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At least 595 records · Page 33Linked to original sources

PubMed1994

The differential effects of external ankle support on postural control.

Ankle supports are commonly used in an attempt to decrease the risk of ankle injury during sport. However, their use may also impair postural control, which is an integral component of sports participation. The aim of this study was to investigate the effects of three different ankle supports (tape, brace, and elastic bandage) on postural control in 24 normal subjects with a mean age of 24.8 years (+/- 4.4). Two measures were used to evaluate postural control in one-legged stance with the eyes closed: variability of mediolateral ground reaction force (acquired from a force platform) and frequency of foot touchdowns by the nonsupport leg (assumed to indicate ability of the subject to maintain one-legged stance posture). Both measures revealed a differential effect for ankle support on postural control. The use of an elastic bandage had no significant effect on postural control (p > 0.05), while the use of tape or a brace had a significant detrimental effect (p < 0.05). While wearing the tape or a brace, subjects were less steady and touched down more frequently. Restriction of ankle movement was offered as a possible explanation for the results, since postural control was impaired only by the ankle supports which limited ankle motion. These findings may have implications regarding impaired athletic performance.

Adult↗

PubMed1996

Effect of orthotics on postural sway following inversion ankle sprain.

Orthotic devices have been shown to successfully modify selected aspects of lower extremity mechanics and enhance foot stability during the support phase of running. It was hypothesized that orthotic intervention would relieve excessive strain on the ankle ligaments and reduce postural sway, especially in subjects with acute ankle sprains. The primary purpose of this study was to determine if orthotics would reduce postural sway in injured and uninjured subjects. Thirteen subjects with acute inversion ankle sprain and 12 uninjured subjects were assessed for postural sway on the Balance System under two treatment conditions (orthotic and nonorthotic) and four platform movements. A three-factor repeated measures analysis of variance revealed a significant group X treatment interaction, suggesting that postural sway with orthotic intervention improved significantly more in injured subjects than in uninjured subjects. A significant platform movement X treatment interaction, furthermore, revealed that postural sway for the four movement conditions was dependent upon treatment (orthotic vs. no orthotic). Tukey post hoc analysis revealed that orthotic intervention significantly reduced postural sway when the platform moved in the medial/lateral plane and inversion/eversion plane. This research suggests that custom-fit orthotics may restrict undesirable motion at the foot and ankle and enhance joint mechanoreceptors to detect perturbations and provide structural support for detecting and controlling postural sway in ankle-injured subjects.

Acute Disease↗

PubMed1991

[Relationship between postural support and intentional movement: biomechanical approach].

The presentation is in two parts. The first, more theoretical, section reviews the basic biomechanical features underlying the movement of all bodies, both animate and inanimate, being in contact with the ground. Application of biomechanical laws shows that intentional movement can only be executed if the external environment can react to the movement of members relative to the body. Thus, it is theoretically necessary that the part of the body, including the body segment(s) that are located between the ones which are voluntarily moved and the supporting surfaces, ie, the "postural support", is involved in the motor activity. The general equilibrium conditions of a complex mechanical system such as the human body are then examined to show why movement itself disturbs balance stability and that postural reactions are, a priori, required to preserve this stability. The second sections includes an analysis of postural activities for several types of sensory-motor tasks. They are shown to be synergistically organized, and the major features of this organisation are described. The anticipatory postural adjustments (APA) which occur BEFORE the start of voluntary movement, and are thus "preprogrammed", are then examined. It is shown that they depend on the parameters of the planned movement, posture and the uncertainty about the tasks. This is followed by a discussion of the reasons why APA may be considered as a counter-perturbation, opposing, in advance the perturbation of equilibrium brought about by the voluntary movement. The presentation concludes with several hypotheses for explaining the organisation of postural activity associated with voluntary movement. The most likely appears to be a process of "parallel" command of the voluntary and postural components.

Biomechanical Phenomena↗

PubMed1991

Volumetric comparison of seated and standing test postures.

