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At least 1,081 records · Page 60Linked to original sources
PubMed2006

Postural equilibrium during pregnancy: decreased stability with an increased reliance on visual cues.

OBJECTIVE: The purpose of this study was to determine whether there are changes in postural equilibrium during pregnancy and to examine whether the incidence of falls increases during pregnancy. STUDY DESIGN: Static postural balance measures were collected from 12 pregnant women at 11 to 14, 19 to 22, and 36 to 39 weeks gestation and at 6 to 8 weeks after delivery and from 12 nulligravid control subjects who were matched for age, height, weight, and body mass index. Subjects were asked to stand quietly on a stable force platform for 30 seconds with eyes open and closed. Path length and average radial displacement were computed on the basis of the average of 3 trials for each condition. The women were asked at each session if they had sustained a fall in the previous 3 months. RESULTS: Postural stability remained relatively stable during the first trimester; however, second and third trimester and postpartum values for path length and average radial displacement with eyes open and closed were increased significantly compared with the control subjects, which indicates diminished postural balance. The difference between the eyes open and closed values of path length increased as pregnancy progressed. Although 25% of pregnant women sustained falls, none of the control subjects had fallen in the past year. CONCLUSION: These data suggest that postural stability declines during pregnancy and remains diminished at 6 to 8 weeks after delivery. The study also indicates that there is an increased reliance on visual cues to maintain balance during pregnancy.

Accidental Falls↗
PubMed2005

[Towards a better understanding and quantitative assessment of pushing, a postural behaviour caused by some strokes].

INTRODUCTION: Postural control aims to build up and align the body orientation (posture) and stabilize body segments. The existence of two separate mechanisms, one for the control of body orientation with respect to gravity and one for its stabilisation, is an emerging concept that allows a better understanding of postural disorders, including pushing, after stroke. Objectives. - Literature review concerning pushing, one of the most puzzling postural behaviours after stroke. METHODS: Critical review of papers indexed in Medline and book chapters dealing with pushing. RESULTS: There is no agreement about the definition of pushing: some authors consider that pushers push himself toward the paretic side using the healthy arm or leg; others consider that pushers lean (list) toward the side opposite the lesion and resist any attempt to become more upright. Surprisingly, the push itself has never been measured. Some ordinal scales have been recently proposed, but their psychometric properties have not been analysed. These methodological insufficiencies explain in part the disagreements about frequency (from 5% to 50% of patients with stroke) and cause(s) of pushing. CONCLUSION: Pushing may be the most dramatic clinical manifestations of an extreme bias in the construction of the biological vertical. We argue for a better assessment of vertical perception/representation after stroke involving the three modalities of the biological (subjective) vertical: the visual vertical, the haptic or tactile vertical, and especially the postural vertical.

Functional Laterality↗
PubMed2005

[Immediate effects of physiotherapy session of lower limb by balneotherapy on postural control].

OBJECTIVE: The aim of this study was to compare the immediate effects of standard physiotherapy (S) and balneotherapy (B) on the postural capacity of subjects with lower-limb injuries. METHODS: The postural sway of 12 voluntary subjects was evaluated before (REF1 and REF2) and after two different physiotherapy sessions performed in the swimming pool (B) or under (S). The centre of pressure (CP) trajectory was recorded by use of a force platform. CP displacements in the mediolateral and anteroposterior axes were then separated into two elementary superimposed components: the horizontal motion of the centre of gravity (CG) and the difference between the CP and the vertical projection of the CG (CP-CG). The amplitude of the latter component (CP-CG) is thought to express neuromuscular activity. All trajectories were then analysed in terms of classical and frequency parameters. RESULTS: Postural sway did not differ before and after the physiotherapy sessions. Following both sessions, the mean CG velocity decreased significantly (P<0.5). The area of CP-CG trajectory was diminished solely by the aquatic exercise (P<0.5) and was associated with decreased amplitude of motion along the anteroposterior axis (P<0.05), which suggests decreased neuromuscular activity to maintain posture. CONCLUSION: Interestingly, decreased motion was observed along the anteroposterior axis, which corresponds to ankle movements. Exercising lower-limb muscles under water could reinforce proprioceptive input, resulting in a better postural control.

Adolescent↗
PubMed2004

Classroom posture and self-reported back and neck pain in schoolchildren.

