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At least 757 records · Page 42Linked to original sources
PubMed2006

Influence of vision and static stretch of the calf muscles on postural sway during quiet standing.

The purpose of this experimental study was to evaluate the effects of vision and stretching of the calf muscles on postural sway during quiet standing. Under pre-stretch conditions, participants stood on a force plate for 30s and the sway of the ground reaction force center of pressure was recorded. The following postural sway variables were calculated off-line: sweep speed, sway speed, standard deviation, maximal mediolateral range, maximal anteroposterior range, mean mediolateral position and mean anteroposterior position. For post-stretch conditions, participants stood quietly on a device that was utilized to impose a static 3 min ankle joint dorsiflexion stretch. Immediately thereafter, participants moved onto the force platform where postural sway parameters were again recorded. Randomized eyes-open and eyes-closed conditions were tested in both cases. Results showed that postural sway significantly increased due to stretch (sweep speed, sway speed, standard deviation, maximal anteroposterior range, mean anteroposterior position), as well as eye closure (sweep speed, sway speed, standard deviation, maximal mediolateral range, maximal anteroposterior range). The interaction between stretch and eye closure was also significant (sweep speed, sway speed, standard deviation, maximal mediolateral range), suggesting that there were only minor increases in postural sway after stretch under the eyes-open condition. It was suggested that stretching of the calf muscles has the effect of increasing postural sway, although this effect can be greatly compensated for when vision is included.

Adult↗
PubMed2005

Optimization model predictions for postural coordination modes.

This paper examines the ability of the dynamic optimization model to predict changes between in-phase and anti-phase postural modes of coordination and to evaluate influence of two particular environmental and intentional constraints on postural strategy. The task studied was based on an experimental paradigm that consisted in tracking a target motion with the head. An original optimal procedure was developed for cyclic problems to calculate hip and ankle angular trajectories during postural sway with a minimum torque change criterion. Optimization results give a good description of the sudden bifurcation phase between in-phase and anti-phase postural coordination modes in visual target tracking. Transition frequency and predicted effects of environmental and intentional constraints are also in line with experimental observations described in existing literature. In particular, these investigations pointed out that postural planning process can be related to the minimization of a dynamic cost criterion with an equilibrium constraint. In conclusion, the optimization technique is well suited for the prediction of postural modes of coordination and seems to offer many opportunities for better comprehension of neuromuscular movement control.

Ankle↗
PubMedDate not supplied

Clinical implications from an exploratory study of postural management of breech presentation.

The results from an exploratory study of the effectiveness of maternal knee-chest posture for producing cephalic version of breech presentation are shown. Methods are briefly described and clinical implications are presented. Among 25 women, fewer who performed the maternal knee-chest postural intervention experienced fetal cephalic version than women in the control group who did nothing to influence breech presentation. Despite limitations of the underpowered findings, trends in the data may indicate that parity and gestational age were potentially relevant covariates of version. Postural management is not an evidence-based practice. This exploratory study indicates that maternal knee-chest posture may work opposite to the expected direction, but the small sample size precludes generalizations about efficacy of knee-chest postural management. At least one adequately powered trial that controls for parity and gestational age is needed to determine whether knee-chest postural management results in no effect, a small, or small to moderate clinically significant effect.

Apgar Score↗
PubMed2006

Quantitative analysis of the velocity and synchronicity of diaphragmatic motion: dynamic MRI in different postures.

