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Results for “Postural control”

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At least 379 records · Page 21Linked to original sources

PubMed2003

The effect of a simulated knee joint effusion on postural control in healthy subjects.

OBJECTIVE: To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing. DESIGN: Quasi-experimental design. SETTING: Sports injury research laboratory in a university setting. PARTICIPANTS: Twenty healthy volunteers, 10 of whom (age, 20.1+/-2.4y; height, 168.0+/-8.1cm; weight, 70.4+/-13.3kg) were assigned to an effusion group and 10 of whom (age, 25+/-3.8y; height, 169.4+/-8.9cm; weight, 74.7+/-7.7kg) were assigned to a control group. INTERVENTIONS: COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space. MAIN OUTCOME MEASURES: COP path and mediolateral and anteroposterior MPF. RESULTS: COP path decreased after the effusion (pre-effusion mean, 92.2+/-21.9cm; posteffusion mean, 77.27+/-23.0cm). No change was found within the control group for COP path (P>.05). No differences were detected before or after joint effusion when the MPF was examined (P>.05). CONCLUSIONS: Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension.

Adult↗

PubMed2000

Scaling-violation phenomena and fractality in the human posture control systems.

By analyzing the movements of quiet standing persons by means of wavelet statistics, we observe multiple scaling regions in the underlying body dynamics. The use of the wavelet-variance function opens the possibility to relate scaling violations to different modes of posture control. We show that scaling behavior becomes close to perfect, when correctional movements are dominated by the vestibular system.

Fourier Analysis↗

PubMedDate not supplied

Postural control in order to prevent chronic locomotor injuries in top level athletes.

Chronic injuries of the locomotor apparatus represent the main cause of drop-out among top level gymnasts. The aim of the present paper was to verify whether the postural control, investigated by using an integrated approach and accordingly optimized, could be an effective tool for the secondary prevention of training-related disorders of the locomotor apparatus, in a cohort of 20 young female athletes practicing rythmic gymnastic at top level. After a preliminary medical consultation all the subjects underwent a static and dynamic baropodometric test, an ophtalmological and a dental screening. Then athletes were given prescriptions based upon the results of the above named examination. After 6 months, symptoms were completely disappeared in 80% and remarkably improved in 20%, and at baropodometric test, the contact duration as well as the contact surface, the max and mean contact pressure were significantly increased in all the athletes. Our data show that the proposed integrated approach is actually an effective tool for the secondary prevention of training related disorders of the locomotor apparatus.

Adolescent↗

PubMedDate not supplied

Postural control responses sitting on unstable board during visual stimulation.

Concerning with the relation of vection induced by the optokinetic stimulation and the body movement, especially we attended to the neck joint movement, which counteracted to the shoulder movement. Then, we analyzed the mechanisms of the sitting postural control by using the seesaw board. By the optokinetic stimulation through the head mounted display (H.M.D.), the vection was leaded, and it affected to the sway of the body on the seesaw board. In this experiment, we found that the movement of upper part of body except for the head was the same direction to the seesaw board but the head moved out of phase to the seesaw board. This phenomenon will be suggested that the unstable condition of sway is balanced by the counter swing of head and the neck muscle tonus is controlled by acting of the vestibulo-collic reflex.

Adult↗

PubMed2001

Postural control in the elderly: an analysis of test-retest and interrater reliability of the COP-COM variable.

OBJECTIVES: To estimate the test-retest and interrater reliability of the center of pressure-center of mass (COP-COM) variable of postural control in the elderly. DESIGN: The biomechanic variable COP-COM, which represents the distance between the COP and the COM, was determined from 2 AMTI force platforms and 3 OPTOTRAK position sensors. Measurements were taken in quiet position, double leg stance, and eyes open and eyes closed conditions. SETTING: Laboratory environment. PARTICIPANTS: Forty-five healthy subjects, 8 patients with diabetes neuropathy, and 7 stroke survivors, all of whom were at least 60 years old. INTERVENTIONS: Subjects were evaluated on 2 separate occasions within 7 days by the same evaluator to determine test-retest reliability. Interrater reliability was determined the same day. MAIN OUTCOME MEASURES: The biomechanic variable COP-COM, which represents the distance between the COP and the COM in terms of root mean square. The mean of 4 trials of the COP-COM variable for each condition was used for statistical analysis. Intraclass correlation coefficients (ICCs) were used. RESULTS: The COP-COM variable has good reliability for both the test-retest and interrater studies, but its reliability varies according to the direction of the COP-COM. For the test-retest and interrater studies, the ICC ranged from.89 to.93 in the anteroposterior direction and from.74 to.79 in the mediolateral direction. CONCLUSION: The equivalence of the test-retest and interrater coefficients obtained suggests that the measurement error of the COP-COM variable is mainly linked to the biologic variability of this measure over a short period of time. Using the mean of 4 trials stabilizes the COP-COM variable enough to be potentially used to evaluate clinical change.

