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At least 1,333 records · Page 74Linked to original sources

PubMed2003

A model of neuro-musculo-skeletal system for human locomotion under position constraint condition.

The human locomotion was studied on the basis of the interaction of the musculo-skeletal system, the neural system and the environment. A mathematical model of human locomotion under position constraint condition was established. Besides the neural rhythm generator, the posture controller and the sensory system, the environment feedback controller and the stability controller were taken into account in the model. The environment feedback controller was proposed for two purposes, obstacle avoidance and target position control of the swing foot. The stability controller was proposed to imitate the self-balancing ability of a human body and improve the stability of the model. In the stability controller, the ankle torque was used to control the velocity of the body gravity center. A prediction control algorithm was applied to calculate the torque magnitude of the stability controller. As an example, human stairs climbing movement was simulated and the results were given. The simulation result proved that the mathematical modeling of the task was successful.

Adaptation, Physiological↗

PubMed2006

Static and dynamic standing balance: test-retest reliability and reference values in 9 to 10 year old children.

INTRODUCTION: Based on the literature, reliability reports and normative data for bilateral stance assessments in elementary schoolchildren are limited. The present study was designed to report test-retest reliability and reference values for postural stability in 9 to 10 years old schoolchildren using the Balance Master system. MATERIALS AND METHODS: Twenty children participated in the reproducibility study (mean age 10.1+/-0.7) including test and retest measurement with a one-week interval. The modified clinical test of sensory interaction on balance (mCTSIB) quantified children's static standing balance. The test for the limits of stability (LOS) measured dynamic standing balance. The study sample to determine reference values consisted of 99 children (mean age 9.8+/0.5). RESULTS: The ICCs for inter-item reliability of the four sensory conditions of the mCTSIB showed fair to excellent reliability (ICCs between 0.62 and 0.80). The reproducibility between test and retest was non-significant for the condition 'firm surface with eyes closed' (ICC of 0.37), fair to good for the three other sensory conditions (ICCs between 0.59 and 0.68), and excellent for the composite sway velocity (ICC of 0.77). For all LOS parameters, the significant ICCs showed fair to good reproducibility (ICCs between 0.44 and 0.62), with the exception of the non-significant ICC for the composite reaction time. The ICCs for the separate LOS parameters showed fair to good and excellent reliability for nine parameters (ICCs between 0.46 and 0.81), while 11 separate LOS scores did not demonstrate significant ICCs. DISCUSSION: Analysing reference values, girls performed better on all the composite balance parameters compared to boys, with the exception of reaction time and movement velocity. No differences were found on standing balance scores between 9 and 10 year olds. CONCLUSION: In conclusion, the Balance Master showed fair to good reliability for most postural parameters in 9 to 10 year olds. The current data on postural control in children aged 9 to 10 years are relevant for research in other domains within the clinical field, like obesitas and developmental coordination disorder or in relation to back pain prevalence at early age.

Child↗

PubMedDate not supplied

[Vestibular compensation. Rehabilitation of a patient with vertigo].

Vestibular compensation is the association of neurological reorganization events that allow to recover the balance after peripheral vestibular damage. The aim of rehabilitation of the patient with vertigo is to maximize these events to achieve an earlier return of the patients to active life. An individualized vestibular rehabilitation program is used on the basis of a general protocol that includes the following four elements: a) stabilization of vision and coordination of head and eye movements; b) vestibular habituation exercises adapted on an individual basis; c) postural control exercises via biofeedback techniques; and d) a program to improve general patient conditions. It is concluded that rehabilitation therapy of vertigo should always be taken into account, both in balance alterations caused by peripheral vestibular lesions and in central nervous damage and mixed pathology.

Clinical Protocols↗

PubMed1992

Experimental kyphoscoliosis induced in rats by selective brain stem damage.

The relationship between damage to particular brain stem nuclei related to postural control and equilibrium and the occurrence of spinal deformity has been investigated. The model used was the Wistar albino rat and the brain stem structures damaged were the gracillis nucleus, the superior colliculus and the lateral vestibular nucleus. Out of 60 brain stem damaged animals, 44 had accurate lesions from which 11 (25%) showed kyphoscoliotic deformities. Rats with spinal deformity showed an imbalance of the paraspinal muscles when assessed by EMG; this was expressed by an increase of muscular activity on the convex side. This study indicates that postural dysfunction caused by brain stem damage may induce kyphoscoliosis in experimental animals and could be one of the underlying mechanisms in the production of human idiopathic scoliosis.