The objectives of this study were to assess the relationship between right and left hemidiaphragmatic motions during breathing in normal subjects and to investigate alterations in lung motion with changes in posture, using dynamic magnetic resonance (MR) imaging. Imaging was conducted with a 1.5-T MR scanner using fast imaging employing steady-state acquisition with a torso coil. Eight healthy subjects were instructed to breathe from end-inspiration to end-expiration as slowly and as deeply as possible. Imaging and breathing were started together to afford sequential images on the coronal plane. Imaging sequences were performed in supine, prone, left lateral decubitus and right lateral decubitus postures. The component of movement of the most cephalic point in the cephalocaudal axis was measured, and the diaphragmatic excursion (maximum hemidiaphragmatic displacement), synchrony and velocity of the right and left hemidiaphragmatic motions were calculated during the expiratory phase and the inspiratory phase, respectively. Excursion was greater in the right hemidiaphragm in most postures, except the left lateral decubitus. In supine and prone postures, both hemidiaphragms moved synchronously in both inspiratory and expiratory phases. In both lateral decubitus postures, the hemidiaphragms moved asynchronously with different velocities in the expiratory phase but with the same velocities in the inspiratory phase. The method described here allowed the assessment of diaphragmatic motions. Motions in the right and left hemidiaphragms changed with posture. In addition, diaphragmatic motion differed between expiratory and inspiratory phases. This study suggests the further potential of dynamic MR imaging for the evaluation of pulmonary functions or deficiencies.

Adult↗
PubMed2005

Perceptual-motor organization of children's catching behaviour under different postural constraints.

The experiment investigates the perceptual-motor organization underlying children's catching performance when the demands on the postural system are varied. For this purpose, one-handed catching performance was observed under different postural constraints in children aged 9-10 years. Two groups of eleven participants, classified as either good or poor catchers, performed one-handed catches under three different postural conditions: standing, sitting, and standing while pressing a button positioned to a postural support aid (PSA). Results revealed, first, that when seated, poor catchers approached the level of the good catchers' performance. Second, poor catchers improved their performance by using the PSA, but not to the same performance as when sitting. Third, there was no effect of postural condition on the performance of the good catchers. The performance increase in the poor catchers is attributable to a combined change in functional postural sway and better timed movement of the catching hand, made possible by exploiting the extra surface support area afforded by sitting.

Biomechanical Phenomena↗
PubMed2006

Influence of posture and stimulus parameters on post-activation depression of the soleus H-reflex in individuals with chronic spinal cord injury.

In non-disabled (ND) individuals, reflexes are modulated by influences related to physiologic state (e.g., posture, joint position, load) and activation history. Repeated activation of the H-reflex results in post-activation depression (PAD) of the response amplitude. The modulation associated with physiologic state and activation history is suppressed or abolished in individuals with spinal cord injury (SCI). While posture is known to affect H-reflex amplitude and PAD in non-disabled individuals, the effect of posture on PAD in SCI individuals is not known. Further, while the amount of PAD is also known to be influenced by the stimulus rate and by the amplitude of the evoked reflex, the interaction of posture with stimulus parameters has not been previously investigated in either group. We investigated differences in PAD of the soleus H-reflex between SCI subjects and ND subjects during sitting versus supported standing. Subjects were tested using paired conditioning-test stimulus pulses of 2.5s and 5s interpulse intervals (ISI) and with stimulus intensity adjusted to evoke reflex responses of 20% and 40% of the maximum motor response. We found standing posture to be associated with significantly less PAD in SCI subjects compared to ND subjects. In both groups, shorter ISIs and smaller reflex amplitudes were associated with greater PAD of the H-reflex. These results indicate that postural influences on post-activation modulation, while present, are impaired in individuals with chronic incomplete SCI.

Adolescent↗
PubMed2006

Relationship of progression of visual field damage to postural changes in intraocular pressure in patients with normal-tension glaucoma.