Accidental Falls↗

PubMedDate not supplied

A content analysis of physiotherapy for postural control in people with stroke: an observational study.

PURPOSE: The lack of information about the content of therapy packages is a frequent criticism in stroke rehabilitation research. This study aimed to describe, in detail, the content of one aspect of physiotherapy; the rehabilitation of postural control. METHODS: The design was a cross-sectional survey and the setting was in 11 NHS Trusts. The participants were 35 stroke physiotherapists working in acute and rehabilitation settings who recorded the treatment of 132 patients in 644 treatment sessions using the Stroke Physiotherapy Intervention Recording Tool. Analysis was carried out by descriptive statistics, one-way ANOVAS and chi-squares which were used to describe content of interventions and effects of the aim of treatment. RESULTS AND CONCLUSIONS: Physiotherapists' clinical practice focused on therapist-led interventions, which aimed to normalize muscle tone and promote normal movement patterns. The most frequent interventions were 'preparation for treatment' (n = 1969, 43%), 'practising balance and walking activities' (n = 1583, 34%) and 'practising functional tasks' (n = 703, 15%). Interventions to encourage independence or activity outside the treatment session were rarely used. This pattern was seen regardless of the aim of treatment (the restoration of sitting balance, standing balance or stepping/walking).

Adult↗

PubMed2003

Developmental study of early posture control in preterm and fullterm infants.

In a prospective study, 10 infants born between 32 to 36 weeks of gestation and 10 infants born at fullterm were observed on day 15, and in months 1, 2 and 3. The investigation showed that the development of early postural control takes place in a sequential way in preterm infants, similar to that of in fullterm infants. However, some movement components for the acquisition of motor abilities showed a different trend in the development of preterm infants when compared to fullterm infants: the onset for the acquisition of the extensor and flexor patterns was slower and the distribution of the load bearing was less mature.

Child Development↗

PubMed2002

Facilitating postural control: effects on the reaching behavior of 6-month-old infants.

In this study, 3-D kinematic as well as 2-D videorecordings were made of the reaching behavior of infants aged about 6 months who were not yet able to sit. Detailed analyses of these recordings were directed toward specifying the effects of providing additional postural support to the lower body on the spatial and temporal features of such behavior. To detect these effects, reaching and associated head movements in this modified condition were compared to those made while the infants sat in an age-appropriate and commercially available chair lacking the supplementation of support for the pelvic region and upper legs. Findings consistent with predictions included better head stabilization and smoother reaching movements when the infants were in the modified chair. In addition, these two achievements were negatively related to reaching experience. These, and other findings, underscore the infrequently investigated supposition that changes in postural control induce improvements in the control of reaching movements during infancy. Recommendations are made about how the procedure adopted in the present study could be used in subsequent research to give further insights into the codevelopment of posture and action.

Biomechanical Phenomena↗

PubMed1998

Postural control systems in developmental perspective.

How can the adult postural organisation be elucidated using an ontogenetic approach, and what questions can be raised about ontogenesis starting from the organisation of adult posture? These questions will be addressed taking three aspects of postural organisation. The first is the internal representation of erect posture, including the role played by the various sensory inputs in this representation. The second aspect relates to the variables which are controlled during erect posture: is it the body orientation with respect to the vertical or the localisation of the centre of gravity with respect to the feet which is controlled? The third aspect concerns the coordination between posture, equilibrium and movement, focusing on the role played by an internal representation of the external world and its interactions with the body segments in organising the anticipatory postural adjustments. The central organisation of coordinated control will also be considered. Each of these aspects will be discussed in relation to ontogenetic considerations.

