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Results for “Postural Balance”

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PubMed2006

Synergistic muscle activation during maximum voluntary contractions in children with and without spastic cerebral palsy.

We examined muscle recruitment patterns in children with cerebral palsy (CP) and comparison children without CP under conditions of maximum voluntary contractions. Three groups of children participated in the study: (1) 12 children with diplegic CP (eight males, four females; age range 4-10 y, mean age 7 y [SD 2 y 4 mo]); (2) six children with hemiplegic CP (four males, two females; age range 5-10 y, mean age 7 y 4 mo [SD 2 y]); and (3) 13 comparison children with normal motor function (seven males, six females; age range 4-11 y, mean age 7 y 2 mo, [SD 2 y]). The children with CP were classified according to the Gross Motor Function Classification System: eight were Level I, five were Level II, four were Level III, and one was Level IV. Surface electromyography was recorded from four proximal and distal lower extremity (LE) muscles. Children with CP more frequently activated a muscle other than the intended prime mover first, compared with the comparison children, especially when the prime mover was a distal muscle. For example, during ankle plantar flexion, when the lateral gastrocnemius muscle was the prime mover, children with hemiplegia showed preactivation of the tibialis anterior muscle and children with diplegia showed medial hamstring coactivation. In conclusion, children with CP showed considerable differences to the comparison children in how LE muscles were voluntarily activated. Greater understanding of muscle recruitment patterns under a variety of tasks may provide new directions for motor control retraining or other forms of intervention.

Cerebral Palsy↗

PubMed1995

Preparatory postural adjustments in parkinsonian patients with postural instability.

BACKGROUND: Postural instability is a common problem in patients with Parkinson's disease. This paper reports results of a study undertaken to investigate some of the possible mechanisms responsible for this instability. METHODS: Preparatory postural adjustments associated with a lateral leg raising task were studied in five parkinsonian patients and four age-matched controls. Recordings included ground reaction forces, kinematics, and surface EMG activity from multiple leg muscles. RESULTS: In normal subjects there was a well-defined sequence of events preceding the onset of leg elevation, beginning with a transfer of centre of foot pressure (CP), initially toward the moving leg and then back to the support side, followed by displacement of the trunk toward the support side. In the more severely affected parkinsonian patients, the amplitude of the initial displacement of CP was markedly reduced. The interval between the earliest force changes and the onset of leg elevation was prolonged and the relative timing of the kenematic adjustments during this interval was disrupted. In addition the alternating burst and periods of inhibition observed in the EMG recordings from the normal subjects were replaced by continuous tonic EMG activity. CONCLUSIONS: These observations suggest that abnormalities in programming preparatory postural adjustments may contribute to postural instability in some patients with advanced Parkinson's disease.

Aged↗

PubMed2002

Brief report: postural reactivity to fast visual motion differentiates autistic from children with Asperger syndrome.

The aim of the present study was to search for a sensorimotor marker (i.e., visuopostural tuning) that could be correlated with the severity of motor impairments in children with autistic spectrum disorders. Given that autistic children were previously reported to be posturally hyporeactive to visually perceived environmental motion in comparison with normal control children (Gepner et al., 1995), we sought to determine whether children with Asperger syndrome (AS) would share the same postural hyporeactivity to visual motion. Three autistic children with mild to severe motor impairments, three AS children with soft motor signs, and nine normal control children were tested for overall postural instability and postural reactivity to environmental motion. Results indicate, first, that overall postural instability is significantly reduced in autistic children compared with both AS and normal children. Second, although postural oscillations in the fore-aft axis become more attuned to the oscillation frequency of an immersive dynamic visual display as visual speed is increased, in both control and AS subjects, this is not the case in autistic children. Despite the small number of subjects tested in this study, our data confirm the existence of a visuopostural detuning in autistic children. Third, they argue for a correlation between visuopostural tuning and severity of motor signs in children with autistic spectrum disorders. Finally, they suggest a differentiation between children with autism and children with AS with regard to postural reactivity to fast visual motion. Neurophysiological implications of these results are discussed. In particular, a visuocerebellar pathway deficit hypothesis in autism is proposed.

