces during static posturographic tests in open or closed eyes situation. Then, we studied how professional dancers achieve balance in postures specific of classical ballet: on demi-pointe and on pointe. The results indicate that visual inputs are important in classical ballet since dancers only performed better than controls in eyes open conditions. The similar results obtained on pointe with eyes open or closed conversely suggest that training in classical ballet develops specific modalities of balance which are not transferable to posture control in daily life situations.

Adolescent↗
PubMed1998

Postural control, attention and sleep deprivation.

We investigated the effect of sleep deprivation on postural control during a simple reaction time task (SRT), during a task requiring the intermittent inhibition of a reaction (IRT), and in the absence of a concurrent information processing task. Postural sway, i.e. changes in center of pressure on a force platform, was recorded in three increasingly difficult standing conditions (fixed platform, sway-referenced platform and sway-referenced platform with sway-referenced visual scene) during the three information-processing task conditions. Five healthy subjects performed the tasks either after normal sleep or following 24 h of sustained wakefulness. As hypothesized, sleep deprivation significantly increased postural sway only in the IRT condition. Within the IRT condition, sleep deprivation significantly increased sway across all postural conditions.

Adult↗
PubMed2005

Improved postural control through repetition and consolidation.

Research regarding the optimal frequency of training in postural control rehabilitation has been sparse. Posturography with vibratory proprioceptive stimulation was performed with eyes open and closed on 36 healthy subjects divided into 3 groups. Each group was tested 5 times, though with different time-intervals; 20 minutes, 3 hours and 24 hours respectively. Two different adaptive processes seems to be involved in the formation of a new movement pattern when exposed to a postural disturbance, one fast adaptation active during each test occasion and a second adaptation active between the consecutive tests. As the same adaptation pattern was found regardless the repetition time interval, the results imply either that the consolidation process of the new motor memory is time-independent or that the stimulus was sufficiently strong to induce fast consolidation thus leaving the time-interval unimportant. The findings suggest that it is primarily the number of repetitions in the exercises that governs the outcome of training, whereas the time interval between the exercises is of less importance.

Adaptation, Psychological↗
PubMed2005

Undisturbed upright stance control in the elderly: Part 2. Postural-control impairments of elderly fallers.

A common way of predicting falling risks in elderly people can be to study center of pressure (CP) trajectories during undisturbed upright stance maintenance. By estimating the difference between CP and center of gravity (CG) motions (CP - CGv), one can estimate the neuromuscular activity. The results of this study, which included 34 sedentary elderly persons aged over 75 years (21 fallers and 13 nonfallers), demonstrated significantly increased CGh and CP - CGv motions in both axes for the fallers. In addition, the fallers presented larger CGh motions in the mediolateral axis, suggesting an enlarged loading-unloading mechanism, which could have reflected the adoption of a step-initiating strategy. As highlighted by fractional Brownian motion modeling, the distance covered by the CP - CGv motions before the successive control mechanisms switched was enhanced for the fallers in both axes, therefore increasing the risk that the CG would be outside of the base of support.

Accidental Falls↗
PubMed2002

Comparative neurobiology of postural control.

In recent years, studies of nervous mechanisms for the control of body posture have been performed on animal models of different complexity - cat, rabbit, lamprey and the mollusc Clione. These studies have greatly expanded our knowledge of how the control system operates, how the system can change the stabilized body orientation and how the postural functions are distributed within different parts of the CNS. For simpler animal models, the postural network has been analyzed in considerable detail and main cell types and their interactions have been identified.

Anatomy, Comparative↗
PubMedDate not supplied

Indicators of the influence a peripheral vestibular deficit has on vestibulo-spinal reflex responses controlling postural stability.

