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PubMed1998

Postural adjustments accompanying fast pointing movements in standing, sitting and lying adults.

The present study evaluated the effect of different positions, which varied in the amount of bodily support, on postural control during fast pointing movements. Fourteen adult subjects were studied in standing, various sitting and lying positions. Multiple surface electromyograms (EMGs) of arm, neck, trunk and upper leg muscles and kinematics were recorded during a standard series of unilateral arm movements. Two additional series, consisting of bilateral arm movements and unilateral arm movements with an additional weight, were performed to assess whether additional task-load affected postural adjustments differently in a sitting and standing position. Two pointing strategies were used--despite identical instructions. Seven subjects showed an elbow extension throughout the movements. They used the deltoid (DE) as the prime mover (DE group). The other seven subjects performed the movement with a slight elbow flexion and used the biceps brachii (BB) as the prime mover (BB group). The two strategies had a differential effect on the postural adjustments: postural activity was less and substantially later in the BB-group than in the DE group. Anticipatory postural muscle activity was only present in the DE group during stance. In all positions and task-load conditions the dorsal postural muscles were activated before their ventral antagonists. The activation rate, the timing and--to a lesser extent the amplitude of the dorsal muscle activity was position dependent. The position dependency was mainly found in the caudally located lumbar extensor (LE) and hamstrings (HAM) muscles. The EMG amplitude of LE and HAM was also affected by body geometry (trunk and pelvis position). Position and body geometry had only a minor effect on the activity of the neck and thoracic extensor muscles. This difference in behaviour of lower and upper postural muscles suggests that they could serve different postural tasks: the lower muscles being more involved in keeping the centre of mass within the limits of the support surface, and the upper ones in counteracting the reaction forces generated by movement onset. Increasing task-load by performing bilateral movements and--to a minor extent--during loaded unilateral movements affected the temporal and quantitative characteristics of the postural adjustments during standing and sitting in a similar way. The effect was present mainly during the early part of the response (within 100 ms after prime mover onset). This suggests that feedforward or anticipatory mechanisms play a major role in the task-specific modulation of postural adjustments.

Adaptation, Physiological↗

PubMed2002

The Romberg sign and early instruments for measuring postural sway.

In the first half of the 19th century, European physicians-including Marshall Hall, Moritz Romberg, and Bernardus Brach-described loss of postural control in darkness of patients with severely compromised proprioception. Romberg and Brach emphasized the relationship between this sign and tabes dorsalis. Later, other neurologists evaluated the phenomenon, which is now known as Romberg's sign, in a broader range of neurologic disorders using a variety of simple but increasingly precise and sensitive clinical tests. In the late 19th century, neurologists also developed instruments to measure and record postural sway in patients with neurologic disease. Principal contributors included Philadelphia neurologist Silas Weir Mitchell and his trainees Morris Lewis and Guy Hinsdale. The efforts of these neurologists anticipated later physiologic studies and ultimately the development of computerized dynamic platform posturography.

Diagnostic Equipment↗

PubMed1987

Evaluation of autonomic dysfunction in familial dysautonomia by power spectral analysis.

We examined the nature and extent of the autonomic control defect in patients with autonomic dysfunction using power spectral analysis of heart rate fluctuations. Heart rate variability and respiratory patterns were monitored and discrete blood pressure measurements were made during supine and standing positions in 10 ambulatory patients with familial dysautonomia and in controls. Postural hypotension without compensatory tachycardia was confirmed in the patients upon standing. The balance between sympathetic and parasympathetic activity was compared in both positions by quantifying the power of the low (0.04-0.095 Hz) and high (respiratory) frequency fluctuations in instantaneous heart rate. After changing from supine to standing position there was a small decrease in the low frequency power of heart rate fluctuations in the patients as opposed to a significant increase in controls. The mean power of fluctuations occurring at high frequency decreased only slightly in the patients compared to a marked decrease in the controls. We conclude that the fall in blood pressure, lack of appropriate heart rate modulation, and failure to increase low frequency heart rate power which occurred in the patients upon standing, are all due to lack of increased sympathetic output under the influence of gravity. The failure to decrease power in the respiratory frequency peak in the patients, suggests an abnormal retention of parasympathetic activity. This may be explained by parasympathetic compensation for the substantial sympathetic loss, or by a lack of appropriate inhibition of parasympathetic tone from baroreceptors or supraspinal structures.

