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At least 469 records · Page 26Linked to original sources
PubMed2000

Postural control in rheumatoid arthritis patients scheduled for total knee arthroplasty.

OBJECTIVE: To investigate the use of compensatory visual and attentional control strategies for standing balance in patients with rheumatoid arthritis (RA) with severe knee joint impairment. DESIGN: Experimental 2-group design. SETTING: Specialized clinic for orthopedics, rheumatology, and rehabilitation in The Netherlands. PARTICIPANTS: Eighteen patients without comorbidity (age range, 65 +/- 7.7 yr; 16 women, 2 men) from a consecutive sample of patients with RA scheduled for total knee arthroplasty; 23 controls of the same age group also were tested (13 women, 10 men). MAIN OUTCOME MEASURES: By means of a dual-plate force platform, the velocity of center of pressure (COP) fluctuations were analyzed in the anteroposterior and lateral sway directions during quiet standing with eyes open, eyes closed, and while performing a secondary attention-demanding arithmetic task. RESULTS: Patients showed an average 80% greater COP velocity in both directions of sway compared with controls. In addition, stability deteriorated substantially more in patients than controls when deprived of visual information, which was associated with the degree of knee destruction. The effect of the arithmetic task was small and similar in patients and controls. CONCLUSION: RA patients with severe knee joint impairment can have a substantial basic postural instability; their relatively high reliance on visual information suggests impaired sensory feedback from the lower limbs. Current research is aimed at determining whether these postural deficits can be improved by total knee replacement.

Activities of Daily Living↗
PubMed1991

Baroreceptor reflexes in postural control of circulation in rabbits.

The present study was undertaken to evaluate reflex cardiovascular responses to postural stress in rabbits. The changes in mean arterial pressure (MAP) and heart rate (HR) were monitored in the supine position and following sudden passive head up tilt (HUT), and head down tilt (HDT) to 70 degrees. The results show a significant increase in MAP (18.57%, P less than 0.001) and HR (2.92%, P less than 0.02) with HUT; and a marked decrease in MAP (43.48%, P less than 0.001) and HR (8.21%, P less than 0.001) with HDT (as compared to the values in supine position). The changes in MAP were found to be more marked than those in HR. The depressor responses to HDT were more marked than the pressor responses to HUT.

Animals↗
PubMed1997

Postural control of three-dimensional prehension movements.

This experiment was carried out to test the hypothesis that three-dimensional upper limb movements could be initiated and controlled in the joint space via a mechanism comparing an estimate of the current postural state of the upper arm with a target value determined by one specific inverse static transform converting the coordinates of the object into a set of arm, forearm, and wrist angles. This hypothesis involves two main predictions: 1) despite joint redundancy, the posture reached by the upper limb should be invariant for a given context; and 2) a movement programmed in joint space should exhibit invariant characteristics of the joint covariation pattern as well as a corresponding variable hand path curvature in the task space. To test these predictions, we examined prehension movements toward a cylindrical object presented at a fixed spatial location and at various orientations without vision of the moving limb. Once presented, the object orientation was either kept constant (unperturbed trials) or suddenly modified at movement onset (perturbed trials). Three-dimensional movement trajectories were analyzed in both joint and task spaces. For the unperturbed trials, the task space analysis showed a variable hand path curvature depending on object orientation. The joint space analysis showed that the seven final angles characterizing the upper limb posture at hand-to-object contact varied monotonically with object orientation. At a dynamic level, movement onset and end were nearly identical for all joints. Moreover, for all joints having a monotonic variation, maximum velocity occurred almost simultaneously. For the elbow, the only joint presenting a reversal, the reversal was synchronized with the time to peak velocity of the other joint angles. For the perturbed trials, a smooth and complete compensation of the movement trajectory was observed in the task space. At a static level the upper limb final posture was identical to that obtained when the object was initially presented at the orientation following the perturbation. This result was particularly remarkable considering the large set of comfortable postures allowed by joint redundancy. At a dynamic level, the joints' covariation pattern was updated to reach the new target posture. The initial synergies were not disrupted by the perturbation, but smoothly modified, the different joints' movements ending nearly at the same time. Taken together, these results support the hypothesis that prehension movements are initiated and controlled in the joint space on the basis of a joint angular error vector rather than a spatial error vector.

Adult↗
PubMed2005

[Effect of physical training on postural control of elderly].