Humans↗

PubMed1999

Studies on spatial orientation and posture control and changes in otolith function due to linear acceleration loading.

Otolith function is directly affected by weightlessness at the time of movement in outer space, and changes occur in the mode of response. It has been known for some time that such changes occur in the posture and gait of astronauts just after they return from a trip into space. It is thought that the cause of these changes is disuse atrophy of the antigravity muscles. However, in the present study, experimental subjects underwent repeated linear acceleration loading over a long period of time, and instability of the head and a decrease in posture control, especially in relation to the gait, were observed for the first time. To date, it has been said that the otolith function has a close relationship with ocular counter rolling. However, when the otolith organ was stimulated, the response was seen to be head instability and an irregular effect on the gait. It is surmised that these findings will facilitate future research into the otolith function under gravity-free conditions.

Acceleration↗

PubMed1985

Dynamics of postural control in the child with Down syndrome.

We examined the development of neural control processes underlying stance balance in both developmentally normal children and children with Down syndrome to test the hypothesis that motor deficiencies in children with Down syndrome are associated with deficits within the automatic postural control system. We compared children with Down syndrome and developmentally normal children in two age groups (1-3 and 4-6 years) by using displacements of a platform and measuring electromyograms from leg muscles. The automatic muscle response pattern in both normal children and children with Down syndrome were directionally specific, although the pattern were more variable than in adults. Responses in children with Down syndrome showed no adaptive attenuation to changing task conditions. Onset latencies of responses in children with Down syndrome were significantly slower than in normal children. Presence of the monosynaptic reflex during platform perturbations at normal latencies suggests that balance problems in children with Down syndrome do not result from hypotonia, which researchers have defined as decreased segmental motoneuron pool excitability and pathology of stretch reflex mechanisms, but rather result from defects within higher level postural mechanisms.

Biomechanical Phenomena↗

PubMed2001

Motor preparation in postural control in seated spinal cord injured people.

Spinal cord injured (SCI) people try to compensate for the loss of postural muscle function by increased use of non-postural muscles. Such alternative muscle use, however, may necessitate important modifications in motor control. In this study motor programming processes were investigated in three groups, i.e. in high thoracic SCI, low thoracic SCI and non-SCI subjects. A bimanual forward-reaching task, in which graded sitting balance perturbation was systematically invoked, was presented to the subjects as a visual precue choice reaction time (RT) task. Effects of movement preparation were examined by precuing reaching distance information. RT and movement times were recorded. Centre of pressure (CP) displacement was used as an indicator for sitting balance perturbation. Results indicated that high thoracic SCI subjects programmed balance-perturbing reaching movements as fast as did non-SCI subjects. Low thoracic SCI subjects, on the other hand, showed substantially longer programming times. This latter outcome is consistent with the hypothesis that the low thoracic SCI subjects adopted a more complex postural control strategy involving residual motor functions in an attempt to actively compensate for loss of postural muscle function. High thoracic SCI subjects, on the other hand, appeared to adopt a less complex and thus easier to programme postural control strategy.

Adult↗

PubMed2003

Dynamic regulation of sensorimotor integration in human postural control.

Upright stance in humans is inherently unstable, requiring corrective action based on spatial-orientation information from sensory systems. One might logically predict that environments providing access to accurate orientation information from multiple sensory systems would facilitate postural stability. However, we show that, after a period in which access to accurate sensory information was reduced, the restoration of accurate information disrupted postural stability. In eyes-closed trials, proprioceptive information was altered by rotating the support surface in proportion to body sway (support surface "sway-referencing"). When the support surface returned to a level orientation, most subjects developed a transient 1-Hz body sway oscillation that differed significantly from the low-amplitude body sway typically observed during quiet stance. Additional experiments showed further enhancement of the 1-Hz oscillation when the surface transitioned from a sway-referenced to a reverse sway-referenced motion. Oscillatory behavior declined with repetition of trials, suggesting a learning effect. A simple negative feedback-control model of the postural control system predicted the occurrence of this 1-Hz oscillation in conditions where too much corrective torque is generated in proportion to body sway. Model simulations were used to distinguish between two alternative explanations for the excessive corrective torque generation. Simulation results favor an explanation based on the dynamic reweighting of sensory contributions to postural control rather than a load-compensation mechanism that scales torque in proportion to a fixed combination of sensory-orientation information.