For a controlled sway stabilization task, the areas underlying EMG responses in ankle and neck muscles, as well as amplitudes of ankle torque responses, were shown to be significantly correlated with the clinically defined extent of a patient's peripheral vestibular deficit. The responses, elicited by ankle dorsiflexion of the support surface on which the subject stood, were statistically examined in order to select those measurements which would best indicate differences between a normal, a patient with a unilateral deficit, or one with a bilateral deficit. For this purpose, a stepwise discriminant analysis was performed on measurements of head and trunk angular accelerations in addition to muscle EMG and ankle torque signals. The primary measurements selected to optimally assign a subject to a population were the periods of ankle torque and neck extensor activity associated with correcting for the imposed body displacement backwards and maintaining upright head position respectively. The resulting division into populations was 100% correct. However, within the population of unilateral deficit patients, the technique failed to correctly identify those with acute from those with compensated deficit. This technique of investigating vestibulo-spinal reflex responses is more specific and sensitive than Romberg tests, because it will quantify and specify the underlying cause of the patient's balance and ambulatory disorder.

Adult↗
PubMed2004

Effect of preparation on dual-task performance in postural control.

The authors applied an overlapping-task design to study the interaction between postural control and cognitive task processes in young (n = 10) and older (n = 10) adults. A rapid destabilizing floor translation was followed at specific time intervals by a simple auditory reaction time (RT) task. The translations were preceded by either an informational cue or no cue. Interference between postural task demands and the RT task was found only in the first 50 ms. Cueing also had an effect on both the onset of the postural recovery response and RT performance. The results suggest (a) only a brief interference between postural and cognitive processing demands in relatively easy tasks, (b) competition for a common central mechanism, possibly a response-selection mechanism, and (c) no differential impact of aging on that interaction.

Adult↗
PubMedDate not supplied

Age-related changes in human posture control: motor coordination tests.

Postural responses to support surface displacements were measured in 214 normal human subjects ranging in age from 7 to 81 y. Motor tests measured leg muscle electromyographic (EMG) latencies, body sway, and the amplitude and timing of changes in center of pressure displacements in response to sudden forward and backward horizontal translations of the support surface upon which the subjects stood. There were small increases in both EMG latencies and the time to reach the peak amplitude of center of pressure responses with increasing age. The amplitude of center of pressure responses showed no change with age if the amplitude measures were normalized by a factor related to subject height. In general, postural responses to sudden translations showed minimal changes with age, and all age-related trends that were identified were small relative to the variability within the population.

Adolescent↗
PubMed2003

Influences of illusionary position perception on anticipatory postural control associated with arm flexion.

We examined the effect of illusionary perception on anticipatory postural control associated with arm flexion with subjects in a standing position, using vibration stimulation of the Achilles' tendon. Arm flexion was performed five times under each of the following conditions: (1) quiet standing, (2) vibration of the Achilles' tendon at 100 Hz frequency and 1.5 mm amplitude with the trunk fixed by a stopper during quiet standing, and (3) a perceived standing position during vibration. The reproduced positions were located forward by about 20% of the foot length compared with the quiet standing position; these positions showed no significant differences among the five trials. In the first trial of arm flexion during vibration, the biceps femoris began activating approximately 40 ms before the anterior deltoid. The same time difference between activation of the two muscles was observed in the reproduced condition. As the vibration trials were repeated, this activation timing approached the value in the quiet standing condition. In both the biceps femoris and erector spinae, the mean amplitude of electromyogram for the first 50 ms after the start of activation did not differ significantly among the three conditions.

Achilles Tendon↗
PubMed2000

The effect of age on the attentional demands of postural control.

A dual-task paradigm was used to determine the attentional demands of several postural control tasks in 16 older women (age, 71.5+/-3.4 years) and 14 young women (age, 25.5+/-2.4 years). Older women had slower verbal reaction times (VRT) compared with the younger women and increased reaction time more from a sitting to standing posture. Compared with the younger women, older women required more cognitive resources to maintain a simple eyes open standing posture versus an eyes open seated posture. Further, older women had significantly greater VRT during the dual-task conditions compared with younger women. However, VRT did not significantly change as the difficulty of the primary task increased in either group. These data have implications for older adults who may be at risk for falls in situations where they may be engaged in concurrent tasks, even when those tasks are considered automated and/or lower order operations.

Accidental Falls↗
PubMed2001

Characteristics of somatosensory feedback in postural control during standing.