PURPOSE: To evaluate whether postural changes of intraocular pressure (IOP) are associated with progression of visual field damage in patients with normal-tension glaucoma (NTG). DESIGN: Prospective, noncomparative, nonrandomized study. PARTICIPANTS: Sixty eyes of 33 patients with NTG. METHODS: Intraocular pressure, blood pressure (BP), and pulse rate (PR) were measured in both sitting and supine positions. Visual fields were examined using Humphrey Field Analyzer (HFA; Zeiss-Humphrey Instruments, Inc., San Leandro, CA). Changes in mean deviation (MD) per year (dB/year), that is, MD slope, were calculated by linear regression analysis of the HFA Statpac 2 program. MAIN OUTCOME MEASURES: The relationship between postural changes of IOP and MD slope was analyzed. The correlation between postural changes of IOP and cardiovascular parameters such as BP and PR also was analyzed. RESULTS: The IOP in the supine position was significantly higher than that in the sitting position (P<0.001, paired t test). There was no significant correlation between MD slope and sitting IOP (Pearson r = 0.172; P = 0.188), but a significant correlation was found between MD slope and supine IOP (r = -0.261; P = 0.043). The MD slope significantly correlated with IOP elevation caused by the postural change (r = -0.682; P<0.001). The systolic BP in the supine position correlated with postural changes of IOP (r = 0.364; P = 0.004), but other cardiovascular parameters did not correlate with IOP parameters. CONCLUSIONS: The progression of visual field damage in NTG is associated with IOP in the supine position and the magnitude of IOP elevation accompanying postural changes. These results suggest that deterioration in NTG may occur when patients are lying flat during sleep.

Aged↗
PubMed2006

Distance impairs postural stability only under binocular viewing.

Prior studies indicate that postural stability under binocular viewing is not better than under monocular viewing. This was tested at the distances of 145 cm [Fox, C.R. (1990). Some visual influences on human postural equilibrium: binocular versus monocular fixation. Perception and Psychophysics, 47 (5), 409-422] and 90 cm [Isotalo, E., Kapoula, Z., Feret, P.H., Gauchon, K., Zamfirescu, F., & Gagey, P.M. (2004). Monocular versus binocular vision in postural control. Auris Nasus Larynx, 31 (1), 11-17]. On the other hand, postural stability is known to decrease with distance increase. We re-examined the effect of binocular versus monocular viewing on postural stability at near and far distances (40 and 200 cm), and for both young (25.7+/-2.7 years), and old subjects (61.2+/-4.6 years). For both groups of subjects, proximity decreased the area of CoP, the standard deviation of antero-posterior sway (SDy) and the variance of speed. The group of elderly presented increased variance of speed at far distance in comparison with young subjects. The novel finding is the interaction between distance and viewing condition. Under binocular viewing, the area of CoP was significantly higher at far distance than at near; in contrast, monocular viewing produced similar CoP values at both distances. Increased instability at far distance when both eyes are viewing is attributed to decreased sensitivity to binocular disparity cues and to visual motion in depth resulting from body sway. Monocular viewing would provide similar stability at far and at near distance, because sensitivity to lateral visual motion, detected monocularly, decreases less with distance than sensitivity to binocularly detected motion in depth. Alternatively, such monocular viewing could increase subject's attention and lead to tighter postural control regardless of the distance.

Adult↗
PubMed2006

Postural effects when cycling in late pregnancy.

AIM: This study assessed if upright cycling is preferable to semi-recumbent cycling during pregnancy. METHOD: Healthy women with low risk singleton pregnancies were tested at 34-38 weeks gestation. They cycled for 12 min, either semi-recumbent (45 degrees, n = 27) or upright (n = 23), at 135-145 beats min(-1). RESULTS: When semi-recumbent, minute ventilation was greater (p<0.03) at rest and systolic blood pressure and pulse pressure were greater during exercise (p<0.05). Exercise maternal heart rate, oxygen consumption, oxygen consumption per kilogram, minute ventilation, cardiac output, stroke volume, mean and diastolic blood pressures and arterio-venous oxygen difference were posture-independent. All increased with exercise (p<0.01), except stroke volume when semi-recumbent (p>0.05). Small post-exercise fetal heart rate increases (by 8 beats min(-1), p<0.05) were similar in both postures (n = 11 in each sub-group), with no adverse changes. Fetal heart rate accelerations and uterine activity (n = 11 in each sub-group) were not influenced by posture or exercise. CONCLUSIONS: (1) Neither posture had a distinct advantage. (2) Both postures were safe for short duration cycling. (3) The same target maternal heart rates are suitable for both postures because they resulted in similar oxygen consumptions and fetal heart rates.