The study reported here aims to identify the extent of back pain experienced by 11-14 year old schoolchildren, and establish the intensity, duration and frequency of exposure to physical risk factors present in schools. This paper considers the sitting postures of schoolchildren in the classroom. The sitting postures of 66 children were recorded in normal lessons using the Portable Ergonomic Observation Method (PEO). The study found significant associations between flexed postures and low back pain. Static postures and neck and upper back pain were also associated. This study has implications for schools, designers and people in the field of work related musculoskeletal disorders. Further research is required to examine the association between sitting posture and pain reported at different spinal locations.

Adolescent↗
PubMed2006

The effect of six keyboard designs on wrist and forearm postures.

There is increasing evidence that alternative geometry keyboards may prevent or reduce arm pain or disorders, and presumably the mechanism is by reducing awkward arm postures. However, the effect of alternative keyboards, especially the new designs, on wrist and arm postures are not well known. In this laboratory study, the wrist and forearm postures of 100 subjects were measured with a motion analysis system while they typed on 6 different keyboard configurations. There were significant differences in wrist extension, ulnar deviation, and forearm pronation between keyboards. When considering all 6 wrists and forearm postures together, the keyboard with an opening angle of 12 degrees , a gable angle of 14 degrees , and a slope of 0 degrees appears to provide the most neutral posture among the keyboards tested. Subjects most preferred this keyboard or a similar keyboard with a gable angle of 8 degrees and they least preferred the keyboard on a conventional laptop computer. These findings may assist in recommendations regarding the selection of keyboards for computer usage.

Adult↗
PubMed2004

Effect of lower-extremity muscle fatigue on postural control.

OBJECTIVE: To examine the effects of fatigue of the lower extremity on postural control during single-leg stance. DESIGN: Pretest-posttest. SETTING: University research laboratory. PARTICIPANTS: Fourteen healthy volunteers (age, 21+/-2y) with no history of lower-extremity injury or neurologic deficits. INTERVENTIONS: Testing consisted of isokinetically fatiguing the sagittal plane movers of the ankle, knee, or hip with measures of static postural control. Postural control was assessed with three 30-second trials during unilateral stance with eyes open. MAIN OUTCOME MEASURES: Center of pressure excursion velocity (COPV) in the frontal and sagittal planes. RESULTS: Fatigue at the knee and hip led to postural control impairment in the frontal plane, whereas fatigue at the ankle did not. In the sagittal plane, fatigue at all 3 joints contributed to postural control impairment. CONCLUSIONS: Our results suggest that there is an effect of localized fatigue of the sagittal plane movers of the lower extremity on COPV. It appears that fatigue about the hip and knee had a greater adverse affect on COPV.

Adult↗
PubMed2004

Effects of vision and arm position on amplitude of arm postural tremor in patients with multiple sclerosis.

OBJECTIVES: To quantify the effects of vision and arm position on arm postural tremor, comparisons were made between flexed and extended arm positions performed with the eyes open and closed. DESIGN: Case-control study. SETTING: National multiple sclerosis (MS) center in Belgium. PARTICIPANTS: Sixteen patients (32 arms) with MS who had intention tremor and 16 healthy controls (32 arms). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The amplitude of postural tremor was assessed by a magnetic position sensor attached to the index finger. RESULTS: The amplitude of postural tremor was not influenced by changes in visual condition or different arm positions. Both healthy controls and MS patients made more directional changes in the flexed, compared with the extended arm position. CONCLUSIONS: The amplitude of the arm postural tremor in MS is independent of vision and arm position. Selecting 1 arm position is sufficient to assess postural tremor amplitude.

Arm↗
PubMed2005

Nonlinear and chaos characteristics of heart period time series: healthy aging and postural change.

In this study we investigated nonlinear and linear characteristics of heart period variability with aging in supine and standing posture. Sixty healthy subjects (8-61 years) divided in three age groups participated in the study. Heart period variability was assessed by measurement of short-term scaling exponent, sample entropy, largest Lyapunov exponent and spectral low-frequency and high-frequency power. In standing, there was significant increase in short-term scaling exponent and largest Lyapunov exponent in all subjects, and significant decrease in sample entropy in children (<15 years) and young adults (15-39 years). Increasing age is associated with reduction in sample entropy in supine posture. Mutual effect of aging and postural change was reflected on heart rate and sample entropy. Correlation between low-frequency-to-high-frequency power ratio and short-term scaling exponent was found in supine posture. In standing both low-frequency and high-frequency powers are correlated with short-term scaling exponent and sample entropy. These results show that posture, standing compared to supine, has significant effect on nonlinear properties of heart period variability in healthy subjects while the influence of healthy aging is less pronounced. The findings indicate that intrinsic properties of heart period dynamics, reflected on nonlinear measures, are altered only by robust changes of autonomic modulation of heart rate.