Animals↗

PubMedDate not supplied

Influence of nicardipine on the blood pressure at rest and on the pressor responses to cold, isometric exertion, and dynamic exercise in hypertensive patients.

The dose-response effects of a new slow-calcium-channel blocker, nicardipine, on the resting blood pressure and on the pressor responses induced by skin cold, isometric exertion, and dynamic exercise were examined in a single-blind placebo-controlled study in six male patients with stable uncomplicated essential hypertension. Nicardipine was administered orally in doses of 5 mg, 10 mg, 20 mg, and 20 mg each given three times daily consecutively for 1 week. At the end of each dose period the effects on blood pressure and heart rate at rest and during the three pressor stimuli were measured. There was a significant dose-related reduction in the resting diastolic blood pressure without change in pulse pressure, accompanied by an increase in heart rate. No postural effects on blood pressure were observed. There was a small reduction in the pressor response to hand cold, which was statistically significant at the higher doses. There was no attenuation of the increases in pressure and heart rate induced by handgrip contraction or submaximal treadmill walking at any dose of nicardipine. These results are compatible with direct relaxing effect of the drug on the smooth muscle of the arteriolar resistance vessels without substantial impairment of the sympathetic influences responsible for postural control of the systemic blood pressure or those involved in the pressor responses to the three stimuli tested.

Adult↗

PubMed2004

Proprioception, kinesthesia, and balance after total knee arthroplasty with cruciate-retaining and posterior stabilized prostheses.

BACKGROUND: The effect of total knee arthroplasty on proprioception, kinesthesia, and postural control remains controversial. It is argued that retaining the posterior cruciate ligament may help to preserve these sensorimotor functions and improve the longevity of the prosthesis and the functional outcome. We performed a prospective, randomized study to assess proprioception, kinesthesia, and balance following total knee arthroplasty with cruciate-retaining and posterior stabilized prostheses. METHODS: Twenty patients scheduled to undergo total knee arthroplasty were randomly assigned to receive either a cruciate-retaining or a posterior stabilized prosthesis. Joint-position sense, the threshold to detect joint motion, and the subject's ability to balance on an unstable platform were assessed prior to and at least six months after the operation. Paired two-tailed t tests (with a level of significance of p < 0.05) were used to assess the effect of the arthroplasty on the preoperative measures for all subjects. Analysis of covariance was performed to identify the effects of prosthetic design. RESULTS: Following total knee arthroplasty, patients detected motion significantly faster and reproduced joint position with less error. The balance index also improved significantly from the preoperative to the postoperative evaluation. The group treated with the posterior stabilized prosthesis more accurately reproduced joint position when the knee was extended from a flexed position. CONCLUSIONS: Total knee arthroplasty results in mild improvements in proprioception, kinesthesia, and balance. These changes may result from the retensioned capsuloligamentous structures and reduced pain and inflammation. Retention of the posterior cruciate ligament does not appear to significantly improve proprioception and balance compared with those functions in patients with a posterior stabilized total knee design.

Aged↗

PubMed2003

Defective balancing ability and hyperactivity in the CLX (circling behavior linked to the X-chromosome) mutant rat.

We have reported that the recently described circling behavior rat (CLX) is a hereditary mutant controlled by a single sex-linked recessive gene (gene symbol: clx). This mutant shows intermittent circle walking and/or running and head tossing with the neck twisted. The abnormal behavior begins to appear around weaning and continues throughout life. In the present study, behavioral tests were performed during the suckling and post-weaning periods and when the rats reached maturity, and the following peculiar abnormalities were revealed: (1) in the righting reflex test, the CLX young show a tendency to take a longer time to revert to normal posture; (2) in the negative geotaxis test, they had difficulty moving upward at 12 days of age; (3) in the air righting reflex test, they frequently fell on their backs or shoulders even after weaning; (4) almost none of the CLX rats showed nystagmus, which is invariably observed in normal rats after rotating stimulation, at 20 weeks of age; and (5) they showed hyperactivity in the open field test at the age of 5 or 6 weeks and a higher degree of locomotor activity in the home cage at the age of 7 and 15 weeks. These results suggest that CLX mutant rats may have some defect in vestibular function (balance sense) or abnormalities in an area of the central nervous system responsible for posture control, e.g., in the dopaminergic or GABAergic neurons.

