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PubMed1984

Effect of posture on inter-regional distribution of pulmonary ventilation in man.

Regional ventilation per unit alveolar volume (V/VA) and regional lung expansion (FRCR/TLCR) were measured in twelve normal male human subjects in seated, supine, lateral decubitus and prone postures using a gamma camera and inhalation of the radioactive gases 81Krm (half-life 13 sec) and 85Krm (half-life 4.4 h). FRCR/TLCR decreased from superior to inferior in all postures except prone where it was uniform; V/VA increased from superior to inferior except in the prone position where it was uniform. In the horizontal axis FRCR/TLCR and V/VA were uniformly distributed except for cranial to caudal gradients (with lower values caudally) in supine and lateral decubitus postures. In the prone posture V/VA tended to be higher in caudal lung zones.

Adult↗
PubMed1983

Posture-independent sensorimotor analysis of inter-hemispheric receptor asymmetries in neostriatum.

Nigrostriatal dopaminergic neurons are thought to be critically important for somato-sensorimotor behavior. Following unilateral irreversible elimination of these neurons, an animal shows an ipsiversive postural bias and permanently fails to orient its head toward tactile stimuli placed on the contralateral side of the body. In response to apomorphine, a dopamine agonist, these rats display contraversive circling. This effect is thought to reflect denervation-induced proliferation of dopamine receptors in the ipsilateral striatum. We have developed a sensitive procedure that measures sensorimotor function independent of postural and circling biases. We record the latencies to remove small pieces of adhesive stimuli placed onto the snout or radial surface of the forelimbs. The stimuli are placed symmetrically and simultaneously, which is analogous to tactile-extinction procedures used clinically. In the first study we found that rats with unilateral 6-hydroxydopamine (6-OHDA)-induced lesions of the nigrostriatal pathway showed a contralateral sensorimotor bias in response to doses of apomorphine below those necessary to produce contraversive circling. In a second study, unilateral striatal microinjections of kainic acid (KA) were used to destroy the neurons on which the postsynaptic dopaminergic receptors of the nigrostriatal system are contained. Compared to 6-OHDA, KA produced unexpected results in standard orientation tests. None of the KA-treated rats showed contralateral neglect, and some even showed ipsilateral deficits. However, the standard orientation tests are confounded by postural asymmetries, which were irregular in the KA-treated group. Using again the posture-independent sensorimotor procedure, we found that all KA-treated rats, like the 6-OHDA-treated rats, uniformly displayed ipsilateral sensorimotor biases. Sensorimotor function relating to inter-striatal asymmetries may be more specifically assessed with the bilateral-adhesive tests.

Animals↗
PubMed1983

Restraint alters the thermic response to morphine by postural interference.

The effects of morphine on body temperature have been shown to be altered by restraint. The purpose of this study was to determine how the type of restraint alters body temperature measurements and whether restraint alters the effects of morphine on body temperature by interfering with the ability of the rats to adjust their posture. The thermic effects of 5 doses of morphine (3.8 to 45 mg/kg) were compared in two types of restraint and confinement to a 13 X 20 X 20 cm pan without restraint. In unrestrained rats, morphine caused predominantly hyperthermia, but with restraint morphine caused hyperthermia at low doses and hypothermia at higher doses. Morphine hypothermia was greater in rats restrained in a wire-mesh restrainer which prevented heat and humidity build-up than in the commonly used plastic restrainer. In the unrestrained rats, morphine treatment was associated with a posture characterized by exophthalmos, immobility, a hunched position and increased muscle tone. Restrained rats could not assume a compact posture. These results suggest that restraint alters the thermic effect of morphine mainly by interfering with postural mechanisms which reduce heat loss.

Animals↗
PubMed1986

Postural asymmetry and lateralized rotation in normal rats administered apomorphine.