Bicycling↗
PubMed2002

A field comparison of neck and shoulder postures in symptomatic and asymptomatic office workers.

Poor neck and shoulder postures have been suggested to be a cause of neck and shoulder pain in computer workers. The present study aimed to evaluate and compare the head, neck and shoulder postures of office workers with and without symptoms in these regions, in their actual work environments. The two all female subject groups reported significantly different discomfort scores across five trials repeated in a single working day. The results of repeated video capture and two-dimensional motion analysis showed that there were trends for increased head tilt and neck flexion postures in the symptomatic subjects (n = 8), compared to the asymptomatic subjects (n = 8). Symptomatic subjects also tended to have more protracted acromions compared with asymptomatic subjects and showed greater movement excursions in the head segment and the acromion. All subjects demonstrated an approximately 10% increase in forward head posture from their relaxed sitting postures when working with the computer display, but there were no significant changes in posture as a result of time-at-work.

Adult↗
PubMed1997

A technique for recording and analysis of postural changes associated with thermal comfort.

The recording of posture has a long history in the study of ergonomics, but has generally been concerned with the assessment of mechanical strain on the human body. This paper extends the concern to the thermal implications of posture. A change in posture can change the effective body surface area available for heat exchange with the environment and therefore the metabolic rate per unit body surface area. This effect is systematised into a method of postural coding which reflects the extent of changes in effective body surface area available for heat exchange. The paper reports a brief assessment of the extent of the effect of posture in normal office work and the extent to which posture is temperature-related.

Body Surface Area↗
PubMed2000

Postural analysis of paramedics simulating frequently performed strenuous work tasks.

Paramedics who perform emergency rescue functions are highly susceptible to musculoskeletal injuries. Through an interview and survey process firefighters, many of whom are cross-trained paramedics in a consortium of 14 suburban fire departments, identified and rated tasks that were perceived to be both strenuous and frequently performed. The objective of the current study was to describe the working postures and the forces applied as firefighter/paramedics (FF/Ps) simulated specific roles within the following tasks identified by the survey: (1) transferring a patient from a bed to a stretcher using bedsheets, (2) transferring a patient from the ambulance stretcher to a hospital gurney, (3) carrying a victim down a set of stairs and around a landing using a stairchair, (4) carrying a victim down a set of stairs and around a landing using a backboard, and (5) carrying a victim down a set of stairs using a stretcher. Ten two-person teams of FF/Ps participated and were videotaped to obtain postural data for the upper and lower extremities as they performed each role in the simulated two-person tasks. Trunk postures were obtained using lumbar motion monitors. Static hand forces were estimated using a hand-held dynamometer at the most physically demanding points for each role within each task. The postural and force data were averaged across subjects performing identical roles to quantify the postures assumed by the FF/Ps at the most strenuous moments during task performance. Based on these analyses we concluded that: (1) when transferring victims from a bed to a stretcher the FF/P on the bed was able to maintain an upright and more stable posture by standing as opposed to kneeling, (2) an interface board should be used to reduce the frictional forces when transferring victims from a bed to a stretcher or from a stretcher to a gurney, thereby reducing the need to lift the victim with flexed torsos and/or shoulders, and (3) equipment and training that encourages the FF/P in the leader role to walk facing forward during victim transport, especially when descending stairs, potentially results in safer transit.

Allied Health Personnel↗
PubMed1996

Postural and symptomatic improvement after physiotherapy in patients with dizziness of suspected cervical origin.