Animals↗

PubMed1991

Improvement of functional sitting position for children with cerebral palsy.

Twenty-three children with cerebral palsy were photographed and video-filmed in six different sitting positions--including a hypothetical functional position--and the video-films and photographs were analysed. It was found that pathological movements were minimised and postural control and arm and hand function best when the child was sitting in a forward-tipped seat, with a firm backrest supporting the pelvis, arms supported against a table and feet permitted to move backward.

Activities of Daily Living↗

PubMed2004

Organization of area 3a in macaque monkeys: contributions to the cortical phenotype.

The detailed organization of somatosensory area 3a was examined in macaque monkeys using multiunit electrophysiological recording techniques. By examining topographic relationships, changes in receptive field size, and the type of stimulus that neurons responded to, functional boundaries of area 3a were determined and related to architectonic boundaries. One striking observation was that the location of area 3a varied with respect to the central sulcus. In one-half of the cases area 3a was on the rostral bank and fundus of the central sulcus and in the other half of the cases it was on the caudal bank and fundus of the central sulcus. In terms of topographic organization, we found that area 3a contains a complete representation of deep receptors and musculature of the contralateral body, and that the general organization of body part representations mirrors that of the primary somatosensory area, 3b. These results as well as results from studies of area 3a in ours and other laboratories indicate that area 3a is part of a network involved in proprioception, postural control, and the generation of coordinated movements. Further, comparative analysis of area 3a in a variety of species suggests that its construction is based, to a large extent, on the use of a particular body part rather than on innervation density.

Animals↗

PubMed2004

Reliance on visual information after stroke. Part I: Balance on dynamic posturography.

OBJECTIVE: To test the hypothesis that postural imbalance after stroke may be caused by inability to use pertinent somatosensory, vestibular, or visual information. DESIGN: Description of the sensory organization of patients with hemiplegia. SETTING: Public rehabilitation center in France. PARTICIPANTS: Forty patients with hemiplegia after a single hemisphere stroke who were at least 12 months post stroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The patients performed computerized dynamic posturography (EquiTest), which is designed to assess a patient's ability use sensory inputs separately and to effectively suppress inaccurate inputs in case of sensory conflict. Body stability under each of 6 sensory conditions was assessed by an equilibrium score (ES). RESULTS: In conditions of altered somatosensory information, with visual deprivation (ES5) or visuovestibular conflict (ES6), the median scores for patients with hemiplegia (ES5-43; ES6-20) were significantly lower than those for normal subjects (ES5-69; ES6-67). CONCLUSIONS: Many patients with hemiplegia seem to rely on visual input. The mechanism of this excessive visual reliance is discussed. Rehabilitation programs of postural control for the patients with hemiplegia should take into account the possible impairment of sensory organization and should include exercises to be performed under conditions of sensory input deprivation and sensory conflict.

Cerebral Cortex↗

PubMedDate not supplied

Hip sway associated with vestibulopathy.

We identify a population of patients with vestibular complaints who show excessive hip sway and center of gravity movement during clinical balance testing. To determine the postural control strategy used by these patients, the body movement and muscle activation patterns of 9 patients responding to backward support surface translations were studied. Patients' responses were compared to those of normal subjects tested both under the same conditions and while using hip sway to balance across a narrow beam. Unlike normal subjects responding to translations of a flat support surface, all patients showed hip movement patterns that kinematically resembled the movements of normal subjects balancing across a beam. Although all patients showed the same body movement patterns, they showed two different muscle activation patterns, neither of which was similar to those of normal subjects responding to flat support surface translations. Four patients showed bursts in abdominal and/or quadriceps muscles characteristic of active hip flexion to move the center of mass, although the timing of these bursts was variable. The remaining 5 patients showed minimal activation of any proximal muscles, suggesting a failure to control upper body motion resulting from activation of ankle muscles. To determine whether the excessive hip sway observed in these patients could be a voluntary response to platform translation, the patients' responses were compared to those of a second group of normal subjects voluntarily responding to backward support surface translations with hip sway. Unlike the patients, all normal subjects responding voluntarily consistently activated abdominal muscles slightly later than ankle muscles. It is therefore unlikely that the patients' responses to platform translations were simply voluntary responses. Thus, vestibular deficits can result in abnormally coordinated postural movement strategies that result in excessive hip sway.