The study examines the hypothesis that the direction of circling exhibited by normal rats administered apomorphine reflects a drug-induced bias to use one specific hindleg for stepping and the other one for postural support. Results indicate that a majority of rats injected with this dopamine receptor agonist do show an asymmetry in the usage of the hindlegs (postural bias). However, the side of more frequent steppings does not predict the direction of circling. Moreover, postural bias may exist without lateralized circling. It is suggested that lateralized circling and postural asymmetry are two of several biases induced by apomorphine that may coexist in individual rats.

Animals↗
PubMedDate not supplied

The control of posture and movements during REM sleep: neurophysiological and neurochemical mechanisms.

Mammalian sleep is characterized by synchronized sleep, in which high-amplitude, low-frequency waves appear in the electroencephalogram, and desynchronized sleep, characterized by small-amplitude, high-frequency waves, absence of tonic muscle activity, and rapid eye movements (REM), which are associated in humans with dreams. The postural atonia typical of desynchronized sleep is due to postsynaptic inhibition of spinal motoneurons resulting from tonic activation of a bulbospinal inhibitory system. Superimposed on this background of postural atonia, a motor pattern appears, characterized by rapid contractions of the limb musculature synchronous with the REM bursts. Simultaneously one observes phasic inhibition of transmission of somatic afferent volleys to motoneurons and ascending spinal pathways. The bursts of REM depend upon rhythmic discharges of vestibulo-oculomotor neurons, due to extralabyrinthine volleys originating from the brainstem. Ascending and descending vestibular volleys are also able to excite corticospinal and other supraspinal descending neurons responsible for the motor events synchronous with the bursts of REM. Activation of cholinergic neurons located in the brainstem reticular formation reproduces the postural atonia typical of desynchronized sleep, as well as the phasic events characterized by the REM bursts and the related changes in spinal cord activities. Even in this instance the bursts of REM and the related spinal effects depend upon rhythmic changes in the discharge of vestibular nuclear neurons. Experimental evidence indicates that the cholinergic reticular neurons fire asynchronously, thus being able to trigger the bulbospinal inhibitory system responsible for postural atonia. Even the vestibulo-oculomotor neurons are activated by these cholinergic reticular neurons; however, the continuous stream of these extralabyrinthine impulses is transformed into rhythmic changes of discharge of the vestibular nuclear neurons due to the presence of inhibitory neurons interposed with the vestibulo-oculomotor system. Waxing and waning in the activity of these cholinergic reticular neurons accounts for the regular occurrence of the cholinergically induced bursts of REM.

Adrenergic Uptake Inhibitors↗
PubMed1981

Does postural asymmetry indicate directionally of rotation in rats: role of sex and handling.

Postural asymmetry of male and female Wistar rats was assessed during 4 tests: (a) tail suspension, (b) tail holding, (c) tail pinch and (d) walking on a narrow path. The tests were conducted prior to and after (+)-amphetamine (1 mg/kg, i.p.) administration. Rotational directionality was assessed in a rotometer. Only in female rats did postural adjustment during the tail-pinch predict with borderline significance the direction of circling prior to and after amphetamine. In both surgically castrated and conjugated estrogen-treated male rats, in sham-castrated and handled males, the tail-pinch test caused the same dominant directionality as rotation under amphetamine. The duplicity of postural tests suggests that there is a multitude of systems controlling and modulating postural response.

Animals↗
PubMed1985

Lateralizing effects of apomorphine on taxis, postural support and rotation in rats.

Subcutaneous injections of apomorphine, a dopamine receptor agonist, induced a lateralization of taxis for edges in 16% of rats and a reliable lateralization of postural support in 82% of rats. The relation among these effects and the lateralizing effects of apomorphine on rotational behavior were examined. Lateralized rotation did not reliably correlate with lateralized taxis. However, it correlated with a relatively large asymmetry of postural support. The lateralizing effects of apomorphine on taxis and rotation may reflect attentional and directional asymmetries, respectively. It is proposed that apomorphine can induce different types of lateralizations, including attentional, postural and directional, and that the lateralizing effects of apomorphine on posture and locomotor direction are interrelated. Regional brain interhemispheric asymmetries in the responsiviness of dopamine receptors may underlie different types of apomorphine-induced lateralizations.