Adult↗

PubMed2003

Development of postural adjustments during reaching in sitting children.

We evaluated the development of postural adjustments accompanying reaching movements in sitting children. Twenty-nine typically developing children aged, 2-11 years, and ten adults were studied with multiple surface electromyograms (EMGs) and kinematics during reaching in four conditions: sitting with the seat-surface oriented horizontally with and without an additional task load, and sitting with the seat-surface tilted 15 degrees forward and 15 degrees backward. The development of postural adjustments during reaching in a sitting position turned out to have a non-linear and protracted course, which is not finished by the age of 11 years. The development of these adjustments is characterised by variation, yet specific developmental sequences could be distinguished. Firstly, the development of postural adjustments during reaching from the age of 2 years onwards lacked a preference for an en bloc strategy, which consists of an in concert activation of the direction-specific neck and trunk muscles. Secondly, anticipatory postural muscle activity, which was consistently present in adults, was virtually absent between 2 and 11 years of age. Thirdly, the data demonstrated that with increasing age the head gradually becomes the dominant frame of reference. In addition, the study suggested that, in terms of postural control, the forward-tilted position is the most efficient one.

Adult↗

PubMed2005

Balance and fear of falling in Parkinson's disease.

To assess internal consistency and validity of measures of balance (Berg balance scale, BBS), postural changes (postural changes scale, PCS) and fear of falling (fear of fall measure, FFM) in 70 ambulant Parkinson's disease (PD) persons, these instruments were matched with performance-based balance and mobility tests, and other clinical, functional and quality of life PD-specific measures. The BBS, PCS and FFM showed a good internal consistency, moderate to good inter-correlation, and a significant correlation with measures of both disability (UPDRS-ADL, Schwab and England scale) and--to a lesser extent--impairment/severity of symptoms (UPDRS-ME, Hoehn and Yahr Scale). Tandem Romberg, Single-Limb Stance, Functional Reach, and the Timed Up & Go test correlated slightly better with BBS than with PCS and FFM. This study shows that problems of balance and postural control in PD patients result from complex interactions between motor impairment, functional abilities and fear of falling.

Accidental Falls↗

PubMed1995

Programmatic vestibular rehabilitation.

Although the use of vestibular exercises for patients with persistent vertigo and dysequilibrium has received some attention for many years, organized vestibular rehabilitation therapy programs have only recently been introduced. The benefits of such programs are becoming widely accepted. They typically involve a three-pronged approach: habituation exercises designed to facilitate central nervous system compensation by extinguishing pathologic responses to head motion, postural control exercises, and general conditioning activities. This article will describe the programmatic approach to vestibular rehabilitation, emphasizing selection criteria and reviewing results that may be anticipated when this treatment modality is used in a variety of patient populations.

Humans↗

PubMed1991

[Postural motility and cognitive functions in children with dyspraxia].

As many as 58 children aged 5.6 to 13.6 years with dyspraxia were examined. The tone of musculature, the psychomotor system (postural control, coordination of movements, lateralization of body perception) and cognitive functions were explored. Dissociation of the lateralization of the tone and motor functions together with spatial thinking deficiency were established.

Adolescent↗

PubMed1999

Postural adjustments during spontaneous and goal-directed arm movements in the first half year of life.

We studied the development of postural control during goal-directed reaching and spontaneous arm movements in early infancy. Two groups of infants participated. The first group consisted of 10 healthy infants, who were assessed four times at the ages of 3, 4, 5 and 6 months. Each assessment consisted of simultaneous recording of video-data and surface EMGs of arm, neck, trunk, and leg muscles in various lying and sitting positions. Additionally, postural adjustments during spontaneous arm movements were studied in a second group of five infants aged 1-3 months. Already before the onset of successful reaching, which occurred at 4 5 months, both spontaneous and goal-directed arm movements were accompanied by a high amount of postural activity. During the goal-directed arm movements a preference for neck muscle activation and a direction specific organisation (dorsal postural muscles activated before the ventral antagonists) prevailed, whereas during spontaneous arm movements such a specific postural organisation was absent. With increasing age and concurrent with successful reaching, the amount of postural activity decreased. Still, the persisting postural activity continued to become more organised with increasing age. Position affected the postural adjustments accompanying goal-directed arm movements at all ages.