Adolescent↗

PubMed2001

Nonlinear dynamics of human postural sway during upright stance.

We present a procedure for characterizing the postural sway during quiet upright stance using methods of nonlinear dynamics. The displacements of the centre of foot pressure in anterior-posterior and lateral directions were measured using a force platform. We examined the changes of the postural control mechanisms when visual or proprioceptive information are reduced. We applied four analytic procedures to test the nature of posturographic time series: Kolmogorov-Smirnov test for amplitude distribution; shapes of autocorelation functions; structure functions and log-log plots of power spectra. Nongaussian distribution and nonlinear dynamics were established by all tests. The power spectra (PS) exhibited an exponential decreasing shape, which is commonly referred to as "1/f noise". The fractal structure of the process was characterised by fractal dimension (Df) and shape of structure functions. Our results show that the maintenance of postural stability in upright stance and reduced sensory inputs is nonlinear dynamic process with fractal structure.

Adult↗

PubMed1998

Normal variability of postural measures: implications for the reliability of relative balance performance outcomes.

The reliability of outcome measures obtained using the Balance Master and the limits of stability in anterior, posterior, and lateral directions were evaluated in 70 healthy subjects aged 20 to 32 years. Data relating to static sway and the ability to shift the centre of gravity to preset targets were collected on three occasions one week apart. The centre of gravity position and limits of stability were determined over three trials and data converted from a relative reference system to absolute displacements from vertical. Intraclass correlation coefficients revealed fair to poor reliability of static and dynamic sway measures (coefficients < or = 0.55) and excellent reliability of limits of stability measures and the position of the centre of gravity (coefficients > or = 0.75). The variability in outcome measures from tests which do not maximally challenge the postural control system may be a hallmark of normal balance performance. Further, the intersubject variation in resting centre of gravity position and in limits of stability supports the use of absolute performance measures as the interpretive value of data expressed relative to standard norms is limited.

Adult↗

PubMed1997

Postural responses to vibration of neck muscles in patients with idiopathic torticollis.

Vibration of the dorsal muscles of the neck, simulating lengthening, in standing man causes a visible forwards tilt of the body shown on posturography as a tonic sagittal sway deviation. According to the theory that posture is organized with respect to a 'body schema' this deviation is a result of an interpretation of the concurrent neck afferent and vestibular signals. Considering the hypothesis that neck afferent signals may be misinterpreted in patients with spasmodic torticollis (ST) causing abnormal postural responses, we recorded body sway induced by unilateral dorsal neck muscle vibration in 22 idiopathic ST patients (19 treated with botulinum toxin) during upright stance with eyes closed. Comparison groups were 19 normal subjects and 11 patients with bilateral loss of vestibular function (labyrinthine defective, LD) in whom neck afference should be intact. Both treated and untreated ST and LD patients had absent or diminished sway deviations. When sway deviation did occur, it was sagitally oriented as with normal subjects and unrelated to ST head turns. In most ST and LD patients, neck vibration induced neck extension, an effect which is observed in normal subjects only if the torso is retrained. The results suggest that neck proprioceptive input retains local postural functions in ST, however, it is relatively ignored in the context of the whole body postural control and spatial orientation. The mild disorders of vestibular function reported in torticollis patients may be due to an inability to calibrate vestibular signals by reference to corroborative signals from neck proprioception.

Achilles Tendon↗

PubMed1984

Electromyographic results of inhibitory splinting.

The purpose of this study was to compare the integrated EMG activity of spastic muscles in brain-damaged patients before and during splint application. Eight patients with spasticity that produced limb posturing were systematically monitored for EMG activity during a two-hour interval without a splint (Nonsplinted Condition), and during a subsequent two-hour period while wearing the splint (Splinted Condition). The goniometric measurement of the limb position also was taken during the two conditions. The limb postures monitored were ankle plantar flexion, wrist flexion, and elbow flexion. A paired t test showed a significant (p less than .001) increase in the position of the limb into extension in the Splinted Condition compared with the Nonsplinted Condition. No significant reduction in integrated EMG activity occurred during the Splinted Condition compared with the Nonsplinted Condition. Despite the significant change in joint position and elongation of spastic muscles produced by the splinting, the muscle groups accommodated to the position as evidenced by the lack of significant change in EMG activity. Therefore, splinting can effectively control postural defects caused by spastic limb posturing without significantly increasing muscle tone. Implications of the results and the use of EMG measurement to help identify patient candidates for splinting are discussed.