Published protocols for the volumetric assessment of upper-extremity edema differ regarding patients' posture. The present study was designed to determine the effect of posture on test-retest reliability and mean volume. Thirty women were tested in both seated and standing postures. For the dominant hand, test-retest reliabilities for the seated posture were identical to those for the standing posture. Test-retest reliability was slightly stronger for the nondominant hand in sitting than for the same hand in standing. Both postures afforded clinically acceptable test-retest reliabilities. The mean volumes in sitting were significantly lower than those in standing (p less than .0001), thus suggesting that volumetric measures should be considered discontinuous if the patient's test posture is altered. Mean volumes of the dominant hand averaged 9.3 ml more than those of the nondominant hand. It is suggested that this discrepancy be considered in the establishment of goals for edema control and in the determination of the need for continued edema treatment.

Adolescent↗

PubMed1995

The effect of environmental regulations on postural control after stroke.

OBJECTIVES: The primary objective of this study was to examine the effect of environmental predictability on postural control after stroke. A reaching task for seated subjects was used as the postural perturbation. Trajectory stability (the pathway followed by the subject's body center for pressure with respect to time during the reaching task) was used as the index of postural control. It was hypothesized that trajectory stability would be greater under predictable conditions. METHOD: A specially designed electromechanical system was used to measure the trajectory stability ratios for 100 subjects, 50 with poststroke hemiplegia and 50 who had not had stroke. All subjects completed a task that required reaching to the left versus reaching to the right, under predictable versus unpredictable conditions. Postural control was measured via a trajectory instability ratio in both the anterior-posterior and medial-lateral planes. RESULTS: Although the effect of predictability on postural control was significant, it was not as hypothesized for both groups. There was greater trajectory stability under unpredictable conditions when reaching to the right as measured in both the anterior-posterior and medial-lateral planes and when reaching to the left as measured in the medial-lateral plane. CONCLUSION: These findings refute the assumption of the hierarchical, predictable-to-unpredictable-environment model for postural control evaluation and treatment. The relationship between information processing demands and postural skill is probably more complex than the simple linear association implied. Perhaps the two conditions, predictable and unpredictable, should be worked on concurrently, not sequentially.

Adult↗

PubMed2001

A novel approach for evaluating level, frequency and duration of lumbar posture simultaneously during work.

OBJECTIVES: Electrogoniometers are used to collect continuous information on postural distributions among workers. Enormous quantities of data are generated that have to be reduced to meaningful parameters (angle, frequency, and duration). In this study we propose statistical models to determine these essential characteristics of postural load on nurses, housekeepers, and office workers. METHODS: A direct registration of the lumbar posture was made over a workday with an inclinometer. An exposure variation analysis was used to summarize information on the angle of trunk flexion, the time period of maintained postures, and the percentage of worktime in a data matrix. A hierarchical regression analysis was used to compare these characteristics among nurses (N=64), housekeepers (N=16), and office workers (N=27). RESULTS: The occupational groups did not differ for either frequency or duration of trunk flexion over 30 degrees since frequency and duration were inversely related. Nurses experienced longer worktimes than the office workers did for trunk flexion between 30 and 70 degrees maintained <5 seconds, whereas office workers experienced longer worktimes in smaller angles (< 30 degrees) for longer periods. Comparable differences in the distributions of postural load were found between housekeepers and office workers. CONCLUSIONS: This study describes the use of hierarchical models in analyses of the exposure level, frequency, and duration of postural load simultaneously and offers an alternative to conventional ergonomic analysis in which the dynamics of exposure are often ignored. The distinction in postural load between nurses or housekeepers and office workers is best determined by the combination of trunk angle and time period.

Biomechanical Phenomena↗

PubMedDate not supplied

Effect of foot posture and inverted foot orthoses on hallux dorsiflexion.

