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At least 1,639 records · Page 91Linked to original sources
PubMed1999

Increased body sway at 3.5-8 Hz in patients with phobic postural vertigo.

Postural sway during upright stance was analyzed in 12 patients with phobic postural vertigo (PPV) and in 12 age-matched healthy volunteers. Recordings were made under different conditions (with the eyes open or closed): when standing on a foam rubber pad with the head upright, turned 30 degrees to the right or left, or during 1 Hz horizontal head oscillations. Sway analysis included calculation of sway path, of root mean square values of sway and of the power spectrum of sway in fore/aft and lateral directions. There was a significant increase in sway activity in the 3.53-8 Hz frequency band in patients with PPV. This did not impair objective postural stability. Increase in higher frequency sway activity may simply reflect a change in postural strategy rather than a sensorimotor dysfunction. The patients' conscious control of stance may augment co-activation of anti-gravity muscles, a strategy applied by normal subjects when performing demanding balancing tasks.

Adult↗
PubMed2003

Neck muscle fatigue affects postural control in man.

We hypothesised that, since anomalous neck proprioceptive input can produce perturbing effects on posture, neck muscle fatigue could alter body balance control through a mechanism connected to fatigue-induced afferent inflow. Eighteen normal subjects underwent fatiguing contractions of head extensor muscles. Sway during quiet stance was recorded by a dynamometric platform, both prior to and after fatigue and recovery, with eyes open and eyes closed. After each trial, subjects were asked to rate their postural control. Fatigue was induced by having subjects stand upright and exert a force corresponding to about 35% of maximal voluntary effort against a device exerting a head-flexor torque. The first fatiguing period lasted 5 min (F1). After a 5-min recovery period (R1), a second period of fatiguing contraction (F2) and a second period of recovery (R2) followed. Surface EMG activity from dorsal neck muscles was recorded during the contractions and quiet stance trials. EMG median frequency progressively decreased and EMG amplitude progressively increased during fatiguing contractions, demonstrating that muscle fatigue occurred. After F1, subjects swayed to a larger extent compared with control conditions, recovering after R1. Similar findings were obtained after F2 and after R2. Although such behaviour was detectable under both visual conditions, the effects of fatigue reached significance only without vision. Subjective scores of postural control diminished when sway increased, but diminished more, for equal body sway, after fatigue and recovery. Contractions of the same duration, but not inducing EMG signs of fatigue, had much less influence on body sway or subjective scoring. We argue that neck muscle fatigue affects mechanisms of postural control by producing abnormal sensory input to the CNS and a lasting sense of instability. Vision is able to overcome the disturbing effects connected with neck muscle fatigue.

Adult↗
PubMed1998

Relationship between postural control and motion sickness in healthy subjects.

This study examined the relationship between reported susceptibility to motion sickness, anxious personality and postural control. Postural stability was assessed in 34 healthy subjects standing with eyes open, eyes closed and viewing a disorienting virtual reality display. These measures were repeated with vibration of the calf muscles to distort the somatosensory feedback from the legs. Susceptibility to motion sickness and anxious personality were evaluated by questionnaire. Greater postural instability was correlated with susceptibility to motion sickness. Motion sickness susceptibility correlated most strongly with increased sway when the visual and somatosensory feedback was absent or distorted. Anxiety was correlated with reported susceptibility to motion sickness but not with postural stability. These findings suggest that deficient perceptual-motor responses to disorienting conditions may contribute to motion sickness susceptibility.

Adult↗
PubMed1998

Postural instability precedes motion sickness.

We evaluated the hypothesis that postural instability precedes the onset of motion sickness. Subjects standing in a "moving room" were exposed to nearly global oscillating optical flow. In the experimental condition, the optical oscillations were a complex sum-of-sines between 0.1 and 0.3 Hz, with an excursion of 1.8 cm. This optical motion was of such low frequency and magnitude that it was sometimes not noticed by subjects. However, in two experiments, exposure to the moving room produced significant increases in scores on a standard motion sickness questionnaire. In addition, approximately half of subjects reported motion sickness. Analysis of postural motion during exposure to the moving room revealed increases in postural sway before the onset of subjective motion sickness symptoms. This confirms a key prediction of the postural instability theory of motion sickness.