BACKGROUND: Preservation of balance in the elderly is fundamental to maintaining functional independence. Balance impairments have a tremendous impact on health care costs and quality of life. Fall prevention programs are an important health strategy, consequently there is a general need to develop effective and practical exercise programs that improve balance in the elderly. OBJECTIVE: To explore whether stability can be improved through exercise in inactive old subjects and to determine whether specific balance training proves to be more beneficial to retaining balance than strength training. METHODS: A randomized controlled study was conducted with 42 healthy elderly individuals. They were randomly allocated to three groups: Balance training (BT), Isometric training (IT) and Control (CG) received no intervention; each group consisted of 14 members. "Static" and "dynamic" postural stability were evaluated for seven postural conditions in upright standing before and immediately after 3 months of intervention using a force platform, and an isokinetic dynamometer used to determine whether the training improved muscle strength. RESULTS: The BT group significantly improved their forward-backward stability limits (maximal body lean) post intervention compared with other groups. Plantar and dorsiflexion isometric strength remained the same in all groups. No significant improvement was found in COP based measures in upright standing in all study groups, apart from the BT group that significantly improved parameters in performance with eyes open and during standing on a foam. BT subjects improved their self-confidence post intervention in 64.2%, while IT subjects improved in only 35.7%. CONCLUSIONS: Balance exercises appear to improve balance in the elderly, especially extending the boundaries of their stability a more dynamic component of balance. However it remains to be determined whether the lack of difference between groups in COP measures in upright standing ("static balance") was due to the short period of intervention, small sample size, unchallenged exercise regime or due to the inability of elderly individuals to improve their sway in upright standing.

Aged↗
PubMed2000

Perception of surrounding space controls posture, gaze, and sensation during Coriolis stimulation.

BACKGROUND: Motion sickness evokes not only discomfort but also marked equilibrium ataxia. However, its mechanism of ataxia remains unclear. HYPOTHESIS: We supposed that stance, gaze, and sensation may be uniformly controlled by the perception of the surrounding space. METHODS: Using Coriolis stimulation, we examined eight normal subjects and two patients with bilateral labyrinthine loss. They were asked to stand on a platform; then while being rotated clockwise 60 degrees x s(-1), they tilted their head 30 degrees. Displacement of the center of pressure and ocular movements were recorded using a force platform set on the device and an infrared CCD-video camera fixed to goggles, respectively. RESULTS: In normal subjects with eyes covered, tilting of the head resulted in shifts of the center of pressure and torsional or vertical nystagmus. When they could see the surroundings, they showed stable posture and optokinetic nystagmus regardless of head tilting status. In contrast, the two patients were not affected by head tilting when their eyes were covered, although they showed remarkable body swaying even while they were static. CONCLUSIONS: From the present study, it seems probable that posture, gaze, and sensation are absolutely controlled by the perception of surrounding space, which may be theoretically represented as a vector in the head.

Adult↗
PubMed2001

Postural control of the trunk in response to lateral support surface translations during trunk movement and loading.

The postural response to translation of the support surface may be influenced by the performance of an ongoing voluntary task. This study was designed to test this proposal by applying lateral perturbations while subjects handled a load in the frontal plane. Measurements were made of medio-lateral displacement of the centre of pressure, angular displacement of the trunk and thigh in the frontal plane and intra-abdominal pressure. Subjects were translated randomly to the left and right in a variety of conditions that involved standing either quietly or with a 5 kg load in their left hand, which they were required either to hold statically or to lift or lower. The results indicate that when the perturbation occurred towards the loaded left side the subjects were able to return their centre of pressure, trunk and thigh rapidly and accurately to the initial position. However, when the perturbation occurred towards the right (away from the load) this correction was delayed and associated with multiple changes in direction of movement, suggesting decreased efficiency of the postural response. This reduced efficiency can be explained by a conflict between the motor commands for the ongoing voluntary task and the postural response, and/or by the mechanical effect of the asymmetrical addition of load to the trunk.

Abdomen↗
PubMed2001

The effect of expertise in gymnastics on postural control.

The goal of this paper was (1) to investigate if gymnasts have a more stable standing posture than experts in other sports, and (2) to determine how much gymnasts are affected by the removal of vision in different postural tasks. Six expert gymnasts and six experts in other non-gymnastic sports were asked to maintain balance in three standing postures of increasing difficulty: bipedal, unipedal, and unipedal + unstable support (i.e. 7 cm thick foam surface). Each posture was tested successively with and without vision. Based on the displacement of the center of pressure (range and mean average speed), the results showed that when visual cues were available, postural sway increased with the difficulty of the task, but both groups had comparable performance in all the tasks. When vision was removed, although both groups demonstrated larger postural sway in the unipedal tasks, this effect was less accentuated for the gymnasts. We concluded that gymnasts are able to use the remaining sensory modalities to compensate for the lack of vision in unstable postures.

Adult↗
PubMed1986

Compensation effect of visual biofeedback in upright posture control.