OBJECTIVE: To assess postural performance in patients with dizziness of suspected cervical origin in whom extracervical causes had been excluded, and to assess the effects of physiotherapy on postural performance and subjective complaints of neck pain and dizziness. DESIGN: Prospective, randomized, controlled trial. SETTING: Primary care centers and a tertiary referral center. PATIENTS AND SUBJECTS: Of 65 referrals, 43 patients were excluded because extracervical etiology was suspected. Of the remaining 22 patients, 17 completed the study (15 women, 2 men, x age 37 yr, range 26-49). The controls were 17 healthy subjects (15 women, 2 men, x age 36 yr, range 25-55). INTERVENTION: Physiotherapy based on analysis of symptoms and findings, and aimed to reduce cervical discomfort. Patients were randomized either to receive immediate physiotherapy (n = 9), or to wait 2 months, undergo repeat measurements, and then receive physiotherapy (n = 8). MAIN OUTCOME MEASURES: Posturography, measuring velocity and variance of vibration-induced body sway and variance of galvanically induced body sway. Subjective intensity of neck pain (Visual Analog Scale ratings, 0-100), intensity and frequency of dizziness (subjective score 0-4). RESULTS: The patients manifested significantly poorer postural performance than did healthy subjects (.05 > p > .0001). Physiotherapy significantly reduced neck pain and intensity and the frequency of dizziness (p < .01), and significantly improved postural performance (.05 > p > .0007). CONCLUSIONS: Patients with dizziness of suspected cervical origin are characterized by impaired postural performance. Physiotherapy reduces neck pain and dizziness and improves postural performance. Neck disorders should be considered when assessing patients complaining of dizziness, but alternative diagnoses are common.

Adult↗
PubMed1996

The relationship of postural sway to sensorimotor function, functional performance, and disability in the elderly.

OBJECTIVE: To examine the relationship of postural sway to sensorimotor impairment, functional performance, and self-reported disability. DESIGN: Cross-sectional cohort. SETTING: Department of Veterans' Affairs Medical Center. PATIENTS: One hundred community-dwelling elderly unable to climb stairs step over step. MAIN OUTCOME MEASURES: Postural sway (area of ellipse and path length, eyes open and closed), sensorimotor (strength, sensation, range of motion, central processing time), functional performance (functional reach, timed gait, mobility skills, endurance), and disability (MOS-SF36, Falls Efficacy Scale [FES]). RESULTS: Postural sway area measures correlated with sensorimotor measures: (1) During eyes-closed conditions, increased sway occurs in individuals with sensory deficits (p < .05); (2) Sway was positively correlated with tibialis anterior latency (p < .05); (3) Sway area measures increased with increased strength (p < .05). The sway/strength relationship may be explained by week subjects improving their stability by limiting rather than increasing sway. Sway was not significantly correlated with any measures of physical performance. Sway was correlated with some measures of disability: (1) Eyes-closed measures of postural sway were correlated with FES scores (p < .05); (2) Sway was not correlated with the MOS-36 physical functioning question. When controlling for functional measures, eyes-closed measures of sway significantly predicted FES scores (p < .03). CONCLUSIONS: Measures of postural sway are more likely capturing sensorimotor deficits rather than differentiating functional performance abilities, and the relationship between postural sway and self-reported disability is inconsistent.

Activities of Daily Living↗
PubMed2002

Anticipatory postural adjustments under simple and choice reaction time conditions.

Two different schemes of the central organization of anticipatory postural adjustments (APAs) have been proposed: one of them assumes that postural and focal components of an action are results of a single control process (single-process hypothesis) while the other one suggests that these two components result from two relatively independent control processes (dual-process hypothesis). To distinguish between the two hypotheses, we investigated changes in the relative timing of the postural and focal components under self-paced, simple reaction time (SRT) and choice reaction conditions (CRT). Standing subjects performed one of four small arm movements resulting in a standard postural perturbation (dropping a load). APAs were quantified as changes in the background muscle activity as well as shifts of the center of pressure. APAs occurred at a larger delay prior to the focal movement under the self-paced condition than under the SRT condition. Under the CRT condition, actual RTs were longer than under SRT, but APAs were more similar to those under self-paced conditions. A negative correlation between the reaction time and APA onset was found. The findings demonstrate that the focal and APA components of an action can be decoupled, thus supporting the dual-process hypothesis. Changes in APAs with action suggest a possibility of modifications of a function that transforms two parallel control signals into a single command to the focal and postural muscles, based on postural requirements and behavioral constraints.