Adolescent↗
PubMed2005

Sagittal plane moment arms of the female lumbar region rectus abdominis in an upright neutral torso posture.

BACKGROUND: Prior imaging studies of torso muscle moment arms for use as inputs into biomechanical models have been derived from subjects lying supine. Recent research suggests moment arms of the rectus abdominis are larger when standing versus lying supine. METHODS: Axial MRI images, through and parallel to the intervertebral discs were obtained from five females in a standing upright neutral posture. Digitizing software was utilized to quantify the distance in the sagittal plane between the centroids of the intervertebral disc and the rectus abdominis muscle, and converted to the transverse plane to allow comparisons with studies with subjects in a supine posture. FINDINGS: The mean sagittal plane moment arms in the transverse plane were 9.7, 9.1, 8.5, 8.5 and 9.8 cm at the L(1)/L(2), L(2)/L(3), L(3)/L(4), L(4)/L(5) and L(5)/S(1) intervertebral levels, respectively. Compared with a study on females of a similar age group, the moment arms from this study were larger at each level, increasing from 7.3% larger at L(1)/L(2) to 43.7% larger at L(5)/S(1). INTERPRETATION: Accurate anatomical geometrical representation in biomechanical models is necessary for valid estimates of internal loading. Sagittal plane rectus abdominis moment arms were larger from the upright neutral torso posture in this study compared to studies with subjects lying supine. This suggests the torso internal moment generating capability would be represented differently in biomechanical models that use data from studies where subjects were upright, which is more reflective of the postures biomechanical models are utilized for, than when using anatomical geometry derived from supine postures.

Abdomen↗
PubMed2005

Independent control of voluntary movements and associated anticipatory postural responses in a bimanual task.

OBJECTIVE: When one hand loads the other arm, EMG responses in the stationary arm anticipate the load. This study used transcranial magnetic stimulation over each hemisphere to clarify the relationship between a voluntary movement on one side and the anticipatory postural response on the other. METHODS: Subjects (n = 7) performed elbow flexion movements of one arm as a reaction-time task. Because subjects' arms were linked, flexion about one elbow resulted in extension force about the other, and an anticipatory response occurred in those elbow flexor muscles. After the 'go' signal and before the predicted onset of EMG, transcranial magnetic stimuli were delivered over one or other motor cortex. RESULTS: Stimulation contralateral to the reaction-time movement delayed the onset of voluntary EMG (46 ms in right biceps, 77 ms left) but did not alter the onset of EMG in the postural arm. Stimulation contralateral to the anticipatory postural response delayed only the postural EMG (left 96 ms, right 52 ms). CONCLUSIONS: Thus, the associated voluntary and postural responses were delayed independently by stimuli over their respective contralateral motor cortex. SIGNIFICANCE: This suggests that, although timing of responses may be linked by an initial signal, the response from each motor cortex develops independently.

Adult↗
PubMed2004

Impaired postural control in patients affected by tension-type headache.

Sixteen subjects, affected by chronic tension-type headache (TTH) accordingly to the International Headache Society Classification (1988) criteria, in presence of tenderness in pericranial muscles,with a mean age of 37+/-11.8 years, and ten healthy volunteer subjects, age and sex matched, were submitted to postural analysis by Static Posturography (S.Ve.P. Amplaid). Aim of the study was to evaluate whether patients with TTH have disturbed postural control, as compared to normal subjects. Postural analysis considered all posturographic variables but focused on spectral frequency analysis of body sway. In both open (OE) and closed eyes (CE) condition, spectral frequency analysis showed a significantly increased body sway at low (OE= p < or = 0.01; CE= p < or = 0.01) and middle (OE= p < or = 0.01; CE= p < or = 0.01) frequencies on the antero-posterior (y) plane and at low frequencies (OE= p < or = 0.05; CE= p < or = 0.05) on the lateral (x) plane. Statistical analysis was performed using the Student's t test for unpaired data, p value 0.05 defined significant. The proprioceptive input seems to be predominant at middle and high frequencies in maintaining posture, our results seem then to suggest a proprioceptive disturbance in TTH patients. The disturbance is likely related to chronic pericranial muscle contraction and tenderness. Posturography and spectral analysis may help not only in the diagnosis of a postural disturbance but even more in the follow-up of TTH patients, during and after a medical and/or a rehabilitative treatment.