The effectivity of the compensatory role of visual biofeedback in cases of decreased stability of upright posture has been analysed. The deterioration of stance was modelled by a subject standing on a soft surface and with additional weight load on the body. The influence of visual biofeedback was positive only for the compensation of decreased stability of upright posture caused by artificially increased body weight of the subject. The compensatory effectivity of visual biofeedback in stabilization of upright posture during stance on a soft surface was practically negligible. The results have shown that effective compensation of the destabilizing effect by visual biofeedback in human upright posture was possible only when the activity and efficiency of efferent-action part of the postural system remained unchanged.

Adult↗
PubMed2002

Effect of cognitive load on postural control.

The present study reports findings from two experiments on the relation between a mental task (silent backward counting) and posture. The first experiment included 30 normal subjects and the second experiment 20 normal subjects. In Experiment 1 postural sway and performance of the mental task were measured in a 2 x 2 dual-task design (with or without mental task and calf stimulation). In Experiment 2 a similar design was used, the only difference being that during trials without the mental task, subjects were instructed to focus on their balance and provide a rating of body sway. Results showed that balance perturbation led to decreased performance on the cognitive task in Experiment 1, but not in Experiment 2. The mental task led to less body sway, while focused attention attenuated the effect. In conclusion, control of body sway and cognitive functioning are to some extent related.

Adult↗
PubMed1998

Development of postural control of gravity forces in children during the first 5 years of walking.

The aim of this work was to propose developmental indexes relative to the control of balance and gravity forces, using force-plate data, for children in their first 5 years of independent walking. The first part of this paper is devoted to the definition of an index to quantify postural capacity during walking. Based on the assumption that the vertical acceleration of center of mass (CM) reflects the capacity of muscular forces between the head-arms-trunk and the stance leg segments to control the external forces, the value of the CM vertical acceleration at foot contact is proposed as a developmental index of the postural capacity of the child to control gravitational forces. This index was analyzed longitudinally in five children, over the course of eight experimental sessions. The children were examined during their first 5 years of independent walking (for a total of 457 step sequences). The covariation between the CM vertical acceleration at foot contact and the gait velocity was considered as a second index characterizing the development of coordination between the postural and dynamic requirements of body progression. From these indexes it was established that the postural capacity needed just to control balance with the leg muscles was not attained before 4-5 years of independent walking, i.e., at about 5-6 years of age.

Acceleration↗
PubMed2005

Postural control in patients with unilateral vestibular lesions is more impaired in the roll than in the pitch plane: a static and dynamic posturography study.

The postural instability of patients with vestibular loss (11 with bilateral and 101 with unilateral vestibular loss) at different times following the lesion was investigated by means of posturography and compared to healthy subjects. In addition, subjects submitted to galvanic vestibular stimulation were also studied to compare their postural performances with those of patients with complete unilateral vestibular lesion. The platform consisted of a static computerized force platform, on which a seesaw platform could be placed to test the subjects in dynamic conditions. The displacement of the center of foot pressure was measured under different conditions: subjects standing on the fixed platform, eyes open and eyes closed and subjects standing on the seesaw platform, eyes open and eyes closed. In the last condition, balance was tested in the subject's pitch plane by allowing the platform to rotate forwards and backwards only and in the patient's roll plane by allowing the platform to rotate to the left and to the right. The results showed that in static conditions, only bilateral vestibular loss patients had abnormal values compared to controls. In contrast, in dynamic eyes-closed conditions, both bilateral and unilateral patients could be differentiated from controls. Bilateral patients were unable to stand up without falling in both pitch and roll planes. Unilateral patients fell in the first week following the lesion and exhibited increased postural oscillations in both planes from the 2-week up to the 1-year postlesion stage. In addition and more importantly, they fell more often or had higher sway in the roll than in the pitch plane. Therefore, this study suggests that dynamic posturography on a seesaw platform could be a valuable tool for clinical diagnosis and quantitative analysis of imbalance in patients suffering from a unilateral vestibular loss up to 1 year after the lesion.

Accidental Falls↗
PubMed1996

Postural control in children with spastic diplegia: muscle activity during perturbations in sitting.

To clarify the neural mechanisms controlling equilibrium during sitting, and the implications for the optimal sitting position for children with CP, automatic postural adjustments after perturbations of the support surface during sitting were investigated in seven children with spastic diplegia and in seven age-matched controls. A sudden backward sway of the body evoked brisk responses in ¿ventral' muscles in both groups. However, the order of muscle recruitment, which in most non-disabled children was caudal, was reversed in the children with diplegia, whose first response was in the neck flexors. The children with diplegia also co-activated antagonistic neck and hip muscles. The authors concluded that although children with spastic diplegia may produce a basic muscle activation pattern (first level of the central pattern generator, CPG), they cannot adjust the pattern in response to external changes (second level of the CPG).

Cerebral Palsy↗