Adolescent↗

PubMed2004

Discriminating between elderly and young using a fractal dimension analysis of centre of pressure.

The aim of this project was to evaluate the use of a new analysis technique, fractal dimension analysis, for quantification of quiet stance centre of pressure (COP). By using a fractal dimension analysis of COP, it might be possible to gain more information about control during quiet stance than traditional analyses have previously allowed. The current project considered a group of young healthy participants and a group of elderly healthy participants to compare traditional measures of COP against a fractal dimension analysis of COP. Results indicated that both types of analyses are able to distinguish between eyes open and eyes closed in the elderly group. However, the fractal dimension analysis more accurately detected differences between the participant groups when standing with their eyes closed. Based on these results it is suggested that fractal dimension analysis is more informative about posture control than traditional measures. It is suggested that a fractal dimension type of analysis can be incorporated into clinical testing to identify patients with pathologies.

Journal Article↗

PubMed1999

Arm raising in humans under loaded vs. unloaded and bipedal vs. unipedal conditions.

The aim of the present experiment was to study the central organization of equilibrium control during arm raising in the frontal plane. Nine adult subjects (five seniors and four young adults) were asked to raise their right arm to a horizontal position in the frontal plane in two support conditions (bipedal vs. unipedal) and two load conditions (unloaded vs. a 3.5-kg load added on the moving hand). No instructions were given concerning the movement speed. The movements were performed at about half the maximum speed achievable under reaction time conditions. The final lateral center of mass (CM) position 1 s after the movement offset, and the time course of the CM shift during the movement were studied in the four experimental conditions, using a CM compensation index. The electromyographic (EMG) pattern of the main muscles involved in the movement performance and in the postural control were studied in three out of nine subjects during movements performed at two velocities (at the preferred speed and as fast as possible). The results indicate that (1) the CM shift remains minimized in the frontal plane during the time course of the arm movement and during the final stabilization of the arm regardless of the stance and load conditions; (2) the time course of the CM compensation index remains stable during the first 400 ms after the movement onset, decreasing late in the movement and increasing again at the end of the stabilization stage. A modelisation suggests that the time course is the result of the interaction of two controls: a first one, putative feedforward, starting early and decreasing with time and a second one, putative feedback, starting late in the movement and increasing with time; (3) both early and late index values are influenced by the support and load conditions, the highest index values being observed during unipedal stance and load conditions; (4) activation of quadratus lomborum (QL) contralateral to the raising arm is time locked with the deltoidus activation of the raising arm in both fast and slow movements: this contralateral QL activation corresponds to an anticipatory postural adjustment (APA) aimed at minimizing the CM shift.

Adult↗

PubMedDate not supplied

An exploration of German and British physiotherapists' views on the effects of hippotherapy and their measurement.

Hippotherapy (Greek hippos = horse) is a specialised physiotherapy treatment that makes use of the horses' unique three-dimensional movement impulses at a walk to facilitate movement responses in patients sitting on the horse's back (Strauss, 2000). Despite a substantial body of anecdotal and clinical evidence for its benefits, research evidence for hippotherapy is sparse. This questionnaire survey was the first study in a series of investigations exploring the views of physiotherapists and people with cerebral palsy who use hippotherapy. These investigations, in turn, form the basis from which the authors will recommend outcome measures for individuals with cerebral palsy in a hippotherapy environment. This study aimed to: (a) establish the pattern of hippotherapy practice in Germany and the U.K.; (b) examine the perceived main effects of hippotherapy on people with cerebral palsy in Germany and the U.K.; and (c) investigate how these effects are being measured in both countries. The results highlighted considerable differences in how hippotherapy is practised in the U.K. compared with in Germany. In spite of this, the study revealed agreement among respondents on the overall perceived effects of hippotherapy on individuals with cerebral palsy, namely, the regulation of muscle tone, improvement of postural control and psychological benefits. The results also indicate scant use of outcome measures to evaluate these effects. The impact of these findings is discussed in the light of published research, and suggestions for further research are made.

Animals↗