In the present study, the function of the somatosensory feedback system in postural control was investigated. For the sake of simplicity, the present study considered only balancing in the anteroposterior direction using the ankle strategy, in which the ankle moment is mainly used to maintain balance. To suppress the vestibular and visual feedback paths, a subject stood on a force-measuring platform with a fixed back support. Because the subject's body was immovable under these conditions, the subject controlled a computer model that simulated the subject's load at the ankles. Information about the sway angle of the model was fed through the somatosensory feedback path. Frequency response functions of the ankle moment in response to the sway angle were calculated. The experimental results suggest that the human somatosensory feedback system has derivative characteristics and, consequently, can maintain an upright posture by itself. The results were compared with those of previous studies on vestibular and visual feedback systems. The comparison reveals that subject-to-subject variance in the somatosensory system is significantly smaller than that in the other systems. This may indicate that the somatosensory feedback is the most automatic of the systems and plays a dominant role when a subject maintains an upright posture using the ankle strategy.

Adult↗
PubMed1996

Availability of visual and proprioceptive afferent messages and postural control in elderly adults.

The ability of young and elderly adults to keep a stable upright posture while facing changes in the availability of visual and/or propriomuscular information was investigated. The two sensory sources of information were alternatively available and withdrawn, jointly and separately, during 10-s alternating sequences. Vision was modified by means of liquid-crystal goggles, and proprioception was altered by means of tendon vibration of both antagonistic ankle muscles. Elderly adults were less stable than young adults when vision was withdrawn. Both groups were greatly affected when propriomuscular inputs were altered by vibration. Under constant visual conditions and following a propriomuscular perturbation (i.e., vibration), elderly adults were unable to take advantage of the reinsertion of propriomuscular inputs. They showed a transient, decreased stability and were unable to fully recover during a 10-s period, whereas young adults were able to rapidly integrate the information to stabilize their posture. When both propriomuscular and visual inputs were withdrawn and concurrently reinserted, the elderly adults did not show a transitory increase in the velocity of the center of foot pressure. The present results extend findings on the inability of elderly adults to reconfigure rapidly the postural set following reinsertion of sensory inputs. The results also suggest that elderly adults have difficulties in taking advantage of sensory redundancy in postural control.

Adult↗
PubMedDate not supplied

A multi-purpose rehabilitation frame: an apparatus for experimental investigations of human balance and postural control.

Moving and rotating platforms are often used in experimental investigations of human balance and postural control. These devices are not well suited for testing elderly and neurologically impaired individuals, because of inherent risk of injury to the experimental subject due to a potential fall. This paper describes a novel mechanical apparatus that generates perturbations to a standing subject by applying pushing forces at the level of the pelvis and can also provide restoring forces in the case of destabilization. The device has two degrees of freedom, which are actuated by hydraulic servo systems, and can deliver a perturbation in any direction comprised within anterio-posterior and medio-lateral postural space. The accuracy and repeatability of the perturbations elicited in eight different directions was evaluated. The results, showing a high degree of correlation between the trajectories in both degrees of freedom of the apparatus, demonstrate that accurate and repeatable perturbations can be imposed on the subjects tested.

Biomechanical Phenomena↗
PubMed1991

Whiplash, postural control, and the inner ear.

Many patients with "whiplash syndrome" experience unrelenting neck stiffness and pain. This abnormal muscular tension is postulated to be causally related to a central disorder of postural control, which has evolved secondary to injury of the inner ear labyrinthine structures. Moving platform posturography was used to demonstrate the presence or absence of a static or dynamic equilibrium disorder in 48 patients who had experienced the oscillation forces induced by a rear-end automobile collision. Other vestibular tests were used to document dysfunction of the semicircular canals and the otolith structures. A high percentage of patients were found to have faulty inner ear functioning leading to inefficient muscular control of balance and erect posture. Active perilymph fistulas were identified at surgery in seven patients.

Adult↗
PubMed2005

Development of postural control during the first 18 months of life.