Adaptation, Physiological↗

PubMed2006

Postural control, gait, and dopamine functions in parkinsonian movement disorders.

Balance impairments and falls, which are common in patients who have parkinsonian movement disorders, are a serious threat to the health of these individuals. However, the underlying mechanisms cannot be fully explained by presynaptic dopaminergic denervation, because balance impairment is at least responsive to L-dopa therapy. This article reviews the latest clinically relevant literature relating postural control, gait, and dopamine in patients who have parkinsonian movement disorders.

Dopamine↗

PubMed2005

Grip strength, postural control, and functional leg power in a representative cohort of British men and women: associations with physical activity, health status, and socioeconomic conditions.

BACKGROUND: Understanding the health, behavioral, and social factors that influence physical performance in midlife may provide clues to the origins of frailty in old age and the future health of elderly populations. The authors evaluated muscle strength, postural control, and chair rise performance in a large representative prospective cohort of 53-year-old British men and women in relation to functional limitations, body size, health and activity, and socioeconomic conditions. METHODS: Nurses interviewed 2984 men and women in their own homes in England, Scotland, and Wales and conducted physical examinations in 2956 of them. Objective measures were height, weight, and three physical performance tests: handgrip strength, one-legged standing balance time, and time to complete 10 chair rises. Functional limitations (difficulties walking, stair climbing, gripping, and falls), health status, physical activity, and social class were obtained using a structured questionnaire. RESULTS: Those with the worst scores on the physical performance tests had higher rates of functional limitations for both upper and lower limbs. Women had much weaker handgrip strength, somewhat poorer balance time, and only slightly poorer chair rise time compared with men. In women, health problems and low levels of physical activity contributed to poor physical performance on all three measures. In men, physical activity was the predominant influence. Heavier weight and poorer socioeconomic conditions contributed to poorer balance and chair rise times. CONCLUSIONS: In this representative middle-aged group, physical performance levels varied widely, and women were seriously disadvantaged compared with men. In general, physical performance was worse for men and women living in poorer socioeconomic conditions with greater body weight, poorer health status, and inactive lifestyles. These findings support recommendations for controlling excess body weight, effective health interventions, and the maintenance of active lifestyles during aging.

Cohort Studies↗

PubMed1986

Effect of indirect heating on the postural control of skin blood flow in the human foot.

It has been shown in previous studies that skin blood flow in the human foot falls when the extremity is placed below heart level, owing to an increase in precapillary resistance that is probably mediated by a local sympathetic axon reflex or a myogenic response. In order to clarify the influence of the central thermoregulatory mechanisms on this local postural vasoconstrictor response, 12 normal male subjects were studied under standardized conditions, at rest and during heating of the trunk with an electric blanket. Skin blood flow was measured before and during body heating using laser Doppler flowmetry with the foot maintained at heart level and placed passively 50 cm below the heart. Skin blood flow and skin temperature were determined at two sites: the plantar surface of the big toe, an area with a relatively large number of arteriovenous anastomoses, and the dorsum of the same foot, where these anastomoses are few or absent. When the foot was placed in the dependent position, skin blood flow recorded in the dorsum of the foot during indirect heating fell to a level similar to that achieved before heating. In contrast, indirect heating greatly diminished the postural fall in skin blood flow recorded in the plantar surface of the big toe. In conclusion, the partial release of sympathetic vasoconstrictor tone associated with indirect heating appears to over-ride the local postural control of cutaneous vascular tone in areas where arteriovenous anastomoses are relatively numerous.

Body Temperature Regulation↗

PubMedDate not supplied

Aminoglycoside ototoxicity in the neonatal period: possible etiologic factor delayed postural control.

Forty-three infants, treated with aminoglycosides during the neonatal period, were tested repeatedly over a period of two to five years for neurovestibular responses. Results of testing were compared with those obtained from a group of 276 healthy newborns followed simultaneously. No abnormalities were found in the untreated group. Among the treated infants, three had a sensorineural hearing loss and eight had laboratory evidence of vestibular dysfunction and delay of head and postural control.

Aminoglycosides↗

PubMed1996

Organizing sensory information for postural control in altered sensory environments.

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

Humans↗