Adult↗
PubMed2005

Postural activity of the abdominal muscles varies between regions of these muscles and between body positions.

The abdominal muscles have an important role in control and movement of the lumbar spine and pelvis. Given there is new evidence of morphological and functional differences between distinct anatomical regions of the abdominal muscles, this study investigated whether there are regional differences in postural activity of these muscles and whether recruitment varies between different body positions. Eleven subjects with no history of low back pain that affected function or for which they sought treatment participated in the study. Electromyographic (EMG) activity of the upper, middle and lower regions of transversus abdominis (TrA), the middle and lower regions of obliquus internus abdominis (OI) and the middle region of obliquus externus abdominis (OE) was recorded using intramuscular electrodes. All subjects performed rapid, unilateral shoulder flexion in standing and six subjects also moved their upper limb in sitting. There were regional differences in the postural responses of TrA with limb movement. Notably, the onset of EMG of the upper region was later than that of the lower and middle regions. There were no differences in the EMG onsets of lower and middle TrA or OI. The postural responses of the abdominal muscles were also found to differ between body positions, with recruitment delayed in sitting compared to standing. This study showed that there is regional differentiation in TrA activity with challenges to postural control and that body position influences the postural responses of the abdominal muscles. These results may reflect variation in the contribution of abdominal muscle regions to stability of the trunk.

Abdominal Muscles↗
PubMed2005

Changes in coordination of postural control during dynamic stance in chronic low back pain patients.

The human postural system operates on the basis of integrated information from three independent sources: vestibular, visual and somatosensory. It is conceivable that a derangement of any of these systems will influence the overall output of the postural system. The peripheral proprioceptive system or the central processing of proprioceptive information may be altered in chronic low back pain (CLBP). We therefore investigated whether patients with CLBP exhibited an altered postural control during quiet standing. Dynamic posturography was performed by 12 CLBP patients and 12 age-matched controls. Subject's task was to stand quietly on a computer-controlled movable platform under six sensory conditions that altered the available visual and proprioceptive information. While the control of balance was comparable between the two groups across stabilized support surface conditions (1-3), CLBP patients oscillated much more than controls in the anterior-posterior (AP) direction in platform sway-referenced conditions (4-6). Control experiments ruled out that increased sway was due to pain interference. In CLBP patients, postural stability under challenging conditions is maintained by an increased sway in AP direction. This change in postural strategy may underlie a dysfunction of the peripheral proprioceptive system or the central integration of proprioceptive information.

Adaptation, Physiological↗
PubMed2004

Epidemiology of musculoskeletal disorders among computer users: lesson learned from the role of posture and keyboard use.

Reports in the scientific literature and lay press have suggested that computer users are at increased risk of upper extremity musculoskeletal disorders (MSDs). Early studies often found elevated rates of MSD outcomes among keyboard users when compared to non-users. Attention soon focused on specific aspects of keyboard work that might be responsible for the observed rate increase. In this review, the epidemiological evidence examining associations between MSD outcomes and computer user posture and keyboard use intensity (hours of computer use per day or per week) are examined. Results of epidemiological studies of posture and MSD outcomes have not been entirely consistent. Reasons for the inconsistency in results include cross-sectional study design (with possible failure to assure that measured exposure preceded health effect), imprecision of posture measures used, and difficulties involved in analyzing multiple related variables. Despite the inconsistencies, it appears from the literature that posture is an independent risk factor of modest magnitude for MSDs among computer users. It appears that lowering the height of the keyboard to or below the height of the elbow and resting the arms on the desk surface or chair armrests is associated with reduced risk of neck and shoulder MSDs. Results of epidemiological studies examining computer use (hours keying per day or per week) are more consistent than those examining posture, although some inconsistency is observed. Reasons for the inconsistency include possible selective survival bias resulting from cross-sectional study design, differences in exposure categorization, and possible interaction with other exposure variables. Overall, the literature shows that daily or weekly hours of computer use is more consistently associated with hand and arm MSDs than with neck and shoulder MSDs.

Computers↗
PubMed2005

Myofascial trigger point development from visual and postural stressors during computer work.