Animals↗
PubMed1982

Abnormalities in postural reflexes and voluntarily induced automatic movements in Parkinson patients.

Postural abnormalities were systematically studied in 41 Parkinson patients in relation with the other Parkinson symptomatology. Evidence was collected that kinetic postural mechanisms, including turning in recumbant position, rising from the floor and walking, to be considered as volitional automatic movements, reacted differently on Levodopa therapy compared with static postural reflexes and the classical Parkinson symptoms. This suggests that the neuro-biochemical substrate of these postural movements may involve other than dopaminergic pathways as well.

Basal Ganglia↗
PubMed1987

Motor activity and visually induced postural reactions during two-g and zero-g phases of parabolic flight.

Maintenance of an upright posture was measured in human subjects during increased and decreased gravitoinertial force phases of parabolic flight. Upright posture was maintained by tonic activity of the ankle joint extensor muscle (soleus) during the one-g or two-g phases. During the zero-g phase the same posture was maintained primarily by activity of the flexor muscle (tibialis). Downward and upward optokinetic stimulation induced strong postural reactions directed forwards and backwards, respectively. These reactions were accompanied by changes of motor activity of the flexor muscle. This suggests a rapid redistribution of motor programs between extensor and flexor muscles with an increase in visual input influence, and confirms results obtained during space flight.

Gravitation↗
PubMed1984

The postures exhibited by 3-day-old full term neonates.

A carefully selected sample of 18 3-day-old full term neonates was videotaped in 3 different positions. The time of taping was controlled for feed interval. These tapes were then analysed for state and posture using a frame by frame facility. Seventy one separate postures were documented and the existence of a 'neutral posture' was noted. These postures will provide a baseline for further work in adult-infant interaction.

Eating↗
PubMed1991

Posture and the circulation: the age effect.

The primary instigator of circulatory response to the upright posture is the rapid displacement of about 10% of blood volume from the thorax to the lower body. The resultant hemodynamic deficit induces postural intolerance, especially orthostatic hypotension, in elderly over 70 years of age and in some young subjects after exposure to weightlessness. In this review, our objectives have been: 1) to describe in the normal subject the hemodynamic consequences of the headup posture, as well as lower body negative pressure, the compensatory responses intended to cope with these stresses, and their mechanisms; 2) to outline the effect of age on the circulatory responses to these stresses; and (3) to analyze and compare the tests currently used to assess circulatory tolerance. Our ability to design effective countermeasures to orthostatic circulatory intolerance is severely handicapped by our inadequate knowledge of the basic hemodynamic events incident to normal and abnormal orthostatic tolerance. We believe that better understanding and standardization of the postural tests, better experimental design to include greater emphasis on inter and intra-individual variability, and wider application of currently available noninvasive circulatory techniques would greatly improve the prospects for success in this research area.

Adaptation, Physiological↗
PubMed1987

Automated contingent reinforcement of correct posture.

This study evaluated the effectiveness of a mercury switch as a self-monitoring device to improve the sitting posture of an adult male. The participant in this study was a 31 year old man who was blind, nonambulatory, and who had been classified in the moderate range of intellectual functioning and in the severe range of adaptive functioning due to physical impairments. After determining that music practice and listening to a game show on the television channel of a radio were powerful reinforcers, a multiple baseline across the two reinforcing activities was implemented. The participant wore a mercury switch inside of a baseball cap which activated a Casio keyboard during music practice and a radio during the independent leisure activity of listening to a game show. During the treatment condition, the keyboard and radio were activated automatically by upright sitting posture. Results indicated that the participant's sitting posture increased from an average of almost 0% correct upright posture during baseline to an average of 52% during treatment.

Adult↗
PubMed1995

Postural modulation of the soleus H reflex in young and old subjects.