Adaptation, Physiological↗
PubMed1997

Posture, spontaneous movements, and behavioural state organisation in infants affected by brain malformations.

Posture, quantity of spontaneous movement patterns, quality of general movements (GMs), and behavioural state organisation were studied in nine infants affected by documented brain malformations. A single 1 h video recording of five infants and two or more serial video recordings of another four infants were performed after birth. The graphic representation of single movement patterns (actogram) and of behavioural states of one video recording was performed in eight out of nine infants. The quality of GMs was assessed according to Prechtl's method in all video recordings. All nine infants showed a less variable posture than normal newborn infants and an unusual resting posture was detected in seven infants. Poor behavioural state organisation without sleep cycles was common to the nine infants and excessive wakefulness was observed in six infants. As for the quantity of single movement patterns, six infants lacked one or two movement patterns normally present in healthy newborn infants. An abnormal quality of GMs was noted in all nine infants and distinct motor abnormalities were observed in single infants. A monotonous and sometimes stereotyped sequence of different body parts involved in the movement (i.e. poor repertoire GMs) was common to all infants. In the four infants of whom two or more video recordings were available, initial poor repertoire GMs were followed by a further deterioration in movement quality. No relationship was found between the quantity of defective brain tissue, lack of a specific part of the brain, type and severity of GM and posture abnormalities.

Brain↗
PubMed2001

Readiness to adopt adequate postural habits: an application of the Transtheoretical Model in the context of back pain prevention.

Based on a biomechanical model, an adequate body posture can contribute to the prevention of back pain and back pain chronicity. This study examines the explanatory value of the Transtheoretical Model (TTM) for the adoption of adequate postural habits in a cross-sectional sample of 149 employees of a German administration unit (mean age 40.2 years, 50% female). Using newly developed instruments with satisfactory psychometric properties, basic assumptions of the TTM could be confirmed: self-efficacy and the perceived pros for maintaining a good body posture increased significantly across the stages, while the perceived cons decreased. Additionally, the use of preventive strategies for back pain prevention increased linearly and significantly across the stages of change. The study supports the applicability of the TTM for postural behavior. Considering stages of change as an intervening variable may contribute to clarifying the relationship between participation in low back schools and prevention of back pain chronicity. Longitudinal and intervention study data are needed to support these assumptions.

Adult↗
PubMed1997

[Dynamic postural adjustments associated with the development of isometric forces in sitting subjects].

The present study was undertaken to determine whether dynamic postural adjustments in sitting subjects occur during the development of isometric forces and whether the performance, i.e., the maximal isometric force, is related to the surface of contact of the ischio-femoral region with the seat. The subjects were asked to exert maximal horizontal two-handed isometric pushes on a bar. External force (Fx), antero-posterior reaction force (Rx) and antero-posterior displacement of the center of pressure (Xp) were measured continuously during the development of isometric forces, the subsequent hold state lasting 5 s. Two postural conditions were studied that differed by the ischio-femoral contact with the seat (100 or 30%), the foot support being bipodal (BP). It was observed that: a) Fx and Rx increased during the development of isometric forces while Xp moved backwards; b) the instantaneous variations in Fx, in relation to Rx and Xp were linearly related; c) the maximal force reached at the end of the ramp effort and the maximal values of Rx and Xp were significantly increased when the ischio-femoral contact was reduced from 100 to 30 BP. It is concluded that isometric ramp efforts are accompanied by dynamic postural adjustments and that the greater these adjustments, the larger the maximal isometric force. These observations are interpreted as supporting the view that any variation in the external force perturbs the balance of the subject, and that the maximal value of this force depends on the intensity of the dynamic postural counter-perturbation.

Adult↗
PubMed1997

Evidence of a preprogrammed deactivation of the hamstring muscles for triggering rapid changes of posture in humans.