The present paper reviews the development of postural adjustments during infancy. In the control of posture, two functional levels can be distinguished. The basic level deals with the generation of direction-specific adjustments, meaning that dorsal muscles are primarily activated when the body sways forward, whereas ventral muscles are primarily activated when the body sways backward. The second level is involved in adaptation of the direction-specific adjustments. Postural development starts with a repertoire of direction-specific adjustments suggesting that the basic level of control has an innate origin. At first, during the phase of primary variability, postural activity is largely variable and can be minimally adapted to environmental constraints. At 3 months, postural activity shows a transient period during which few postural muscles participate in postural activity. From 6 months onward, the phase of secondary variability starts, during which the second level of postural control becomes functionally active and infants develop the ability to adapt postural activity to the specifics of the situation. Initially, adaptation can be accomplished in a simple way only, but from 9-10 months onward, it can be performed by the subtle adaptation of the degree of muscle contraction. Around 13-14 months, anticipatory postural adjustments emerge. It is concluded that the development of postural adjustments is characterized by four periods of transition occurring at the ages of 3, 6, 9-10, and 13-14 months. The major transition occurs at 6 months, when infants move from the phase of non-adaptive, primary variability to the phase of adaptive, secondary variability.

Adaptation, Physiological↗
PubMed2003

Neck muscle fatigue affects postural control in man.

We hypothesised that, since anomalous neck proprioceptive input can produce perturbing effects on posture, neck muscle fatigue could alter body balance control through a mechanism connected to fatigue-induced afferent inflow. Eighteen normal subjects underwent fatiguing contractions of head extensor muscles. Sway during quiet stance was recorded by a dynamometric platform, both prior to and after fatigue and recovery, with eyes open and eyes closed. After each trial, subjects were asked to rate their postural control. Fatigue was induced by having subjects stand upright and exert a force corresponding to about 35% of maximal voluntary effort against a device exerting a head-flexor torque. The first fatiguing period lasted 5 min (F1). After a 5-min recovery period (R1), a second period of fatiguing contraction (F2) and a second period of recovery (R2) followed. Surface EMG activity from dorsal neck muscles was recorded during the contractions and quiet stance trials. EMG median frequency progressively decreased and EMG amplitude progressively increased during fatiguing contractions, demonstrating that muscle fatigue occurred. After F1, subjects swayed to a larger extent compared with control conditions, recovering after R1. Similar findings were obtained after F2 and after R2. Although such behaviour was detectable under both visual conditions, the effects of fatigue reached significance only without vision. Subjective scores of postural control diminished when sway increased, but diminished more, for equal body sway, after fatigue and recovery. Contractions of the same duration, but not inducing EMG signs of fatigue, had much less influence on body sway or subjective scoring. We argue that neck muscle fatigue affects mechanisms of postural control by producing abnormal sensory input to the CNS and a lasting sense of instability. Vision is able to overcome the disturbing effects connected with neck muscle fatigue.

Adult↗
PubMedDate not supplied

Are the changes in postural control associated with low back pain caused by pain interference?

BACKGROUND: Voluntary limb movements are associated with involuntary and automatic postural adjustments of the trunk muscles. These postural adjustments occur prior to movement and prevent unwanted perturbation of the trunk. In low back pain, postural adjustments of the trunk muscles are altered such that the deep trunk muscles are consistently delayed and the superficial trunk muscles are sometimes augmented. This alteration of postural adjustments may reflect disruption of normal postural control imparted by reduced central nervous system resources available during pain, so-called "pain interference," or reflect adoption of an alternate postural adjustment strategy. METHODS: We aimed to clarify this by recording electromyographic activity of the upper (obliquus externus) and lower (transversus abdominis/obliquus internus) abdominal muscles during voluntary arm movements that were coupled with painful cutaneous stimulation at the low back. If the effect of pain on postural adjustments is caused by pain interference, it should be greatest at the onset of the stimulus, should habituate with repeated exposure, and be absent immediately when the threat of pain is removed. Sixteen patients performed 30 forward movements of the right arm in response to a visual cue (control). Seventy trials were then conducted in which arm movement was coupled with pain ("pain trials") and then a further 70 trials were conducted without the pain stimulus ("no pain trials"). RESULTS: There was a gradual and increasing delay of transversus abdominis/obliquus internus electromyograph and augmentation of obliquus externus during the pain trials, both of which gradually returned to control values during the no pain trials. CONCLUSION: The results suggest that altered postural adjustments of the trunk muscles during pain are not caused by pain interference but are likely to reflect development and adoption of an alternate postural adjustment strategy, which may serve to limit the amplitude and velocity of trunk excursion caused by arm movement.

Abdominal Muscles↗