Arm↗

PubMed1995

Age effects on reflex and postural responses to propriomuscular inputs generated by tendon vibration.

The effects of aging on two sensorimotor levels of propriomuscular function were investigated in a young (20- to 44-year-old) and an elderly (60- to 86-year-old) population by eliciting segmental reflex and postural responses via the same muscle spindle inflow generated by applying the same pattern of tendon vibration. The latency and amplitude of the reflex responses to vibration (tonic vibration reflex) of the biceps and triceps brachii did not depend on the subjects' age. No major age-related changes were observed in the deep reflexes of the lower limbs. The postural responses to the same vibratory stimulation applied to both the soleus or the tibialis anterior muscles (vibration-induced falling) did not show any changes in latency depending on either age or the visual conditions, whereas the intensity of these responses decreased both with age and when the use of vision was possible. Our results suggest that the two levels at which the same propriomuscular messages were processed are differentially affected by aging. The lower reflex level does not undergo any noticeable impairment, whereas the higher postural control level deteriorates in the elderly, which might be partly responsible for the balance problems which tend to occur more frequently with advancing age.

Adult↗

PubMed1994

Gender differences in the balance of healthy elderly as demonstrated by dynamic posturography.

BACKGROUND: Prior studies indicate that older women fall more often than men although there is no evidence of gender-based balance differences. Using a force platform, we measured the effects of restricted sensory input and support surface movement to detect gender differences in balance. METHODS: Healthy, elderly community dwellers (N = 234, mean age = 76 +/- 5 years, 52% female) were administered the following perturbations on the balance platform: The platform and/or visual surround were fixed or tilted proportionally to the subject's sway with the eyes open or closed, forward or backward horizontal translations, and toes-up and toes-down rotations. RESULTS: Gender-based balance differences were not present during quiet standing, or when the support surface or visual input were manipulated separately. Women swayed and lost their balance more than men when the surface was sway-referenced while vision was compromised, but by the third trial their sway control was comparable to the men. Women also initially lost their balance more frequently than men during toes-up and -down rotations, and compared to men continued to lose their balance more often during repeated toes-up rotations. Finally, women developed less angular momentum than men in response to forward platform rotations. DISCUSSION: Elderly women show impairments of balance when simultaneously deprived of visual and somatosensory inputs or during a backwards destabilization. Since there is little evidence for a CNS source for such gender differences, biomechanical origins (e.g., dorsiflexion strength and range of motion) are a more likely cause. Limited postural control of women under conditions stressing balance may explain their greater frequency of falling.

Adaptation, Physiological↗

PubMed2001

Tai chi: physiological characteristics and beneficial effects on health.

OBJECTIVES: To assess the characteristic effects of Tai Chi Chuan (TCC) exercise on metabolism and cardiorespiratory response, and to measure its effect on cardiorespiratory function, mental control, immune capacity, and the prevention of falls in elderly people. DESIGN: A review of controlled experimental studies and clinical trials designed with one of two aims: either to assess physiological responses during the performance of TCC or to assess the impact of this exercise on general health and fitness. MAIN OUTCOME MEASURES: Metabolic rate, heart rate, blood pressure, ventilation, maximal oxygen uptake (VO(2)MAX), immune capacity, falls, and fall related factors. SUBJECTS: A total of 2216 men and women. RESULTS: Under review were 31 original studies, published in Chinese or English journals, that met the criteria for inclusion. Most of the papers written in Chinese had not been introduced into the Western literature. Nine of these studies showed that TCC can be classified as moderate exercise, as its does not demand more than 55% of maximal oxygen intake. When this form of exercise and others conducted at equal intensity were compared, TCC showed a significantly lower ventilatory equivalent (VE/VO(2)MAX). Evidence provided by cross sectional and longitudinal studies suggests that TCC exercise has beneficial effects on cardiorespiratory and musculoskeletal function, posture control capacity, and the reduction of falls experienced by the elderly. CONCLUSIONS: TCC is a moderate intensity exercise that is beneficial to cardiorespiratory function, immune capacity, mental control, flexibility, and balance control; it improves muscle strength and reduces the risk of falls in the elderly.

