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PubMed1981

Resistance to nasal airflow related to changes in head posture.

The relationship] between mode of respiration, cranial posture, and craniofacial morphology has been the subject of many articles in recent years. Some authors postulate that mouth breathers extend their heads backward in an effort to increase airway patency. The purpose of the present study was to determine whether artificially induced extended head posture decreases the resistance to nasal airflow. The experimental sample comprised fifteen male students with normal vertical facial proportions and no histories of chronic mouth breathing. In the sample, head posture was assessed by measuring the craniovertical angle by means of an angle finder. Nasal resistance units were calculated from the parameters of nasal airflow and differential pressure across the nasal airway during the complete respiratory cycle using an equation analogous to Ohm's law. Readings were obtained in both the normal and 10-degree extended head posture position, and the results were compared. No association could be found between an extended head posture position and a decreased resistance to nasal airflow.

Adult↗
PubMed1991

Analysis and improvement of work postures in the building industry: application of the computerised OWAS method.

Awkward work posture is associated with the development of musculo-skeletal disorders. Previous workplace investigations in new building construction have shown that physical work affects workers' health in 46% of jobs. There is, however, a need for detailed analysis of jobs having physical workload and ergonomics problems. OWAS (Ovako Working Posture Analysing System) is a simple observation method for postural analysis, but there has been no study of its use in the building construction industry. The work described here examined (a) the use of the OWAS method to analyse work postures in building construction, (b) the development of a portable computer system for the OWAS method, (c) improvement of work postures identified as poor, and (d) use of the results as part of the ergonomics training programme of the company. Suggestions for work redesign measures are given.

Journal Article↗
PubMed1994

Low-back disorders in agricultural tractor drivers exposed to whole-body vibration and postural stress.

The occurrence of low-back pain (LBP) was investigated in a population of 1155 tractor drivers exposed to whole-body vibration (WBV) and postural stress (response rate 91.2%) and in a control group of 220 office workers (response rate 92.2%). The subjects were questioned about several types of low-back symptom (LBP, sciatic pain, acute LBP, transient and chronic LBP) and various work- and individual-related risk factors, by using a standardized questionnaire. Vibration measurements were performed on a representative sample of the vehicles driven by the tractor drivers in the last ten years. Vibration magnitude and duration of exposure were used to calculate a vibration dose for each tractor driver. Perceived postural load was assessed in terms of frequency and/or duration of awkward postures at work. The prevalence of LBP was found to be greater in the tractor drivers than in the controls. After controlling for potential confounders by logistic modelling, low-back disorders were found to be significantly associated with both vibration dose and postural load. Back accidents and age were also significant predictors for LBP. Quantitative regression analysis indicated that vibration exposure and postural load were independent contributors to the increased risk for LBP according to a multiplicative model. The exposure levels for WBV recently recommended by a proposal of European Directive on physical agents seem to be more adequate to prevent long-term health effects on the lower back than the exposure limits suggested by the International Standard ISO 2631/1.

Journal Article↗
PubMed1995

Reduction of farmers' postural load during occupationally oriented medical rehabilitation.

Farmers' back problems may be associated with the amount of back flexion and the handling of heavy loads. The aim of this study was to analyse the effects of occupationally oriented medical rehabilitation courses on female farmers' postural load. Twenty seven female farmers (aged from 32 to 52 years) took part in four rehabilitation courses at one rehabilitation centre in Finland. The subjects suffered from various musculoskeletal symptoms, which decreased their work ability. The rehabilitation courses included two periods: the first lasted for 3 weeks and the latter for 1 week, organized 6 months after the first period. The work postures and their load on the musculoskeletal system were classified by the computerized OWAS method in three daily work phases. During the 3-week periods new work techniques were learned, and simultaneous bent and twisted postures for the back decreased from 34 to 4% of all studied work postures. Similarly, postures with one or both arms above shoulder level were reduced from 44 to 24%. Rechecking after the 6-month period confirmed that the adoption of new work techniques was consistent. The study showed that female farmers could change their work techniques during this kind of intensive rehabilitation period, and the changes were seen 6 months later in the follow-up.

Journal Article↗
PubMed1996

The reliability of postural sway measures using the 3SPACE Tracker.