Normal subjects were asked to make rapid flexions of the legs from a stationary initial standing posture in a self-paced mode. Because this movement implicates a rapid change in posture, questions were asked about the type of central command which must include the rupture of the erect posture and the accomplishment of the goal directed movement. Movements of the different segments of the body were recorded and analyzed using the optoelectronic ELITE system. Electromyographic (EMG) activities of 8 muscles of the lower limb on one side were recorded, rectified and integrated. The time relationships of the different EMG signals (activation or deactivation) were analyzed with respect to selected kinetic measures of the related segments of the body. In the majority of the subjects, before the movement onset, EMG events included a specific deactivation of the tonic EMG activity of the semimembranous (SM) and semitendinous (ST) muscles (time onset relative to the onset of the legs flexion: -196.9 +/- 96.4 ms and -180.5 +/- 89.7 ms, respectively). A second event was a phasic activation of the tibialis anterior (TA) muscle (time onset: -60.5 +/- 117.6 ms). Conjugate cross-correlation analysis of these EMG signals demonstrated the existence of a common coordinated strategy between the deactivation of the hamstring and the TA activation. Even though a small horizontal displacement of the head was recorded prior to leg movement, it occurred too late to induce deactivation of the hamstring muscles. These results demonstrate that for rapid legs flexion, where the gravity forces are the main source of joint angle acceleration, the deactivation of the SM and ST muscles acts in conjunction with the phasic activation of the TA. The preprogrammed deactivation of the SM and ST muscles represents the early phase of the central command to switch from the standing to the squatting posture.

Adult↗
PubMed2000

Ultrasonographic evaluation of the influence of different postures on diaphragmatic motion in mechanically ventilated patients.

We confirmed a diaphragmatic motion during mechanical ventilation in four patients with central nervous system damage. The right hemidiaphragm were visualized with 3.5 MHz ultrasound, and motion was measured using time-motion analysis in separate postures. The dome was most impaired during the right decubitus posture. The crural region was most improving during the left decubitus posture. The costal region was most impaired during the sitting posture. The motion of the dependent region was impaired.

Adolescent↗
PubMed2000

Methods for evaluation of postural control adaptation.

New methods were developed to determine the dynamic changes of postural control during the initial exposure to large perturbances of stance. The adjustments of postural control over time in measured anteroposterior torque, were investigated in ten normal subjects. Perturbations of stance were evoked by two high intensity vibrators applying pseudorandom stimulation either to the calf muscles or the paravertebral muscles of the neck. The new methods use a system identification approach, which distinguishes between feedback control, adaptation of postural responses and adaptation to stimulus. This approach makes it possible to quantify motion dynamics and complexity, stimulus impact and adjustments of postural control. Quantification of the different adaptive responses could be useful for diagnostic purposes, in evaluating treatment efficacy and patient progress in rehabilitation programs.

Adaptation, Physiological↗
PubMed2001

Anticipatory postural adjustments associated with lateral and rotational perturbations during standing.

We studied the role of different leg and trunk muscle groups in the generation of anticipatory postural adjustments (APAs) prior to lateral and rotational perturbations associated with predictable and self-triggered postural perturbations during standing. Postural perturbations were induced by a variety of manipulations including catching and releasing a load with the right hand extended either in front of the body or to the right side, performing bilateral fast shoulder movements in different directions, and applying brief force pulses with a hand against the wall. Perturbations in a frontal plane ("lateral perturbations") were associated with significant asymmetries in APAs seen in the right and left distal (soleus and tibialis anterior) muscles; these asymmetries dependent on the direction of the perturbation. Rotational perturbations about the vertical axis of the body generated by fast movements of the two shoulders in the opposite directions were also associated with direction-dependent asymmetries in the APAs in soleus muscles. However, rotational perturbations generated by an off-body-midline force pulse application were accompanied by direction-dependent asymmetries in proximal muscle groups, but not in the distal muscles. We conclude that muscles controlling the ankle joint play an important role in the compensation of lateral and rotational perturbations. The abundance of muscles participating in maintaining vertical posture allows the control system to use different task-dependent strategies during the generation of APAs in anticipation of rotational perturbation.

Adult↗
PubMedDate not supplied

[Repercussion on the hemodynamic measurements across a Swan-Ganz catheter with the postural changes].