Accidental Falls↗

PubMed2005

Effect of age on body sway assessed by computerized posturography.

The swaying and postural instability frequently seen in elderly subjects had not been analyzed quantitatively in detail until the introduction of computerized posturography. In order to assess the changes of body sway with aging, we performed computerized posturography in 144 subjects (51 men and 93 women, between the ages of 22 and 88 years) without specific neurological or metabolic disorders. The total and timed track length of the center of gravity, reflecting the distance of sway, increased with advancing age, with a highly significant positive correlation, without marked sex differences. The total area covered by the track of the center of gravity (expressing the extent of sway) also showed a similar tendency. Track density per unit area, expressing the efficiency of postural control, in contrast, decreased with age, showing a significant negative correlation with age, but only when the subjects had their eyes open; this decrease did not occur when they had their eyes closed. The Romberg ratio, an index of exacerbation of sway on eye closure, showed little change with a tendency for slight alleviation of sway and improvement in the efficiency of its control. Computerized posturography appears to be a useful tool with which to analyze the mechanism of swaying associated with old age.

Adult↗

PubMed1999

Support stability influences postural responses to muscle vibration in humans.

We studied the effect of support stability on postural responses to the vibration of Achilles tendons and of neck dorsal muscles in healthy humans. For this purpose we compared postural responses on a rigid floor and on 6 cm high rocking supports (see-saws) of different curvatures (different radii: 30, 60 and 120 cm). The subject stood with eyes closed, the centre of the feet coincided with the centre of the see-saw. We recorded platform tilt, horizontal displacements of the upper body, ankle joint angle and activity of ankle joint muscles. On the rocking platform subjects maintained balance in a sagittal direction by making see-saw rotations placing the support under the body's centre of gravity. Equilibrium maintenance requires that the torque in the ankle joint increases during forward body displacements, as on the rigid floor, and be accompanied by a plantar flexion (not by a dorsiflexion) in the ankle joint. The directional dependence of vibration-induced reactions on the see-saw was the same (relative to space) as on the rigid floor: backward body displacement during Achilles tendon vibration and forward body displacement during neck muscle vibration. A decrease of support stability (with a decrease of the radius from 120 to 30 cm) diminished significantly the effect of Achilles tendon vibration and to a lesser extent the effect of neck muscle vibration. In contrast, the increase of platform stability by hand contact with a stable external object gave rise to prominent body sway in response to Achilles tendon vibration. Neck muscle vibration on the movable support provoked a quick initial forward body sway. This initial quick response was absent during vibration of the Achilles tendons. We conclude that postural responses to muscle vibration reflect the participation of different muscles in posture control and depend on the support properties. Support instability changes the role of proprioceptive information and the state of the system of equilibrium maintenance.

Achilles Tendon↗

PubMed2006

The mobility capabilities of persons with adolescent idiopathic scoliosis.

STUDY DESIGN: An analysis of differences among healthy elementary school children and those with adolescent idiopathic scoliosis (AIS), and between groups of individuals with AIS with different Cobb angles. OBJECTIVES: To research the differences in dynamic balance among adolescents with a variety of postural statuses and verify the sensitivity value of the Cobb angle. SUMMARY OF BACKGROUND DATA: Assuming the biomechanical and functional particularities of the children with AIS, there is a need for an earlier diagnosis. METHODS: The participants' balance (left and right step test) was estimated using electromyography and the reaction of base power on the platform. RESULTS: Discriminant analysis confirmed a significant difference between the participants with AIS and healthy persons on the left step test. The values of the lumbal erector muscles, right gluteus, and side-to-side reaction of the force platform are more pronounced than the other variables. There is no significant difference among the participants with various Cobb angles. CONCLUSIONS: The dynamic balance tests contribute to the AIS screening process. The pathologic form of AIS and lateralization highly affect dynamic balance. The study confirmed the neurophysicians' claims of the neuroplasticity of the central nervous system. In addition, the research illustrated the compensational functioning of mobility, especially when there is a lack of normal mobility forms, and there are weak postural control mechanisms and proprioception. There was no proof of the value of the Cobb angle as a clinical method and a measurement of the functional capabilities of the participants in the screening process.

Adolescent↗

PubMed1996

Update on vestibular rehabilitation therapy.