The influence of different static postures on the soleus H reflex was assessed in 15 old (mean age = 76.3 years) and 10 young (mean age = 24.2 years) subjects. H reflex and M wave recruitment curves were obtained under 2 randomly administered conditions: (1) standing; and (2) prone. Once in place, the recording and stimulating electrodes were not removed until the completion of testing, to ensure that exact placement was maintained. A 1 msec current pulse was given transcutaneously to elicit the H reflex and M response. Static postural sway area (cm2) was assessed on a Kistler force platform using custom software (sample rate = 50 Hz/15 sec trials). Results demonstrated that the young subjects reduced the amplitude of the H reflex from the prone (Hmax/Mmax = 73.6%) to the standing (Hmax/Mmax = 59.9%) condition, whereas the old subjects did not (prone = 32.4%, standing = 38.2%). However, within the old group, 2 subgroups emerged--those who depressed the reflex similar to the young subjects (O-D, n = 6) and those who did not depress the reflex (O-ND, n = 9). Furthermore, there were significant differences in postural sway scores between the young and old, between the O-D and O-ND, but not between the O-D and young groups. These results suggest differences in the manner in which young and old subjects modulate the soleus H reflex when standing, and support the view that modulation of the stretch reflex may be important in the control of static posture.

Adult↗
PubMed2005

A multi-disciplinary study of the ocular, orthopedic, and neurologic causes of abnormal head postures in children.

PURPOSE: To determine the relative frequency that abnormal head postures in children are caused by orthopedic, ophthalmologic, or neurologic disorders, respectively. DESIGN: A prospective, consecutive case series. METHODS: Children found to have an abnormal head posture on routine pediatric examination underwent an evaluation by a pediatric ophthalmologist, pediatric orthopedist, and pediatric neurologist. The study was conducted in northwestern Italy. RESULTS: In the 63 children evaluated, the cause of the abnormal head posture was orthopedic in 35, ocular in 25, and neurologic in 5. In 8 patients, no specific cause could be found. The most common orthopedic cause was congenital muscular torticollis, which accounted for 31 patients. The most common ocular cause was superior oblique muscle palsy, which accounted for 12 patients. In 2 patients neck muscle contracture suggested an orthopedic cause, however, the tight neck muscles were secondary to a head tilt caused by superior oblique muscle palsy. CONCLUSIONS: When the cause of an abnormal head posture is not obvious, a multi-disciplinary approach including ophthalmologic, neurologic, and orthopedic specialists may be helpful.

Child, Preschool↗
PubMed2006

[Maternal postures and epidural analgesia during labour].

The evolution of birth is of interest for obstetricians and midwives. Postures with asymmetric stretching and balance, kneeling, or sitting have been claimed to be able to help foetal head rotation. Although walking during labour have no influence on the outcome of labour, hip-flexed postures enlarging the pelvic diameter are yet evaluated to improve the obstetric course of labour. In a prospective randomised study including 93 parturients, we compared the supine 30 degrees lateral tilt (control group) to three hip-flexed postures: sitting (S), right hip-flexed left lateral position (L) and left hip-flexed right lateral position (R). Epidural analgesia with 12 ml ropivacaine 0.1% and sufentanil 0.5 microg/ml was administered over a period of six minutes. The total epidural spread was 15+/-0.3 dermatomes and the upper level of thermo-analgesic blockade reached T7-T8 (T5 to T10) in each group. There were no differences between groups for the left and right total spread and upper level of epidural blockade, for the time to maximal block and pain relief. There was no motor block and no maternal or foetal side effects. We conclude that, for the three hip-flexed postures tested, position does not influence local anesthetic spread or symmetry of analgesia after induction of obstetric epidural anaesthesia.

Amides↗
PubMed2004

The effect of upper extremity support on upper extremity posture and muscle activity during keyboard use.