OBJECTIVE: To investigate the reliability of three-dimensional postural control sway measures, in a normal population, using an electromagnetic device. DESIGN: A repeated measures design was used within and between sessions. BACKGROUND: Electromagnetic measurement has been proposed as a method of measuring postural sway; however, reliability within a normal population has not been shown. METHOD: An electromagnetic device, the 3SPACE Tracker, measured postural sway at the pelvis using sway path length and displacements in the anterior-posterior, medial-lateral and vertical direction. Ten subjects performed a postural control task involving two trials for six different sensory conditions, on two separate occasions, two weeks apart. RESULTS: The reliability of the technique was demonstrated by the repeatability of results for individual subjects within and between sessions. Individual subjects and sensory conditions were discriminated. Sway path length was the most consistent of the measures used. CONCLUSIONS: Three dimensional measures of postural sway are reliable and discriminatory in a normal population.

Journal Article↗
PubMed1996

Passive properties of the forearm musculature with reference to hand and finger postures.

OBJECTIVE: To quantify individual forearm muscle passive forces and evaluate their impact on hand function. DESIGN: The passive force-length properties of the 24 extrinsic hand and wrist muscles were determined in five fresh frozen cadaver arms. BACKGROUND: Muscle force production is a summation of the active and passive force components. The passive properties of the extrinsic finger musculature and wrist musculature appear to strongly affect both hand posture and hand movement. METHODS: The passive force-length properties of extrinsic hand and wrist muscles were determined by applying a slow, continuous extension to each muscle and recording the resulting tension. Each force-length curve was fit using exponential regression and were related to specific joint rotations and seven hand postures by calculating the muscle excursions for those postures. RESULTS: The exponential passive force-length relationship explained over 97% of the experimental variance. The largest passive forces were elicited in the digital extensors in grips involving large flexion angles such as tip pinch, key pinch, and a briefcase grip. CONCLUSIONS: The passive properties of the extrinsic finger musculature and wrist musculature affect both hand posture and movement especially in postures with flexed wrist and fingers.

Journal Article↗
PubMed2006

[Attentional control of postural stability in institutionalised elderly people: effects of a physical exercise program].

OBJECTIVE: We aimed to examine the effect of a physical activity program on postural sway and on the attentional control of postural abilities in elderly frail adults. METHOD: Twelve older adults (age 81.4+/-9 years) institutionalised in a geriatric care institution participated in the physical activity program posture-balance-mobility (PBM) twice a week (1 hour per session) for 12 weeks. We analysed stabilometric data for surface and length of the center of pressure (COP) sway, with eyes open and eyes closed, under single-task and dual-task conditions on a firm floor before and after the training program. During the static postural evaluation and under the dual-task condition, subjects performed an attention-demanding cognitive task, the random number generation task. RESULTS: Only the length of COP sway was more important under the dual-task condition than under the single-task condition (p=0.05). At baseline, cognitive performance was significantly weaker under the dual-task condition (standing) than under the single-task condition (seated), with eyes closed but not eyes open (p<0.05). However, after the training program, the performance of the cognitive task did not significantly differ between the dual-task condition with eyes closed and the single-task condition with eyes closed. CONCLUSION: The training program allowed elderly subjects to improve their ability to perform an attention-demanding cognitive task while standing still, in particular with their eyes closed. Although balance seemed to be less stable under the dual-task condition than under the single-task condition, these results could be interpreted as an improvement of the attentional control of postural stability.

Aged, 80 and over↗
PubMed1999

Mandibular posture during sleep in patients with obstructive sleep apnoea.

Vertical mandibular posture is thought to be related to narrowing of the upper airway, because mouth opening is associated with an inferior-posterior movement of the mandible and the tongue which influences pharyngeal airway patency. To test whether the mandibular posture is related to the occurrence and/or termination of obstructive sleep apnoea (OSA), the vertical mandibular position was recorded intraorally using a magnet sensor during a standard sleep study in seven patients with OSA. Measurements were recorded during sleep both in the supine and lateral recumbent positions. The percentage of total sleep time spent with mandibular opening greater than 5 mm was significantly larger (p<0.001) in patients with OSA (69.3+/-23.3%) compared with our previous results obtained from healthy adults without OSA (11.1+/-11.6%). The stage of sleep affected the vertical mandibular posture during sleep in the supine position, but not in the lateral recumbent position in patients with OSA. In non-rapid eye-movement sleep, mandibular opening increased progressively during apnoeic episodes and decreased at the termination of apnoeic episodes. In contrast, no significant change in mandibular posture occurred in apnoeic episodes during rapid eye-movement sleep. It was concluded that the vertical mandibular posture is more open during sleep in patients with OSA than in healthy adults and that mandibular opening increases progressively during apnoeic episodes and decreases at the termination of those episodes.