A pronated foot posture is considered to be a factor in limitation of dorsiflexion at the first metatarsophalangeal joint during weightbearing. Customized foot orthoses are widely used to increase dorsiflexion at the first metatarsophalangeal joint in people with pronated feet. However, the effect of foot posture and customized foot orthoses on maximum first metatarsophalangeal joint dorsiflexion has not been widely investigated. This study sought to determine 1) the relationship between foot posture and static maximum first metatarsophalangeal joint dorsiflexion and 2) the effect of customized foot orthoses on static maximum first metatarsophalangeal joint dorsiflexion in people with pronated feet. Foot posture was assessed using the Foot Posture Index. Static maximum first metatarsophalangeal joint dorsiflexion of the right foot was determined using a goniometer while participants stood relaxed with and without Blake-style inverted (30 degrees) foot orthoses positioned under their feet. There was a significant negative correlation between Foot Posture Index and static maximum first metatarsophalangeal joint dorsiflexion (r = -0.587). Inverted (30 degrees) foot orthoses increased the magnitude of static maximum first metatarsophalangeal joint dorsiflexion from 83.4 degrees to 85.3 degrees in participants with an excessively pronated foot posture. However, this difference was not statistically significant. People with pronated feet are more likely to exhibit limitation of dorsiflexion at the first metatarsophalangeal joint during gait, and inverted foot orthoses are unlikely to be effective in increasing dorsiflexion at the first metatarsophalangeal joint in these people.

Adult↗

PubMed1999

Cardiovascular control and plasma catecholamines during rest and mental stress: effects of posture.

In order to understand the complex autonomic adjustments that occur during the psychological challenges of normal daily life, autonomic responses to psychological stress were studied by evaluating the effects of body posture on various indices of sympathetic and parasympathetic regulation during performance of a psychological task. Twelve male subjects were studied in various postures (supine, sitting and standing), and during performance of the Colour Word Test (CWT) when sitting and then when standing. This procedure was subsequently repeated in reverse order (first standing and then sitting) after 15 min of supine rest. Blood samples for assay of plasma catecholamines were obtained before and during each CWT. Spectral analysis of beat-to-beat variations of heart rate (HR) and blood pressure (BP) was applied in order to obtain non-invasive indices of sympathetic and parasympathetic regulation. HR, diastolic BP, mid-frequency band power (0.07-0.14 Hz) of HR and systolic BP, and plasma adrenaline and noradrenaline concentrations showed significant increases when changing from supine to sitting to standing posture, whereas high-frequency band power (0.15-0.50 Hz) of HR decreased in a posture-dependent fashion. In the sitting position, the CWT caused significant increases in HR, BP and plasma adrenaline levels, and decreased HR and BP variability indices. In the standing posture, the CWT responses differed significantly from those during sitting for HR (a mild decrease during standing), high-frequency band power of HR (decreased more while sitting), high-frequency band power of BP (decreased more while standing), and plasma adrenaline responses (larger during sitting). Posture-related differential effects were observed on indices of sympatho-adrenomedullary activation during performance of a psychological challenge, whereas indices of parasympathetic activity indicated primarily less vagolytic effects when the task was performed in the standing posture. Our findings therefore underline the complexity of the adjustments that occur in neurohumoral and haemodynamic parameters during the psychological challenges of daily life.

Adult↗

PubMed1999

Postural synergies associated with a stepping task.

