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At least 1,477 records · Page 82Linked to original sources
PubMed1999

[Effects of motion sickness evoked by parallel swing stimulation on posture equilibrium].

Objective. To study the effects of motion sickness on posture equilibrium. Method. Dynamic posture was tested pre- and following motion sickness evoked by parallel swing. 17 healthy men were divided into motion sickness sensitive group (12) and motion sickness insensitive groups (5) according to their endurance times and the severeness of symptom. Result. The composite equilibrium score significantly decreased post-swing in all subjects. The composite equilibrium score, certain other equilibrium scores (SOT4, SOT5 and SOT6), the strategy scores (STRAT4 and STRAT6) and the sensory score (SEN3 and SEN5) significantly decreased in the sensitive group, but unchanged in the insensitive group post-swing. The equilibrium score (SOT2), and the sensory score (SEN1) pre-swing, the strategy score (STRAT3) of insensitive group is significantly higher than the sensitive group. Conclusion. Motion sickness can influence postural equilibrium. Postural instability and instability of strategy are related to the sensitiveness to motion sickness.

Adolescent↗
PubMed1976

Characteristics of postural self-regulation in complex spatial environments and after-effects of weightlessness.

The structure of the postural-spatial activity of parachuters, high-board divers and volunteers has been studied during postural tests on sports towers and that of cosmonauts before and after space flight. The experimental results give evidence that the stabilographic pattern shows several different types which correspond to the fixed, "searching" and pliable models of postural self-regulation, regardless of professional experience. During postural tests the cosmonauts exhibited deformation of the stabilographic pattern which lost its individual features and was converted into a stable curve which was represented by unmodulated fluctuations with a period of 0.15 sec that was similar to the fixed model. Psycho-physiological mechanisms of the changes are discussed.

Adaptation, Physiological↗
PubMed1991

[Imbalance of the postural system studied by light stimulation in children with strabismus].

The postural displacements on a statokinesimetric plateform of squint-eyed children during short monocular lighted stimulations show that their postural regulation is different from that of normal children of the same age. The provoked amplification of the displacements is larger, their direction is no more systematized but once adopted it remain stable. The orthoptic treatment associated with prismus lenses and postural reeducation often allows to double their postural performances.

Adolescent↗
PubMedDate not supplied

[Physiological characteristics of posture maintenance by dogs during immediate reaction to irradiation].

The ability of dogs to maintain a vertical posture during the first hours after irradiation at a dose of 10 or 80 Gy was investigated. Two experiments were performed. In the first experiment, during 5 hours after irradiation the vector stabilogram area, peak muscle efforts and sensorimotor coordination were measured 10 times every 30 min. In the second experiment, postural responses to perturbations were measured before and after irradiation at a dose of 10 Gy. During exposure to 10 Gy maximum values of the vector stabilogram area reflected initial excitation and motor unrest, that preceded vomiting, while minimum values of the parameter were related to hypodynamia during 3-5 hours after exposure. During exposure to 80 Gy minimum values of the vector stabilogram area reflected the hypodynamic phase while maximum values were related to the phase of distinct cerebral lesions. A reliable indicator of the quality of vertical posture maintenance, that correlates with the post-irradiation quality of purposeful actions, including intermittent physical acts, or actions, requiring highly precise coordination, is the rate of posture recovery after instantaneous platform displacement. This parameter declined after irradiation, the maximum decrease being during the 4-5th hour.

Animals↗
PubMed1990

Extraneous movement associated with hemiplegic postural sway during dynamic goal-directed weight redistribution.

The locus of postural stability during dynamic, visually cued weight redistribution was studied in six hemiplegic and five able-bodied subjects. After a verbal warning with a variable foreperiod, a visual trace appeared on an oscilloscope to indicate a sway magnitude equaling half the subject's maximal voluntary sway. Body movement was cued in three directions--forward, and toward the paretic and nonparetic lower extremities. In order to assess extraneous postural patterns, all three directions of sway were analyzed for each trial. The results showed that with cued lateral sway (right or left) there was a tendency for hemiplegic subjects to reduce the dispersion (or variability) of the sway path. Clustering of the active lateral postural response near the geometric center of the sway path indicated a restricted balance response in this plane of motion. During cued forward sway the variability of the sway path was not statistically different from the able-bodied, but three-dimensional visualization of the sway pattern illustrated a qualitatively different postural response with extraneous, nonfocused balance activity biased toward the nonparetic lower extremity. Short-term practice did not alter the dispersion of the sway path for hemiplegic or able-bodied subjects in any direction. Hemiplegic extraneous movement in one case (forward sway) and restricted movement in another (lateral sway) emphasize the level of specificity which needs to be addressed during rehabilitation of balance.