Analysis of Variance↗
PubMed1997

An investigation of poor cervical resting posture.

In an attempt to measure cervical resting posture, a device was developed to quantify the excursion of anatomical points on the upper and lower cervical spine. Measurements were taken from 427 randomly chosen subjects who had never sustained an injury to the neck or back. Excursion measurements were in good agreement over a month interval. Poor cervical resting posture was described by dividing the excursion angle data at each anatomical point into quintiles, and designating the first and fifth quintiles as extreme. Subjects whose upper and lower aspects of the cervical spine excursed by extremely small angles, and subjects whose upper and lower aspects of the cervical spine excursed by extremely large angles, were considered to have poor posture. These postures were markedly different. The study highlighted the need for further research into influences on habitual cervical resting posture.

Journal Article↗
PubMed1997

Postural sway and stepping response among working population: reproducibility, long-term stability, and associations with symptoms of the low back.

OBJECTIVE: To investigate the day-to-day reproducibility and long-term (9 months) stability of variables of postural control, and the associations of these variables with low-back and lower-extremity pain in a working population. DESIGN: Test-retest measurements of 18 healthy subjects. Cross-sectional study of 165 working women and 343 men. BACKGROUND: Sudden loss of postural balance may result in microtraumas of back structures. Therefore workers with decreased postural control may run an increased risk of low-back pain. There are few reports describing the reproducibility of force-plate-based posturography. METHODS: Amplitude and velocity of postural sway were measured with a force-plate in a two-feet stance with eyes open and closed, and in a one-foot stance with eyes open. A stepping response test was developed to measure the dynamic components of balance. RESULTS: The mean differences between the repeated measurements were generally 5-10% and the standard deviations of these differences were up to a quarter or one third of the mean measurement values. Sway velocity showed the best overall reproducibility. Men had a larger sway than women independent of age and anthropometry. The group of non-symptomatic subjects showed wide variation and a slightly lower sway than the groups with low-back or lower-extremity pain. CONCLUSIONS: Postural sway has moderate stability, wide variation, and slight associations with low-back symptoms in a working population.

Journal Article↗
PubMed1998

Effects of a lumbar support on spine posture and motion assessed by electrogoniometer and continuous recording.

OBJECTIVE: To determine whether belt wearing causes changes in lumbar posture and motion during standing and work-related activities. DESIGN: The lumbar spine sagittal kinematics of healthy subjects were assessed with an electrogoniometer during a dynamic test and continuous recording with and without a lumbar support. Correlation between data from electrogoniometer and X-ray was established in preliminary experiments. BACKGROUND: The effects of a lumbar support were previously investigated in few patients using radiological or invasive techniques under laboratory conditions, with special regard to the restriction of global motion in flexion and extension. Whether lumbar posture may also be involved during belt wearing remains unclear. There is also no evidence that these changes affecting lumbar motion and posture persist during prolonged activities. METHODS: The correlation between electrogoniometer and radiographic data was assessed in 12 subjects. Lumbar curve angles were evaluated in 15 healthy subjects, with and without one type of lumbar support, during standing in orthostatic, fully-flexed and fully-extended positions and during work-related activities with a portable computer. Lumbar motion parameters were flexion, extension and total range of motion. Lumbar posture parameters were lumbar curve angle in orthostatic position and mean lumbar curve angle during continuous recording. RESULTS: Electrogoniometric and radiographic data from lumbar curve angles and motion changes during flexion/extension of the spine were slightly different but reasonably well correlated (r = 0.58-0.77). The lumbar support decreased the mean total range of motion of the lumbar spine during a single flexion/extension movement by 17% and during continuous recording by 22%. The lumbar curve angle in the orthostatic position was reduced by 3 degrees and the mean lumbar curve (assessed by continuous recording) was reduced by 4 degrees (mean for 15 subjects). There were major individual changes in these two parameters and the reduction in lumbar curvature was correlated with the initial (r = 0.66-0.72). CONCLUSION: Electrogoniometer data on lumbar motion are reasonably well correlated with X-ray data. The comparative values registered during flexion/extension tests and continuous recording confirm that a support belt limits slightly global lumbar motion. As changes affecting postural parameters (orthostatic or mean values during continuous recording) depend on subject morphometry, individual parameters should be taken in account when evaluating and using a lumbar support.