BACKGROUND AND PURPOSE: Synergistic relationships among multiple muscle components are thought to exist to simplify control of posture and movement. The purpose of this study was to examine the extent to which children, young adults, and older adults exhibit consistent sequences of postural muscle activation when lifting the right foot onto a step from a standing position. SUBJECTS: Twenty subjects without known impairments of the neuromuscular system (10 male, 10 female) in each of 3 age groups--children (8-12 years), young adults (25-35 years), and older adults (65-73 years)--participated. METHODS: A pressure switch taped to the subject's right foot was used to determine movement onset and offset. Latencies of muscle activation were determined using surface electromyography. A preferred postural synergy was defined as the sequence of postural muscle activation observed during the majority of trials for each subject. RESULTS: Mean movement times did not differ among age groups. Although the left tibialis anterior (TA) muscle was the first of the postural muscles activated in 93% of the trials, subjects displayed considerable variability in the subsequent order of postural muscle activation. Across subjects, a total of 14 different preferred postural synergies were observed. Age groups did not differ in the number of different synergies. CONCLUSION AND DISCUSSION: Early TA activation may reflect biomechanical constraints of the stepping task, producing forward displacement of the center of mass over the changing base of support. The fact that subjects of all ages were quite variable in the specific sequences of muscles activated subsequent to the TA suggests that, for this type of task, therapists should not focus their interventions on facilitating execution of particular synergy patterns.

Adolescent↗

PubMed1999

Antiorthostatic posture as an earth model of the effect of microgravity on the human body.

We examined the horizontal and vertical component of diagonal optokinetic nystagmus (DOKN) in sitting posture and in the last 15 minutes of antiorthostatic posture at -30 degrees lasting 3 hours. The antiorthostatic posture is suited to the earthy model of the fluid shifting observed in microgravity. We found that the frequency of the vertical component of DOKN is rarer in antiorthostatic posture than in sitting posture. Moreover, the amplitude of the vertical component of DOKN is lower in antiorthostatic posture than is the amplitude of the horizontal component. According to our examinations, we suppose that the frequency and amplitude of vertical OKN are directed by different cerebral structures. Furthermore, we found that the heart rate becomes slower and the diastolic pressure is augmented after antiorthostatic posture and visual stimulation.

Adult↗

PubMed2000

[Age and constitutional features in the forming of posture in children 7 to 14 years of age].

Longitudinal study of forming of the posture was performed in 138 healthy pupils of Moscow school No. 710 aged from 6.5 to 14 of both sexes. Simultaneously children were examined anthropometrically and their constitution was determined after Schtefko. The posture was examined visually. It was established that posture forms within observation terms depending on sex, age and somatotype. Peak age for the risk of posture disturbance is 9-11 for girls and 10-12 for boys. Digestive and muscular somatotypes provide favourable prognosis respective to posture (in girls), while astenoid somatotype is the worst. Special type of posture defect is characteristic for each somatotype. In children with digestive and muscular somatotype primary posture defects disappear by 12-14. In children with astenoid and thoracal somatotype their number, in contrary, grows.

Adolescent↗

PubMed2000

Unique postural control of upside-down swimming catfish, Synodontis nigriventris, not affected by the change of gravity.

In general, most fishes maintain a swimming posture with the dorsal side towards the water surface under normal gravity condition. In contrast to normal fishes, a catfish Synodontis nigriventris, shows a unique postural control. The catfish keeps its posture with the ventral side towards the water surface and the dorsal side towards water bottom under normal gravity. This evidence leads one to assume that the upside-down posture of the catfish is controlled by gravity sensation in a manner different from that of other fishes. However, it has remained unclear to date whether the gravity sensation contributes to the unique postural control of this catfish. We examined its postural control in intact and labyrinth-removed catfish using a clinostat which generates a specific gravity environment (pseudo-microgravity) on earth. In addition, we examined its postural control under microgravity during parabolic flights.

Animals↗

PubMed2003

Activity of different classes of neurons of the motor cortex during postural corrections.