Forearm support during keyboard use has been reported to reduce neck and shoulder muscle activity and discomfort. However, the effect of forearm support on wrist posture has not been examined. The aim of this study was to examine the effect of 3 different postures during keyboard use: forearm support, wrist support and "floating". The floating posture (no support) was used as the reference condition. A wrist rest was present in all test conditions. Thirteen participants completed 20 min wordprocessing tasks in each of the test conditions. Electromyography was used to monitor neck, shoulder and forearm muscle activity. Bilateral and overhead video cameras recorded left and right wrist extension, shoulder and elbow flexion and radial and ulnar deviation. The forearm support condition resulted in significantly less ulnar deviation (p < or = 0.007), less time spent in extreme ulnar deviation (p = 0.002) and less reports of discomfort than the "floating" condition (p = 0.002). The wrist support but not the forearm support condition resulted in less trapezius and anterior deltoid muscular activity (p < 0.007). These findings indicate that typing with upper extremity support in conjunction with a wrist rest may be preferable to the "floating" posture implicit in current guidelines.

Adolescent↗
PubMed2005

Concordance between VDU-users' ratings of comfort and perceived exertion with experts' observations of workplace layout and working postures.

The aim of the present study was to evaluate the concordance (agreement) between VDU-users' ratings of comfort and ergonomists' observations of workplace layout, and the concordance between VDU-users' ratings of perceived exertion and ergonomists' observations of working postures during VDU-work. The study population consisted of 853 symptom free subjects. Data on perceived comfort in different dimensions and data regarding perceived exertion in different body locations were collected by means of a questionnaire. Data concerning workplace layout and working postures were collected with an observation protocol, by an ergonomist. Concordance between ratings of comfort and observations of workplace layout was reasonably good for the chair and the keyboard (0.60, 0.58) and good regarding the screen and the input device (0.72, 0.61). Concordance between ratings of perceived exertion and observations of working postures indicated good agreement (0.63-0.77) for all measured body locations (neck, shoulder, wrist and trunk). In conclusion ratings of comfort and perceived exertion could be used as cost-efficient and user-friendly methods for practitioners to identify high exposure to poor workplace layout and poor working postures.

Adult↗
PubMed2004

Evaluation of postural stability in the elderly with stroke.

OBJECTIVE: To compare clinical and biomechanical measures of balance in elderly stroke patients with those of healthy elderly people. DESIGN: Two-group comparison design. SETTING: Laboratory environment. PARTICIPANTS: Fifteen poststroke patients and 15 healthy age-matched older adults (N=30). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The biomechanical variable COP-COM, which represents the distance between the center of pressure (COP) and the center of mass (COM) in terms of root mean square. The mean of 4 trials of the COP-COM variable for each test condition was used for statistical analysis. Furthermore, the different systems (sensory, motor, central processor) related to postural stability were evaluated. RESULTS: Statistical significance of the COP-COM variable was larger in the stroke group than in healthy subjects, in both the anteroposterior (AP) and mediolateral (ML) directions. Furthermore, statistically, stroke subjects showed amplitudes of the COP-COM variable that were significantly larger in the eyes-closed condition. The significant negative correlation demonstrated between COP-COM amplitude and the balance scales (Berg, Tinetti) indicated that the patients with larger COP-COM amplitudes had lower clinical balance score. Furthermore, correlation coefficient scores between COP-COM variables in both AP and ML directions and motor performance using Fugl-Meyer Assessment (rho=-.53, rho=-.51, respectively) and reaction time (rho=-.53, rho=-.44, respectively) were significant. Vibration (rho=.41) and touch-pressure (rho=.42) perception thresholds correlated significantly only in the AP direction. CONCLUSIONS: Evaluating postural stability with COP-COM variable provided an accurate measure of postural stability in poststroke elderly people. Furthermore, postural stability in quiet stance, as measured by COP-COM amplitude, was related to functional measures of balance as well as physiologic factors relating to balance, such as visual conditions, lower-extremity peripheral sensibility, motor recovery, and simple reaction time.

Aged↗