Although the concept of using exercises as part of the treatment for patients with persistent vertigo was introduced several decades ago, organized vestibular rehabilitation therapy programs have only recently been introduced. These programs typically involve a three-pronged approach, customized to the needs of the individual patient: (1) habituation exercises designed to facilitate central nervous system compensation by extinguishing pathologic responses to head motion, (2) postural control exercises, and (3) general conditioning activities. This article provides an update regarding the status of vestibular rehabilitation, reviewing the concept of vestibular compensation and patient selection criteria for current rehabilitative techniques.

Adaptation, Physiological↗

PubMed1996

Long-term effects of antidepressants on balance, equilibrium, and postural reflexes.

To assess the long-term effects of antidepressant medication on balance, equilibrium, and postural reflexes, we studied 30 patients, ages 20-76 years, who had a diagnosis of depressive disorder (as defined by DSM-III-R criteria) and had been treated with tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs) for > or = 1 year. They were assessed by a Balance Master System. The assessment included three tasks: static balance, rhythmic weight shift, and limits of stability. When compared with 30 nonhospitalized healthy controls (of comparable age and the same sex), patients who took TCAs showed impaired balance function in all main indices. The results suggest that the impairment of balance function includes motor coordination, fine-motor control, postural reflexes, maintaining equilibrium, and reaction time. No obvious impairment of balance function was observed in patients who took SSRIs.

Adult↗

PubMed2005

Postural dysfunction in children with cerebral palsy: some implications for therapeutic guidance.

Postural problems play a central role in the motor dysfunction of children with cerebral palsy (CP). Therefore, they spend more time in sitting than in standing to perform vital tasks of daily life. The focus of this article is to describe the pathophysiology of postural control in sitting and outline some implications for management and treatment. In general, children with CP exhibit muscular activity counteracting forces that disturb equilibrium. Only 'non-sitting' children with severe CP lack such 'direction-specific' adjustments, possibly ruling out achievement of independent sitting. Most frequently, the children display dysfunctions in the adaptation of the adjustment. Typical characteristics of this adaptation in children with CP are a top-down recruitment of postural muscles, an excessive degree of antagonistic coactivation, and an incomplete adaptation of the EMG-amplitude to task specific constraints. Despite our knowledge on the pathophysiology underlying the postural problems in children with CP, little 'high-level' evidence (according to Sackett) exists on how different interventions can affect these problems. Therapeutic attention to promote motor performance in sitting focuses on adaptive seating, tilting of the support surface, and ample, variable training in motivating settings. The challenge facing us now is to provide evidence about the efficacy of specific treatment approaches facilitating that children reach an optimal level of functioning in daily life.

Cerebral Palsy↗

PubMed2001

[Postural and locomotor evaluation of normal pressure hydrocephalus: a case report].

Generally, the diagnosis of idiopathic normal pressure hydrocephalus (NPH) is raised in elderly patients with an association of gait disturbances, cognitive impairment, urinary incontinence and widening of the ventricles. Gait disturbances appear as the predominant clinical symptom of NPH, and may precede other symptoms. The main objectives of this study were to determine the effect of ventriculoperitoneal shunt (VPS) on gait and to compare the results obtained in HPN with those obtained in Parkinson's disease (PD). The performance of a patient with NPH on specific postural and locomotion tasks was analyzed during three successive experimental sessions: the first one before VPS, the second one week after VPS and the third three months after VPS. The patient was instructed to walk at his natural speed and also to maintain postural control for one minute. Four gait parameters (mean velocity, stride length, cadency and step width) were calculated for each session to assess the subject's performance. In this NPH patient there was a significant improvement in gait performance before and after VPS. This improvement concerned mean velocity, stride length and step cadency but did not involve the width component which remained unchanged. Before VPS, the NPH patient walked slower and with a shorter stride length than a group of patients with PD. After VPS his performance was better than the PD group except for cadency. Step width remained longer for the HPH patient than in PD patients for all three sessions. From this study, it appears that gait in idiopathic NPH exhibits a specific temporospatial pattern distinct from that in PD or normal age-matched controls. Changes in gait can be evaluated shortly after treatment of NPH. Gait disorders, excepting dynamic balance, may normalize as soon as one week after surgery.

Aged↗