The dorsal side-up body orientation in quadrupeds is maintained by a postural system that is driven by sensory feedback signals. The spinal cord, brainstem, and cerebellum play essential roles in postural control, whereas the role of the forebrain is unclear. In the present study we investigated whether the motor cortex is involved in maintenance of the dorsal side-up body orientation. We recorded activity of neurons in the motor cortex in awake rabbits while animals maintained balance on a platform periodically tilting in the frontal plane. The tilts evoked postural corrections, i.e., extension of the limbs on the side moving down and flexion on the opposite side. Because of these limb movements, rabbits maintained body orientation close to the dorsal side up. Four classes of efferent neurons were studied: descending corticofugal neurons of layer V (CF5s), those of layer VI (CF6s), corticocortical neurons with ipsilateral projection (CCIs), and those with contralateral projection (CCCs). One class of inhibitory interneurons [suspected inhibitory neurons (SINs)] was also investigated. CF5 neurons and SINs were strongly active during postural corrections. In most of these neurons, a clear-cut modulation of discharge in the rhythm of tilting was observed. This finding suggests that the motor cortex is involved in postural control. In contrast to CF5 neurons, other classes of efferent neurons (CCI, CCC, CF6) were much less active during postural corrections. This suggests that corticocortical interactions, both within a hemisphere (mediated by CCIs) and between hemispheres (mediated by CCCs), as well as corticothalamic interactions via CF6 neurons are not essential for motor coordination during postural corrections.

Action Potentials↗

PubMed2003

Changes in heart rate and R-wave amplitude with posture.

BACKGROUND: Effect of gravity on heart rate and blood pressure are well documented but the effect of posture on R-wave amplitude has not been studied. AIM: To investigate the effect of posture on the heart rate (HR) and R-wave amplitude (RWA). METHODS: The electrocardiograph (ECG) was recorded in 20 young subjects on two occasions. A 5 minute recording of resting ECG was taken with the subject adopting the following postural cycle: lying, sitting, standing, sitting and lying positions. RESULTS: The standing HR was significantly higher than that in sitting and lying positions, but the RWA was significantly lower in standing compared to the sitting and lying postures. The HR significantly increased at the initial phase of postural changes, irrespective of the position. For example, the HR increased from lying to sitting (66.6+/-2.3 to 85.0+/-10.9 beat x min(-1)) but also increased when changed from sitting to lying (70.6+/-10.6 to 85.2+/-8.7 beat x min(-1)). CONCLUSION: Body posture has an effect on HR and RWA. The changes are probably related to orthostatic haemodynamic stress as well as changes in cardiac electrical axis. Whether the cause of the initial increase in the HR during postural change was attributed to skeletal muscle reflex or venous return requires further investigation.

Adult↗

PubMed2003

Lumbar posture--should it, and can it, be modified? A study of passive tissue stiffness and lumbar position during activities of daily living.

BACKGROUND AND PURPOSE: Physical therapists commonly attempt to reduce and prevent low back pain by "improving" individuals' lumbar posture. To investigate the physical therapy clinical practice of attempting to "improve" lumbar posture, measures of passive tissue stiffness and angular deformation during activities of daily living were used. PARTICIPANTS: The lumbar spine posture of 150 university students was measured as the inclinometer angle difference between L1 and S1. Eighteen female participants (6 with hypolordosis, 6 with hyperlordosis, and 6 controls without lumbar spine impairment) were recruited from this lumbar posture database. Hypolordosis and hyperlordosis were clinically classified by physical therapists. METHODS: Lumbar passive tissue stiffness was measured during sitting, standing, and walking before and after a 12-week exercise program, and estimates of lumbar passive tissue strain were calculated from those measurements. RESULTS: The neutral zone (NZ), a range of lumbar positions of low passive tissue stiffness, was identified. Prior to training, the subjects with hypolordosis had more passive tissue strain during sitting than the subjects with hyperlordosis, and the subjects with hyperlordosis stood in extension relative to their NZs while the control subjects and subjects with hypolordosis stood within their NZs. Before and after training, subjects in all 3 groups walked with lumbar spine positions within their NZs. After training, the lumbar posture of the subjects with hypolordosis and the subjects with hyperlordosis changed toward a "mean" (mid-range) lumbar posture. After the exercise program, subjects in all 3 groups stood and walked with their lumbar spines in positions within their NZs, and they sat with their lumbar spines flexed relative to their NZs. DISCUSSION AND CONCLUSION: Knowing that tissue failure can be related to passive tissue strain, the results of this study support the clinical practice of attempting to change individuals' posture-related lumbar spine positions during activities of daily living. Lumbar passive tissue strain, as estimated from the NZ and angular deformation during activities of daily living, can be decreased, but can also be increased, by an exercise program.