Journal Article↗
PubMedDate not supplied

Postural stability and neurobehavioural effects of heat exhaustion among adult men.

The medical complications of heat disorders, including haematological, cardiovascular and renal damage, have been well documented. However, very little has been written on its neurological complications. The objective of this study was to assess the effects of heat exhaustion on postural stability and neurobehavioral functions of men. The study is prospective in design and spans a 3-year period. All soldiers who were diagnosed to have heat exhaustion (cases) from 1 March 1998 to 31 August 1998 were included in the study. For each case, a healthy soldier (matched for age, ethnicity, years of education and military vocation) was recruited to serve as control. Each subject had a neurobehavioral assessment by using the Swedish Performance Evaluation System (SPES), a computerized test battery. The postural stability of the subjects was assessed using a computerized postural sway system. Findings for 37 heat exhaustion cases and 37 controls revealed that cases had a significantly higher prevalence of neurasthenia symptoms compared to the controls. There were significant (small) differences between the cases and controls in the neurobehavioral tests of choice reaction time, digit span and some parts of colour word stress and logical series measures. Postural stability in the cases was significantly poorer when in the "eyes-closed" condition, compared with the controls. Men with heat exhaustion, studied 2 weeks after the acute episode, had significantly more symptoms of neurasthenia, poorer performance in short-term memory and slower reaction time. The cases (as a group) had significantly poorer postural stability.

Adult↗
PubMed1998

Postural responses to vibration of neck muscles in patients with uni- and bilateral vestibular loss.

Postural responses to vibration applied unilaterally to the dorsal neck muscles were recorded with a sway platform in 11 patients with bilateral vestibular loss (BLD), 13 patients with unilateral vestibular lesions (ULD) and 19 normal subjects. In the normals, the vibration induced a forward postural deviation. Vibration failed to induce postural sway in the BLD patients but induced a backwards head movement in 7 patients. In the ULD patients, vibration contralateral to the lesion induced normal forward sway, whereas ipsilateral vibration resulted in sway directed to the side of the lesion and backwards. The findings demonstrate the importance of concurrent vestibular signals in determining the behavioural response to neck afferent input. We propose that in normal subjects the intact vestibular signal gives no confirmation that a head movement has occurred so it is assumed that the lower body has tilted forwards which provokes a compensatory sway. In the total absence of vestibular function the neck signal may represent a real head movement so the preferential response is a head tilt to restore upright posture. The vestibular imbalance in the ULD patients is roughly equivalent to the asymmetrical signals obtained in a normal subject during head rotation to the intact side. The stretch signal induced by ipsi-lesional vibration confirms possible head rotation, thus provoking a compensatory postural sway. Copyright 1998 Elsevier Science B.V. All rights reserved

Journal Article↗
PubMed1997

Association of lip posture and the dimensions of the tonsils and sagittal airway with facial morphology.

The specific contribution of enlarged tonsils or adenoids to craniofacial growth remains unknown, and there is no agreement in the literature as to the significance of lip posture. This study assessed the separate associations of lip posture, sagittal airway size, and tonsil size with selected cephalometric measures. Clinical and cephalometric data of 207 children who presented for evaluation of tonsil and/or adenoid problems were evaluated. Multiple linear regression was used to assess the linear relationship between each of the three parameters and the cephalometric dependent variables. Open lip posture, reduced sagittal airway, and large tonsils were each associated statistically with a characteristic but different skeletal configuration. This association was proportional. Specifically, a more open lip posture was associated with a more backwardly rotated face and larger lower facial height. Reduced sagittal airway size was associated with en bloc backward relocation of the maxilla and mandible. Because the sella-nasion dimension shortened proportionally, the SNA and SNB angles were not affected. Larger tonsils were associated with more forward relocation and rotation of the maxilla and mandible and increased SNA and SNB angles. Because each of the three parameters was associated proportionally with a different craniofacial morphology, it is concluded that lip posture, sagittal airway size, and tonsil size represent three different and unrelated phenomena with respect to their effects on craniofacial growth and form.

Adolescent↗
PubMed1993

Control of Equilibrium Position and Stiffness Through Postural Modules.