Adult↗
PubMed1985

Holding postures characteristic of unstable bladder.

Holding postures to resist uninhibited detrusor contractions are illustrated and discussed. These postures were observed in children with urodynamically proved unstable bladders. The majority of the holding postures involved compressing the urethral meatus or the perineum in girls, or contracting all of the skeletal muscles or squeezing the glans penis in boys. The holding posture required the child to remain still. Younger children used straightforward holding postures, while older children adopted more sophisticated and less recognizable positions. These clinical observations seem to suggest that a physician should probably suspect an unstable bladder in any child who often demonstrates any of these postures.

Adolescent↗
PubMed2004

[Postural control in idiopathic scoliosis: comparison between healthy and scoliotic subjects].

PURPOSE OF THE STUDY: To assess the effects of idiopathic scoliosis on undisturbed postural control in young female teenagers. MATERIAL AND METHODS: The centre of pressure (CP) displacements, measured through a force platform, were decomposed into two elementary components in order to differentiate the net postural performance, as revealed by the horizontal motions of the centre of gravity (CGh) and the level of muscular activity expressed by the vertical difference CP-CGv. The CG horizontal displacements were estimated from those of the CP with a low pass filter taking into account the subjects' anthropometry. Fifteen healthy teenagers and fifteen teenagers with idiopathic scoliosis were asked to stand still upright for three successive trials of 64s, rest periods of similar duration being allowed between each trial. RESULTS: The results indicate differences in the postural control between the two populations: scoliotic CG motions are more important than those of healthy subjects. In the medio-lateral direction, the CGh motions can be primarily explained by the concomitant increase observed at the CP-CGv level. To be more precise, one should have in mind that the CP-CGv amplitudes determine the horizontal acceleration communicated to CGh. On the other hand, despite significative increases of the CP-CGv in the antero-posterior direction, the CGh motions appear to be unaffected by these initial conditions. This feature suggests that appropriate control mechanisms can intervene in this antero-posterior direction for the scoliotic group whereas a similar organization cannot be observed in the medio-lateral direction. DISCUSSION: The differences observed in the postural performance for the healthy and scoliotic groups can be explained in various ways. The capacity of the scoliotic group to counteract huge CP-CGv motions may be linked to the location of the postural muscles involved in this control: the triceps surae for the antero-posterior direction, and the abductor-adductor hip muscles for the medio-lateral one. Only the action of the latter group can be indeed perturbed by the specific constraints occurring at the hip level and resulting from the scoliosis. On the other hand, the general increase of the CP-CGv motions, by expressing an overwhelming muscular activity in the whole set of postural muscles, does suggest that the drive of the descending motor commands is largely modulated and is likely the consequence of a central disfunctionning.

Adolescent↗
PubMed2004

Why and how are posture and movement coordinated?

In most motor acts, posture and movement must be coordinated in order to achieve the goal of the task. The focus of this chapter is on why and how this coordination takes place. First, the nature of posture is discussed. Two of its general functions are recognized; an antigravity role, and a role in interfacing the body with its environment such that perception and action can ensue. Next addressed is how posture is controlled centrally. Two models are presented and evaluated; a genetic and a hierarchical one. The latter has two levels; internal representation and execution. Finally, we consider how central control processes might achieve an effective coordination between posture and movement. Is a single central control process responsible for both movement and its associated posture? Alternatively, is there a dual coordinated control system: one for movement, and the other for posture? We provide evidence for the latter, in the form of a biomechanical analysis that features the use of eigenmovement approach.

Central Nervous System↗