Adult↗
PubMed1990

[Correlation of the evoked vestibulo-postural reaction and spontaneous body sway while standing].

The stability of upright posture was studied by the method of stabilometry in 16 healthy subjects. The efficacy of involving visual, vestibular and proprioceptive afferentation in maintaining posture was examined in four test situations. A direct correlation of stabilometric parameters was established at posture on soft surface and at galvanic stimulation of the vestibular analyzer. The recorded data indicate an indirect correlation between the sensitivity of the vestibular sensor and the sensitivity of that part of the central nervous system which processes vestibular information. The observed relationship results presumably from the action of central compensatory mechanisms in the function of the vestibulo-postural circuit.

Adult↗
PubMed1990

[Physiologic range of stabilometry values obtained in the upright posture using a computer].

The authors present physiological ranges of values of seven parameters of stabilometric examinations of the upright posture in man. In order to make the examination effective, the authors suggested and tested three situations which make it possible to characterize the activity of the visual, vestibular and proprioceptive feedback in the process of maintenance of the upright posture. For measuring the supporting forces during the upright posture the authors used a stabilometer with automatic compensation of the body weight. Amplitude analysis of the obtained stabilometric curves was made "on line" by means of a microcomputer PMD 85-2. The mentioned stabilometric parameters make it possible to evaluate objectively the ability of the subject to maintain an upright posture based on a) the median amplitude and velocity of deviations of the body in an anterioposterior and lateral direction, b) complex parameters of the length of the curve, the total area and root mean square deviation of the statokinezigram.

Adult↗
PubMed1988

Postural sway biofeedback: its effect on reestablishing stance stability in hemiplegic patients.

A static force plate system was used to examine postural sway characteristics in 16 hemiplegic patients and in 34 normal elderly subjects. The effectiveness of postural sway (center of pressure) biofeedback was compared to conventional physical therapy practices in reestablishing stance stability in hemiplegic patients. Postural sway abnormalities in hemiplegic patients included significant mean lateral displacement of sway towards the nonaffected leg and increased total sway area. Postural sway biofeedback was more effective than conventional physical therapy practices in reducing mean lateral displacement of sway. This was associated with increased loading of the affected leg. Posttreatment changes in total sway area were not significantly different between experimental and control groups.

Aged↗
PubMed1985

Changes of posture during transient perturbations in microgravity.

The control of goal-directed arm movement and of body stability before, during, and 3 d after a 7-d spaceflight has been investigated. The findings show that the anticipatory and compensatory activities of the postural muscles were highly reproducible during the first days of the space mission. The sequence of these activities, studied in two situations--in which the platform either was fixed or could rotate about near the rotation axis of the ankle--was similar to a ground-based situation. The trajectory of various body segments demonstrates that a 7-d exposure to microgravity did not result in major changes in posture. Furthermore, vision seemed to play an important role in the control of standing posture at the beginning of the flight. Postural perturbations, elicited by unexpected displacements of the foot support, involved leg muscle reflexes whose amplitudes were greatly reduced compared to those on earth.

Ankle Joint↗
PubMed1994

Postural stability, falls and fractures in the elderly: results from the Dubbo Osteoporosis Epidemiology Study.

OBJECTIVE: To assess measures of postural stability in a large population of persons aged over 60 years in order to compare performance between fallers and non-fallers and relate postural stability to fracture prevalence. METHODS: The sensorimotor, visual and balance functions were measured in 1762 ambulatory, community-dwelling patients aged between 60 and 100 years (mean age, 70.1 years) living in a large semi-urban Australian city. A history of recent falls and fractures was recorded at the time of assessment. RESULTS: The prevalence of impairment in all tests increased with age. Men performed significantly better than women in tests of muscle strength, visual field dependence, sway on the floor with eyes open and dynamic balance. In the 12 months before testing, 72.3% of the patients experienced no falls, 18.4% fell only once and 9.3% fell on two or more occasions. Multiple fallers had weaker quadriceps, poorer tactile sensitivity, greater visual field dependence and greater body sway than other patients. Test scores for once-only fallers were mostly between those for non-fallers and multiple fallers. Those who suffered recent fall-related fractures had significantly reduced tactile sensitivity and quadriceps strength and increased body sway. Postural stability was also impaired in patients taking psychoactive and/or anti-hypertensive medications. CONCLUSION: Tests of postural stability can identify, independently of age, individuals living in the community who are at risk of falls and fall-related fractures.