AIM: Usually hemodynamic measures are done with the patient in dorsal decubitus and the bedside at 0 degrees. Our aim has been to evaluate the influence that postural changes has in the hemodynamic measures which were carried out with a pulmonary artery catheter, so as called Swan-Ganz. MATERIAL AND METHOD: It's a prospective study. The same patient is control group and study group. There were done tree consecutive measures in each patient. Firstly in dorsal decubitus, then right lateral decubitus and finally in left lateral decubitus. Before doing the measures after change of posture a thirty minutes period was left in order to stabilise the hemodynamical flow. The items of study were, a part of demographic ones, cardiac index, pulmonary artery systolic pressure, pulmonary artery diastolic pressure, pulmonary artery mean pressure, pulmonary artery occlusion pressure, right atrial pressure, systolic arterial pressure, diastolic arterial pressure, mean arterial pressure and heart rate. 28 patients were included in the study. RESULTS: The age average was 62.5 years (27.05-67.05); a 78.6% were male. Who had a NEMS average of 42.4 (39.9-44.9). No difference was found between hemodynamic measures in the different postures. CONCLUSIONS: Postural changes in stable patients have no influence in pressures and other hemodynamic variables measures.

Adult↗
PubMed2003

Body posture affects electroencephalographic activity and psychomotor vigilance task performance in sleep-deprived subjects.

OBJECTIVE: This study examined the effects of posture on electroencephalographic (EEG) activity and psychomotor vigilance task (PVT) performance in 16 sleep-deprived volunteers. METHODS: EEG data were collected while participants completed 10 min PVTs under two counterbalanced sitting/standing conditions during 28 h of continuous wakefulness. RESULTS: In both the sitting and standing conditions, theta activity progressively increased as a function of sleep loss, but standing upright significantly attenuated this effect, suggesting that alertness was improved by the more upright posture. The PVT results showed that cognitive psychomotor performance was maintained at nearly well-rested levels by standing upright, whereas reaction time and attention noticeably deteriorated when participants were seated. CONCLUSIONS: These results suggest that an upright posture increases EEG arousal and sustained attention, indicating that postural manipulations can be useful for counteracting fatigue in sleep-deprived individuals.

Adult↗
PubMed2000

Nonlinear measures of heart rate time series: influence of posture and controlled breathing.

In this study, we investigated measures of nonlinear dynamics and chaos theory in regards to heart rate variability in 27 normal control subjects in supine and standing postures, and 14 subjects in spontaneous and controlled breathing conditions. We examined minimum embedding dimension (MED), largest Lyapunov exponent (LLE) and measures of nonlinearity (NL) of heart rate time series. MED quantifies the system's complexity, LLE predictability and NL, a measure of deviation from linear processes. There was a significant decrease in complexity (P < 0.00001), a decrease in predictability (P < 0.00001) and an increase in nonlinearity (P = 0.00001) during the change from supine to standing posture. Decrease in MED, and increases in NL score and LLE in standing posture appear to be partly due to an increase in sympathetic activity of the autonomous nervous system in standing posture. An improvement in predictability during controlled breathing appears to be due to the introduction of a periodic component.

Adult↗
PubMed2003

Deficient coordination of associated postural adjustments during a lifting task in children with neurodevelopmental disorders.

Precision grip and concomitant anticipatory postural adjustments were investigated in 11 children (three females, eight males; mean age 9 years 1 month, SD 11 months) with attention-deficit-hyperactivity disorder (ADHD); 12 children (three females, nine males; mean age 9 years, SD 7 months) with developmental coordination disorder (DCD), and 13 children (two females, 11 males; mean age 9 years 9 months, SD 11 months) with a combination of ADHD and DCD (ADHD+). There were two comparison groups: an age-matched group (four females, 11 males; mean age 9 years 1 month, SD 14 months) and a younger age group (five females, six males; mean age 6 years 5 months, SD 8 months). Adaptation to different weights was evaluated by lifting a specialized grip instrument monitoring grip force, load force, and centre of foot pressure displacements. Children with ADHD+ showed: (1) excessive grip forces, (2) decreased amplitude and prolonged onset of postural adjustments, and (3) reduced ability to adapt the motor output. Children with ADHD and DCD did not scale manual and postural forces in amplitude and time domains. Children with DCD also differed in delayed timing of postural adjustments. Results indicate that children with ADHD and DCD show a spectrum of neural dysfunctions underlying poor motor coordination, which are not specific to the clinical disorder.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

Postural control during reaching in preterm children with cerebral palsy.