Asperger Syndrome↗

PubMed2002

Effect of static and dynamic influences on receptors of equilibrium organ of Helix lucorum after 163-day orbital flight in "Mir" station.

A 163-day orbital flight increased the baseline impulse activity of statocyst receptor cells in terrestrial pulmonata snail Helix lucorum. The maximum of reaction to step static stimuli (changes in body position in the range from 0 to 180 degrees) was significantly shifted by 30 degrees from gravitational vertical, while the reaction to dynamic stimuli (dumped sinusoidal oscillations) faded more rapidly than in control animals.

Animals↗

PubMed2000

Postural disturbance in patients with normal pressure hydrocephalus.

The postural function in 52 patients with normal pressure hydrocephalus (NPH) and in 19 patients with subcortical arteriosclerotic encephalopathy (SAE) was analysed bedside and in 17 of the NPH, 10 of the SAE and 23 healthy individuals (HI) also examined with a force platform. At the bedside examination, no differences in postural functions between NPH and SAE patients were found. The NPH patients improved more in the postural than in motor functions after shunt surgery. The NPH patients had a larger sway area and a higher backward directed velocity of centre of pressure than HI. The direction of the inclination in the sagittal plane was neutral or forward in the NPH and the SAE patients while it was backward in HI. The postural function was better in positions with open eyes in all 3 groups, but significantly less in the NPH patients, indicating a misinterpretation of afferent visual stimuli in the brainstem postural centre.

Aged↗

PubMed2003

Muscle strength, disability and mortality.

The aims of this review are to address (1) the role of muscle strength in the disablement process and (2) muscle strength as a predictor of length of life using data from prospective studies. Functional limitations, such as slow walking speed, predispose older people to disabilities. How much strength is needed for daily motor tasks such as walking varies according to other impairments present. For example, when postural balance is good, only minimum amount of strength is needed for walking. However, in the presence of balance impairment, having good level of strength may help to compensate for the deficit. Having strength well above the required level indicates reserve capacity. It was studied using data from the Honolulu Heart Program launched in 1965 among 8006 men initially aged 45-68 years, whether reserve of strength would be protective of development of future disability. All men with documented diseases at baseline were excluded from the analyses. Those men who were in the lowest third of the distribution of grip strength at baseline were at two to three times greater risk of developing disabilities assessed 25 years later compared to the highest third. It is possible that before they reach the disability level, those with greater reserve of strength may afford to lose more strength, for example following bed rest and inactivity associated with an illness. Midlife grip strength was also found to predict long-term total mortality: those with poorer strength at baseline were more likely to die over the follow-up period of 30 years. The association between muscle strength and disability is largely explained by biomechanical mechanisms. However, the mechanism explaining the association between muscle strength and mortality risk still remains to be explored.

Activities of Daily Living↗

PubMed1992

How do somersaulters land on their feet?

Body movements of trampolinists landing upright from forward somersaults, with eyes open and closed, were analyzed to test a theory of how braking and timing of actions are conjointly controlled. In regulating landing, rotation has to be slowed by extending the body so that it reaches the upright just as the feet hit the trampoline. Extending a theory of visual control of linear braking, it was hypothesized that upright landing is achieved by perceptually regulating body extension so as to keep the ratio angle of body to upright: rate of change of angle (the tau function of the angle) proportional to time-to-landing. The data support the hypothesis, indicate that vision improves precision of control, and argue further for the value of the tau function in the perceptual regulation of action.

Attention↗

PubMed1996

Visual control of posture during walking: functional specificity.

Three experiments examined the functional specificity of visually controlled posture during locomotion by presenting large-screen displays to participants walking on a treadmill. Displays simulated locomotion down a stationary hallway, a hallway that traveled with the observer, or a frontal wall that traveled with the observer. A superimposed oscillation specified postural sway in 6 possible directions. With the wall, sway amplitude was isotropic and directionally specific in all conditions. However, with the hallways, sway was anisotropic (lateral > anterior-posterior [AP]), and diagonal responses were flattened into the lateral plane. When the treadmill was turned 90 degrees to the hallway, both the anisotropy and flattening were reversed (AP > lateral), indicating that they are determined by the visual structure of the scene. The results can be explained by postural control laws based on both optical expansion and motion parallax, yielding biases in planar environments that truncate parallax.