Accidental Falls↗
PubMed1996

Disorders of posture, balance, and gait in Parkinson's disease.

Disorders of movement function related to posture, balance, and gait are common occurrences for many persons with Parkinson's disease. Numerous studies have identified a broad variety and heterogeneous distribution of postural and locomotor changes. These alterations are often associated with diminished functional ability, poor prognosis, and frequent falls. Present pharmacologic management appears to have a limited influence on postural instability and associated falls, and, despite anecdotal information, there is scant information on the therapeutic effectiveness of physical interventions aimed at enhancing these functions. Future advances would likely be facilitated by: (1) determining the nature and extent of the specific involvement of postural and locomotor control mechanisms; (2) coalescing findings on motor control processes with clinical information to develop rehabilitation approaches that target specific motor manifestations; and (3) conducting long-term clinical trials to demonstrate the efficacy of interventions.

Accidental Falls↗
PubMedDate not supplied

[The use of prisms in postural equilibrium].

The syndrome of postural deficiency represents an alteration of tonic and postural equilibrium, related to the affectation of the reception, transmission and integration of proprioceptive and visual information. The physiological, semiological and therapeutical basis of the syndrome of postural deficiency are discussed. In order to prescribe a postural therapeutical prism, the ophthalmologist may choose among two methods with common physiological base. The former, proposed by the Paris School, tries to use the prism treatment in order to obtain a re-equilibrating hypertonia: the latter, used by the Lisbon School, tries to create initially an equilibrating relaxation and, since it is much easier to use during the ophthalmological consultation and faster is preferred by most authors.

Eyeglasses↗
PubMed1994

Control of posture in patients with neurologically asymptomatic HIV infection and patients with beginning HIV-1-related encephalopathy.

OBJECTIVE: Stance control measurements (sway velocity, sway area, and postural reflexes) were performed in 36 patients with neurologically asymptomatic human immunodeficiency virus infection (HIV) and in 10 patients with beginning HIV type 1 (HIV-1)-related encephalopathy. All recordings were performed using a movable platform system. OBSERVATIONS: Static posturography and postural reflexes revealed pathologic results in patients with beginning HIV-1-related encephalopathy and in about 25% of patients with nonsymptomatic HIV infection in comparison with age- and sex-matched control subjects. CONCLUSIONS: Postural control is well preserved in early HIV infection; thus, it is not an appropriate measure for detecting subclinical deficits, but disturbances of postural control seem to be one of the first neurological abnormalities in patients with beginning HIV-1-related encephalopathy.

AIDS Dementia Complex↗
PubMed1999

Kinematic data on primate head and neck posture: implications for the evolution of basicranial flexion and an evaluation of registration planes used in paleoanthropology.

Kinematic data on primate head and neck posture were collected by filming 29 primate species during locomotion. These were used to test whether head and neck posture are significant influences on basicranial flexion and whether the Frankfurt plane can legitimately be employed in paleoanthropological studies. Three kinematic measurements were recorded as angles relative to the gravity vector, the inclination of the orbital plane, the inclination of the neck, and the inclination of the Frankfurt plane. A fourth kinematic measurement was calculated as the angle between the neck and the orbital plane (the head-neck angle [HNA]). The functional relationships of basicranial flexion were examined by calculating the correlations and partial correlations between HNA and craniometric measurements representing basicranial flexion, orbital kyphosis, and relative brain size (Ross and Ravosa [1993] Am. J. Phys. Anthropol. 91:305-324). Significant partial correlations were observed between relative brain size and basicranial flexion and between HNA and orbital kyphosis. This indicates that brain size, rather than head and neck posture, is the primary influence on flexion, while the degree of orbital kyphosis may act to reorient the visual field in response to variation in head and neck posture. Regarding registration planes, the Frankfurt plane was found to be horizontal in humans but inclined in all nonhuman primates. In contrast, nearly all primates (including humans) oriented their orbits such that they faced anteriorly and slightly inferiorly. These results suggest that for certain functional craniometric studies, the orbital plane may be a more suitable registration plane than Frankfurt "Horizontal."

Animals↗
PubMed1998

Effects of upright posture on hand preference for reaching vs. the use of probing tools by tufted capuchins (Cebus apella).