Postural control during reaching with the dominant arm was assessed in 58 preterm children with cerebral palsy (CP) aged 2 to 11 years, comprising 34 with spastic hemiplegia (17 males, 17 females) and 24 with bilateral spastic CP (bilateral CP; 15 male, 9 females). Assessments were made by multiple surface electromyogram (EMG) and kinematic recording. Mean gestational age at birth for the children with spastic hemiplegia and those with bilateral CP was 28.6 weeks (SEM 0.33) and 28.2 weeks (SEM 0.34) respectively; their mean birthweights were 1158 g (SEM 58) and 1190 g (SEM 59) respectively. All but one of the children with spastic hemiplegia could walk without restriction, the exception being a child who had self-mobility with limitations. In the group of children with bilateral CP, nine walked without assistive devices, 10 could walk with assistive devices, and five children needed a wheelchair for self-mobility. Comparison data of 29 typically developing children (10 males, 19 females) born at term with appropriate birthweight were available. Results indicated that in most children with CP the basic level of postural control ('direction-specificity', i.e. muscle activation on the side opposite to direction of body sway) was intact. However, the children with CP showed dysfunctions in: (1) recruitment order of the postural muscles, i.e. they exhibited a stereotyped top-down recruitment; and (2) the ability to modulate muscle contraction (that registers on EMG) to task-specific conditions. The latter dysfunction was more pronounced in children with bilateral CP than in those with spastic hemiplegia. Postural dysfunctions were correlated to some extent with the degree of disability in everyday activities as assessed by the Pediatric Evaluation of Disability Inventory.

Age Factors↗
PubMed1999

Development of postural adjustments during reaching in infants with CP.

The development of postural adjustments during reaching movements was longitudinally studied in seven infants with cerebral palsy (CP) between 4 and 18 months of age. Five infants developed spastic hemiplegia, one spastic tetraplegia, and one spastic tetraplegia with athetosis. Each assessment consisted of a simultaneous recording of video data and surface EMGs of arm, neck, trunk, and leg muscles during reaching in various lying and sitting positions. The basic organization of postural adjustments of the children developing spastic CP was intact. Their main problem was a deficient capacity to modulate the postural adjustments to task-specific constraints - a deficit which was attributed to a combination of an impaired motor coordination and deficits in sensory integration. The child with spastic-dyskinetic CP showed distinct abnormalities in the basic organization of postural adjustments.

Cerebral Palsy↗
PubMed2006

Role of patient posture during puncture on successful unilateral spinal anaesthesia in outpatient lower abdominal surgery.

BACKGROUND AND OBJECTIVE: Unilateral spinal anaesthesia is a useful anaesthesia technique in lower abdominal surgery, especially in an outpatient setting. Patient posture is pivotal in the achievement of unilateral anaesthesia. Nevertheless, no studies have elucidated the influence of patient posture during the anaesthetic injection on unilaterality. Thus, the aim was to compare the effect of patient posture, during the induction phase of spinal anaesthesia, on block characteristics. METHODS: Eighty patients, ASA I-II, scheduled for unilateral hernioplasty were randomized into two groups. Anaesthesia was performed in lateral position in Group 1 (G1) with operative side down and in sitting position in Group 2 (G2) whose patients were then immediately turned on their lateral side. All patients were maintained for 20 min in lateral position with their operative side down. Hyperbaric bupivacaine 1% 10 mg were used. RESULTS: Unilateral anaesthesia was seen in 80% (32/40) and 12.5% (5/40) of G1 and G2, respectively. The readiness for surgery was faster in G1 (P < 0.0001). The motor block in the non-operative side was stronger in G2 (P < 0.0001). The offset of sensory block was faster in G1 (P = 0.0001). The offset of motor block was slower in G1 (P = 0.0008). The time for voiding was shorter in G1, although not significant. CONCLUSIONS: Lateral posture during the induction of spinal anaesthesia is pivotal for a higher success of unilateral block, a fast readiness to surgery, and a fast recovery. Therefore, this technique can be considered feasible and time-saving for lower abdominal surgery.

Abdomen↗