Adult↗

PubMed1987

Intratympanic injection of sodium arsanilate (atoxyl) solution results in postural changes consistent with changes described for labyrinthectomized rats.

Intratympanic injections of sodium arsanilate (atoxyl) have been shown to produce vestibular dysfunction in the rat. Unilateral and bilateral dysfunction can be distinguished by changes in the animals' postures. These changes are consistent with changes described for unilateral or bilateral labyrinthectomized rats. The intratympanic injection technique offers a simple yet effective alternative to labyrinthectomy.

Animals↗

PubMed1996

HemiParkinson analogue rats display active support in good limbs versus passive support in bad limbs on a skilled reaching task of variable height.

Rats with unilateral dopamine (DA) depletion (hemiParkinson analogue rats) are impaired in using the contralateral (bad) limbs for skilled movements and for postural adjustments and compensate by using their good limbs in novel ways. The present study consisted of a reaching task in which compensatory adjustments using the good limbs would not be affective, thus forcing the rats to use their bad limbs. The DA-depleted rats failed to use their bad hindlimb to extend their reach at high reaching heights and failed to lower their body with their bad forelimb to reach at low reaching heights. It is suggested that extensive DA depletion may result in the loss of the ability to apply forces with the affected limbs.

Animals↗

PubMed1993

Postural effects on manual reaching laterality in squirrel monkeys (Saimiri sciureus) and cotton-top tamarins (Saguinus oedipus).

Squirrel monkeys (Saimiri sciureus) and cotton-top tamarins (Saguinus oedipus) made unimanual food reaches from either a horizontal, quadrupedal posture or a vertical, clinging posture. No population-level handedness occurred in either species. However, in both species, directional lateral preferences weakly expressed for reaching from the stable quadrupedal posture were intensified in the vertical cling posture. This phenomenon, which we designate as soft handedness, may have been an evolutionary precursor to population-level handedness. Right or left turning by the squirrel monkeys before reaching closely predicted use of the right or left hand. However, the magnitude of the association decreased in the more highly lateralized vertical cling condition. This result suggests that as lateral hand preference increases, hand use may become increasingly independent of constraints from prior behavioral and environmental influences.

Animals↗

PubMed1995

Effect of posture on hand preferences during experimental food reaching in bonobos (Pan paniscus).

The effect of posture on hand preferences was examined in an experiment with 5 bonobos (Pan paniscus). To obtain a food reward, the animals had to adopt 1 out of 7 different postures. These postures represented an increasing problem to the maintenance of body equilibrium. It was expected that an increasing demand for equilibrium maintenance would elicit individual preferences and a population-level bias. All animals showed an increasing trend toward left-handedness while shifting to a bipedal posture from a seated posture by way of a quadrupedal posture. The importance of bipedalism in the evolution of left- and right-handedness is discussed briefly.

Animals↗

PubMed1984

Development and evaluation of a universal contoured cushion.

A new wheelchair seat cushion has been developed which reduces the ischaemia producing forces and redistributes them to the more tolerant areas of the posterior thighs and lateral gluteal muscles. The cushion is fabricated of foam materials and designed to stabilise the pelvis and promote proper spinal-pelvic alignment. Pressure measurements were recorded at the skin cushion interface for 66 subjects while seated on the cushion in their own wheelchair. The cushion was considered effective if maximum interface pressures recorded were: coccyx: less than 20 mmHg, ischii: less than 65 mmHg, trochanters: less than 70 mmHg, and posterior thighs: less than 80 mmHg. The cushion was considered ineffective if the interface pressure at any one location exceeded these criteria. The cushion was found effective for 52 of the subjects. The cushion was more effective (90 per cent versus 58 per cent) for subjects without certain skeletal deformities (pelvic obliquity, bony resections). Eighty-three per cent of the respondents who were followed on the cushion reported that they preferred the cushion to their previous cushions with improved posture, balance and comfort being the most commonly cited reasons. This study has shown the cushion to be a preferred alternative to other commercially available wheelchair cushions for those who are paraplegic.

Adult↗

PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗

PubMed2002

Static stabilometry in patients with migraine and tension-type headache during a headache-free period.