This research examined the effects of task (reaching vs. tool use) and posture (quadrupedal vs. bipedal) on hand preference in tufted capuchins (Cebus apella). Regarding direction of hand preference, we found a significant main effect of posture, as the bipedal stance elicited greater use of the right hand than did the quadrupedal stance, and a significant posture x task interaction, as bipedal reaching elicited greater use of the right hand than did other postural and task conditions. Further, we found a significant main effect of task on strength of hand preference, as tool use elicited more consistent use of one hand over the other than did reaching. Our findings indicate that bipedal reaching facilitates a mild right-hand bias in intensely manipulative primates. We speculate that this moderate bias may have been pushed in the direction of nearly exclusive right-hand preference in most humans with the development of complex tool use.

Animals↗
PubMed2001

Ontogeny of locomotion in rhesus macaques (Macaca mulatta): II. Postural and locomotor behavior and habitat use in a free-ranging colony.

This study quantifies changes in postural and locomotor behavior as well as habitat use across the life span of free-ranging rhesus macaques (Macaca mulatta) in the Cayo Santiago colony in Puerto Rico. It focuses on developmentally related changes from birth to adulthood, and complements an earlier study by Turnquist and Wells ([1994] J Hum Evol 26:487-499) on the early postnatal ontogeny of the musculoskeletal system of the same colony. A total of 6,551 locomotor and postural events was analyzed. Selection and use of substrate correlated well with age. The more sedentary adult and dependent infant select safe, wide, horizontal arboreal settings in contrast to the older Infant IIs and Juveniles, who are learning locomotor and postural skills through independent chase and play. Infant macaques, when independent, often employ a low center of gravity and widely abducted limbs in order to broaden their contact with the base of support. This study shows that the previously reported ontogenetic changes in morphology are closely paralleled by changes in postural and locomotor behavior, and these in turn are correlated to changes in habitat use, particularly during the formative years.

Adaptation, Physiological↗
PubMed2003

Nonlinear analysis of the development of sitting postural control.

The development of sitting postural control in five normal infants was examined longitudinally at three stages of sitting: Stage 1, when infants could hold up their head and upper trunk, but could not sit independently; Stage 2, when infants began to sit independently briefly; and Stage 3, when infants could sit independently. Methods from nonlinear dynamics were used to analyze center of pressure (COP) data during sitting in terms of stability of the neuromuscular system (Lyapunov Exponent), movement dimensionality (Correlation Dimension), and complexity/regularity (Approximate Entropy). Results indicated significant changes in the nonlinear measures over time, with increased stability and increased regularity revealing a more stable and periodic strategy of maintaining postural control. Dimensionality decreased from Stage 1 to 2, indicating a constraint of the degrees of freedom. Subsequently, dimensionality increased from Stage 2 to 3, indicating a release of the degrees of freedom as sitting independence emerged. Nonlinear analysis of the COP time series supports the perspective that the development of postural control is a dynamic process whereby the infant learns to control the body's degrees of freedom to achieve the sitting posture.

Child Development↗
PubMed2001

New vascular system in reptiles: anatomy and postural hemodynamics of the vertebral venous plexus in snakes.

Using corrosion casting, we demonstrate and describe a new vascular system--the vertebral venous plexus--in eight snake species representing three families. The plexus consists of a network of spinal veins coursing within and around the vertebral column and was previously documented only in mammals. The spinal veins of snakes originate anteriorly from the posterior cerebral veins and form a lozenge-shaped plexus that extends to the tip of the tail. Numerous anastomoses connect the plexus with the caval and portal veins along the length of the vertebral column. We also reveal a posture-induced differential flow between the plexus and the jugular veins in two snake species with arboreal proclivities. When these snakes are horizontal, the jugulars are observed fluoroscopically to be the primary route for cephalic drainage and the plexus is inactive. However, head-up tilting induces partial jugular collapse and shunting of cephalic efflux into the plexus. This postural discrepancy is caused by structural differences in the two venous systems. The compliant jugular veins are incapable of sustaining the negative intraluminal pressures induced by upright posture. The plexus, however, with the structural support of the surrounding bone, remains patent and provides a low-pressure route for venous return. Interactions with the cerebrospinal fluid both allow and enhance the role of the plexus, driving perfusion and compensating for a posture-induced drop in arterial pressure. The vertebral venous plexus is thus an important and overlooked element in the maintenance of cerebral blood supply in climbing snakes and other upright animals.

Animals↗