The mechanism of musculoskeletal pain underlying low level static exertions, such as those experienced during computer work, is poorly understood. It was hypothesized that static postural and visual stress experienced during computer work might contribute to trigger point development in the trapezius muscles, resulting in myofascial pain. A study was conducted to observe the development of myofascial trigger points while 16 female subjects used a computer under conditions of high and low postural and visual stress. Trigger point development was monitored via expert opinion, subject self-report, and electromyographic activity. Only the high visual stress conditions resulted in greater trigger point sensitivity as reported by subjects and the myofascial specialist. Cyclic trends in median frequency of the EMG signal were assessed for the trapezius muscle. When high visual stress was combined with low postural stress condition there were significantly fewer cycles (1.6 cycles) as compared to the condition of low visual and low postural stress (2.8 cycles), and the condition of high visual and high postural stress (3.5 cycles). These significant differences between conditions were found for the right trapezius but not for the left. The findings suggest that high visual stress may be involved in the development of the myofascial pain response.

Adult↗
PubMed2005

Influence of cranio-cervical posture on three-dimensional motion of the cervical spine.

Although a consistent pattern of ipsilateral movement coupling between cervical spine rotation and lateral flexion has been widely described, variability in these movement patterns has not been reported. In 30 asymptomatic subjects, the ranges of primary and coupled movements were determined in the neutral posture, and in the extremes of cervical spine protraction and retraction. All measurements were performed using the SpinT three-dimensional goniometer for which excellent intra-tester reliability was demonstrated for both primary (ICC(3,1) 0.93-0.98) and coupled (ICC(3,1) 0.76-0.98) movements. The ranges of primary and coupled movements changed significantly when movement was initiated from the end-range postures (P < 0.001). In the neutral posture, approximately 70% of subjects demonstrated an ipsilateral pattern of coupled movement. During cervical rotation, the dominant coupling pattern seen in neutral was no longer retained in retraction, while the protracted posture had a greater influence on the coupled movements accompanying primary lateral flexion. The concept of a stereotypical pattern of cervical spine movement coupling is not supported by these results. The posture in which movements are initiated appears to have a significant influence on the three-dimensional kinematics of the cervical spine.

Adult↗
PubMed2004

Cortico-muscular coupling in a patient with postural myoclonus.

We investigated the cortico-muscular coherence in a patient with posturally induced cortically originating negative myoclonus. We recorded simultaneously 50 channels EEG and EMG from quadriceps and biceps femoris muscles of the left upper leg. Three experimental conditions were investigated with the patient in a seated position: (i) recording during rest (Rest), (ii) recording while the patient had to hold his left leg horizontally stretched out (Postural), and (iii) recording while the patient had to hold his left leg horizontally stretched out against a vertical force (Postural against force). Coherence, phase difference and cumulant density were computed as indicators for cortico-muscular coupling. The cortical component preceding the silent period was shown by averaging and was reconstructed. During postural and postural against force conditions, the EEG over the vertex was significantly coherent with EMG, in alpha (7-15 Hz) and beta range (15-30 Hz). The strongest coherence peak was at 21 Hz. No high-frequency coherence was observed. The phase difference and the cumulant density estimate corresponded to a 32 ms time lag between motor cortex and muscles, with EEG leading. The broadening of the coherence spectrum at which the motor cortex drives the muscles together with the excessive coherence levels and the giant SEP could reflect the hyperexcitability of the sensorimotor cortex. The frequency content of the coherence may be characteristic for this type of myoclonus. The results lend support to the view that the frequency analysis may have some diagnostic potential in cortical myoclonus.

Aged↗
PubMed2005

Alteration of posture-related cortical potentials in mild traumatic brain injury.

This paper presents additional evidence showing the persistent functional deficits in concussed athletes as revealed by altered movement-related cortical potentials (MRCP) preceding whole body postural movements at least 30 days post-injury. Eight student-athletes participated in this study (a) prior to injury; and (b) 3, 10 and 30 days after MTBI. EEG was recorded while subjects produced static balance tasks and dynamic postural movements. All subjects were cleared for sport participation within 10 days post-injury based upon neurological and neuropsychological assessments as well as upon clinical symptoms resolution. There was a persistent reduction of MRCP amplitude prior to initiation of postural movement up to 30 days post-injury, although abnormal postural responses basically recovered within 10 days post-injury. The frontal lobe MRCP effects were larger than posterior areas. This supports the notion that behavioral symptoms resolution may not be indicative of brain injury resolution. Overall, persistent alteration of movement-related cortical potentials after MTBI may indicate residual disturbance of neuronal networks involved in preparation and execution of postural movements and a lower threshold for brain re/injury.

Adolescent↗