The vestibulospinal system was evaluated using a stabilometric method in patients with migraine and episodic tension-type headache during headache-free periods. Migraine patients often complain of dizziness or vertigo during headache attacks and some exhibit these symptoms between attacks. Computerized static stabilometry is a reliable and non-invasive technique to evaluate the equilibrium function in various diseases. The subjects consisted of 21 patients with migraine, 12 patients with episodic tension-type headache and, age- and sex-matched controls. We performed two sets of static stabilometric measurements with eyes open (EO) and eyes closed (EC) for 30 s. The averages of two sessions of the following six stabilometric parameters were used for the analysis: locus length (LNG), environmental area (ENV-AREA), rectangle area (REC-AREA), locus length per second, locus length per environ area (L/E), and root mean square area. Romberg quotients (EC/EO) of these six parameters were also analyzed. The mean values of LNG, ENV-AREA and REC-AREA in the EC session in the migraine group were significantly greater than those in the controls (P < 0.05, Mann-Whitney rank sum test). Romberg quotients of all stabilometric parameters except the L/E in the migraine group were significantly greater than in the controls. Patients with episodic tension-type headache did not show any differences in the stabilometric study from the controls. The present findings suggest that patients with migraine show a significant increase of the body sway during the EC session, which indicates an underlying dysfunction in the vestibulospinal system.

Adolescent↗

PubMed1999

Different postural reaction patterns for expected and unexpected perturbations in patients with idiopathic Parkinson's disease and other parkinsonian syndromes.

Different postural reaction patterns after predictable and unpredictable perturbations during free stance were studied in 8 patients with idiopathic Parkinson's disease (iPD), in 4 patients with other parkinsonian syndromes (PS) and in 5 healthy controls. First, the amplitude of leaning maximally backward and forward was measured (condition I). Secondly, the body equilibrium was disturbed by self-paced, predictable, rapid arm elevations (condition II) and by sudden unpredictable toe-down and toe-up rotations of a supporting platform (condition III). Patients with PS particularly had difficulties in regaining body equilibrium after unexpected perturbations. In controls and patients with PS, unpredictable disturbances were better compensated in toe-down than in toe-up direction, whereas the opposite was true for patients with iPD. These results correspond to the fact that patients with PS had a specific leaning-backward impairment and patients with iPD, a leaning-forward impairment. The authors conclude that the differences in postural stability between patients with iPD and PS are caused by different pathophysiological mechanisms. These differences in postural stability could serve as an additional tool for differential diagnosis.

Aged↗

PubMed2002

The effect of refractive blur on postural stability.

The effect of refractive blur upon postural stability was investigated under three conditions: normal standing, standing with input from the somatosensory system disrupted and standing with input from the somatosensory and vestibular systems disrupted. Standing stability was assessed using the centre of pressure (COP) signal from force plate data in four young subjects (mean 23.9+/-3.1 years) and five repeated sets of measurements were taken. The subjects looked straight ahead at a horizontal and vertical square wave pattern of 2.5 cycles (degree)(-1). Under each of the three test conditions, standing stability was measured with the optimal refractive correction and under binocular blur levels of 0, + 1, + 2, + 4, and + 8 D and with eyes closed. In the normal standing condition, dioptric blur had only a mild effect on postural stability. However refractive blur produced large increases in postural instability when input from one or both of the other two sensory systems were disrupted. We hypothesized that dioptric blur would have an even great effect on postural stability if the visual target used was of higher spatial frequency. This was confirmed by repeated measurements on one subject using a target of 8 cycles (degree)(-1). The study highlights the possible importance of an optimal correction to postural stability, particular in situations (or people) where input from the somatosensory and/or vestibular systems are disrupted, and where the visual surrounds are of high spatial frequency.

Adult↗

PubMed2001

Tai Chi Chuan practice as a tool for rehabilitation of severe head trauma: 3 case reports.

Rehabilitation after severe head trauma is a complex process that can be long and frustrating. New, more holistic methods for rehabilitation are constantly sought. We present the cases of 3 patients who had severe head injury and whose rehabilitation was facilitated by Tai Chi Chuan (TCC) therapy. TCC therapy should be taught only by a qualified TCC therapist and under close medical supervision.

Accidental Falls↗