Activities of Daily Living↗

PubMed2004

[Voluntary postural control learning with a use of visual bio-feedback in patients with spinocerebellar degenerations].

The study aimed at evaluation of possibility and features of voluntary postural control learning using biofeedback from a force platform in patients with spinocerebellar ataxias. Thirty-seven patients with different forms of spinocerebellar degenerations and 13 age-matched healthy subjects were trained to shift the center of pressure (CP) during several stabilographic computer games which tested an ability to learn 2 different types of voluntary postural control: general strategy and precise coordination of CP shifting. Despite the disturbances of static posture and ability for voluntary control of CP position, patients with spinocerebellar degenerations can learn to control a vertical posture using biofeedback on stabilogram. In contrast to healthy subjects, improvement of coordination in the training process does not exert a significant influence on the static posture characteristics, in particular on lateral CP oscillations. The results obtained suggest involvement of the cerebellum in both types of postural control that distinguishes them from pathology caused by motor cortex and nigro-striatal system involved only in one type of postural control.

Adolescent↗

PubMed2004

Effect of magnification lenses on student operator posture.

A distinct body of literature supports the association between clinical postures of the dental practitioner and work-related musculoskeletal disorders (WRMD). Several aids or devices have been tested to improve clinical posture in the interest of decreasing WRMD. The use of magnification lenses while performing dental procedures may increase the quality of work and decrease the likelihood of musculoskeletal problems. To date, only anecdotal and personal opinions had existed regarding the benefits of using magnification lenses, and no empirical evidence had authenticated the contention that use of magnification lenses exerts a positive change in operator posture. The objective of this study was to assess the effect magnification lenses had on the posture of dental hygiene students. Using a randomized crossover design, researchers videotaped nineteen senior dental hygiene students performing an intra-oral procedure with and without the use of magnification lenses. The tapes were then evaluated by a panel of five dental hygiene educators calibrated in the use of Branson's Posture Assessment Instrument (PAI). Results of a paired t-test indicate that the posture of the students while wearing magnification lenses was more acceptable (p=.019) than when wearing traditional safety glasses. Results of this study indicate a quantifiable change in acceptability of posture for clinicians wearing magnification lenses and suggest that the use of such lenses in dental education may be warranted.

Cross-Over Studies↗

PubMed1992

Influence of posture and prolonged head-down tilt on cardiovascular reflexes.

We investigated the influence of ten days 6 degrees head-down tilt (HDT) on short-term cardiovascular control. To help differentiate between the effects of HDT-induced fluid redistribution and changed autonomic cardiovascular modulation under prolonged HDT, the effect of acute posture changes was investigated as well. Six healthy male volunteers were studied. Continuous finger blood pressure was measured non-invasively by means of Finapres. Heart rate (HR) was derived from the electrocardiogram. Responses to forced breathing (FRSA), Valsalva's manoeuvre (VM), Mental Stress (MS) and Sustained Handgrip (SHG) were measured. Changing posture from HDT to standing enhanced the BP and HR responses to VM, both during straining and after release. During prolonged HDT, responses to VM changed toward the pattern seen in the upright posture before HDT, suggesting a strong influence of fluid redistribution. Neither posture nor prolonged HDT influenced HR variation during FRSA and responses to MS and SHG. BP variation during FRSA was influenced by posture but not by prolonged HDT. Thus, cardiovascular reflex tests which reflect the parasympathetic (FRSA) or the sympathetic (MS and SHG) efferents to the heart were not influenced by posture or prolonged HDT. Only the responses to VM were affected by both posture and prolonged HDT. These results are probably due to a decrease in blood volume and stroke volume under prolonged HDT, an increase in venous distensibility and, to a lesser extent, to inadequate cardiovascular regulatory responses.

Adult↗