If muscles are viewed as spring-like torque generators, then the integral of torque with respect to joint angle is the potential energy of that muscle. An energy function for the musculoskeletal system can be defined by summing the energy contribution of each muscle and the potential energy stored in the limb. Any local minimum in this energy landscape is a possible equilibrium position for the limb. The gradient of this function with respect to joint angles is a torque field, and the task of postural control is to find a set of muscle activations to produce a desired field. We consider one technique by which this approximation may be achieved: A postural module is defined as a synergy of muscles that produce a class of torque functions that converge at a constant equilibrium position, but whose stiffness at this position varies as a function of activation of the postural module. For a single-joint system, we show that through control of two such modules it is possible to produce any stiffness at any desired equilibrium position. To extend this scheme to a multijoint system, we initially derive the mechanical constraints on the shape of the restoring force field when a multijoint limb is displaced from equilibrium. Next, we consider voluntary control of the force field when the human arm is displaced from equilibrium: Mussa-Ivaldi, Hogan, and Bizzi (1985) have suggested that subjects are unable to voluntarily change the shape and orientation of the field, although they can readily scale it. This suggests existence of a limitation on the independent recruitment of arm muscles. We show, through simulation, that the inability to voluntarily control the shape and orientation of the restoring force field can be attributed to an organization of postural modules that act as local stiffness controllers. We propose that through coactivation, postural modules coarsely encode the work space and serve as an intermediate control system in the motor control hierarchy.

Journal Article↗
PubMed2001

A model of movement coordinates in the motor cortex: posture-dependent changes in the gain and direction of single cell tuning curves.

This article outlines a methodology for investigating the coordinate systems by which movement variables are encoded in the firing rates of individual motor cortical neurons. Recent neurophysiological experiments have probed the issue of underlying coordinates by examining how cellular preferred directions (as determined by the center-out task) change with posture. Several key experimental findings have resulted that constrain hypotheses about how motor cortical cells encode movement information. But while the significance of shifts in preferred direction is well known and widely accepted, posture-dependent changes in the depth of modulation of a cell's tuning curve--that is, gain changes--have not been similarly identified as a means of coordinate inference. This article develops a vector field framework in which the preferred direction and the gain of a cell's tuning curve are viewed as dual components of a unitary response vector. The formalism can be used to compute how each aspect of cell response covaries with posture as a function of the coordinate system in which a given cell is hypothesized to encode its movement information. Such an integrated approach leads to a model of motor cortical cell activity that codifies the following four observations: (i) cell activity correlates with hand movement direction; (ii) cell activity correlates with hand movement speed; (iii) preferred directions vary with posture; and (iv) the modulation depth of tuning curves varies with posture. Finally, the model suggests general methods for testing coordinate hypotheses at the single-cell level and simulates an example protocol for three possible coordinate systems: Cartesian spatial, shoulder-centered, and joint angle.

Animals↗
PubMed1995

Postural hypotension in diabetic autonomic neuropathy: a review.

Postural hypotension is uncommon in diabetes but can occur secondary to autonomic neuropathy. Symptoms are rare and include dizziness, weakness, blurred vision, tiredness, and loss of consciousness. The pathophysiology of postural hypotension is not clear, but changes in intravascular volume, heart rate, cardiac output, and splanchnic vascular resistance are similar in patients and controls. The main factors producing hypotension are a blunted catecholamine response to standing, and failure of lower limb vascular resistance to increase adequately. Treatment for symptomatic postural hypotension includes avoidance of dehydration, adequate salt intake, and fludrocortisone. Other treatments are reviewed but are less helpful. Patients with postural hypotension have intermittent symptoms over the years but rarely become severely disabled. They have a poorer prognosis than patients with symptomatic autonomic neuropathy without postural hypotension.

Autonomic Nervous System↗
PubMed1989

Posture and nocturnal asthma.

To investigate whether the supine posture caused sustained bronchoconstriction and could thus contribute to the development of nocturnal asthma, nine patients with nocturnal asthma were studied on two consecutive days, lying supine for four hours on one day and sitting upright for four hours on the other, the order of the two postures being randomised. Peak expiratory flow (PEF), forced expiratory volume in one second (FEV1), and forced vital capacity (FVC) were measured immediately before and after the four hours and over the subsequent hour. There was no significant difference between the erect and supine posture for PEF (248 v 248 l/min), FEV1 (1.31 v 1.22 l), or FVC (2.34 v 2.28 l) at the end of the four hours, nor did any significant change develop subsequently. Thus the supine posture is not associated with prolonged bronchoconstriction. As each patient had previously shown an average overnight fall in PEF of more than 20%, this study strongly suggests that the supine posture is not an important cause of overnight bronchoconstriction.

Adult↗