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PubMed1996

Taping of the ankle--the effect on postural sway during perturbation, before and after a training session.

The application of adhesive tape to the ankle prevents sprains and is therefore frequently used by athletes with functional instability of that joint. The purpose of the study was to investigate the effect of taping on postural sway during a sudden perturbation in subjects with unilateral functional instability of the ankle joint. Nine Swedish male elite soccer players with unilateral functional instability of the ankle joint after a sprain participated in the study. Their mean age was 25 years. All but one had sustained an ankle sprain during the last 1-12 months, and they applied adhesive tape on one ankle at every practice session and game. Eight moderately active male subjects served as controls (mean age 32 years). Recording and analysis of postural sway was performed by the use of stabilometry. We used a device previously tested for reliability and added a perturbation device. The perturbation device was an ankle disc standing on four bars on top of the force plate. At the start of each recording, the ankle disc was stable. The bars could be removed simultaneously by the test leader. The following parameters were analysed: (1) max sway, the maximal sway amplitude upon perturbation in mediolateral and anteroposterior directions; (2) mean sway, the mean sway during the recording in mediolateral and anteroposterior directions. There was no difference between the right and left ankles before the practice session. The postural sway during perturbation (max sway) decreased when the ankle was taped before the exercise. After the exercise there was no difference between the taped and untaped ankles. The maximum and mean amplitude of sway without tape were smaller after exercise than before exercise. The results in the present study indicate a positive effect of tape on postural sway during perturbation before a practice session. The decreased sway with an untaped ankle after the practice session could mean that the prophylactic effect of taping is most important during the first part of a practice session or a game. Warmer muscle units mean less uncontrolled muscle activity which could result in more effective stabilisation of the ankle joint.

Adult↗

PubMed1996

Effects of extreme lateral posture on hemodynamics and plasma atrial natriuretic peptide levels in critically ill patients.

OBJECTIVE: To quantify the hemodynamic effects of turning critically ill, mechanically ventilated patients to the extreme left and right lateral postures. DESIGN: Prospective investigation. SETTING: Eight-bed intensive care unit in a university hospital. PATIENTS: Twelve consecutive patients presenting with severe respiratory failure and requiring continuous positive inotropic support. INTERVENTIONS: All patients were mechanically ventilated and placed in a kinetic treatment system. They were positioned in the supine, left dependent, and right dependent postures, resting for 15 min in each position. MEASUREMENTS AND RESULTS: Hemodynamic measurements, assessments of right ventricular function, and determinations of intrathoracic blood volume were performed in three different positions. Concentrations of atrial natriuretic peptide in plasma were quantified. In three patients, the findings were controlled by transesophageal echocardiography. Cardiac index [median (range) 5.5 (3.2-8.1) vs 4.3 (3.2-7.5) l/min per m2, p < 0.01], intrathoracic blood volume [1125 (820-1394) vs 1037 (821-1267) ml/m2, p < 0.01], and right ventricular end-diastolic volume [130 (83-159) vs 114 (79-155) ml/m2, p < 0.05] increased significantly in the left dependent position compared to supine. Mean arterial pressure did not change. Atrial natriuretic peptide levels rose from 140 to 203 pg/ml. In the right dependent position, we found a marked decrease in the mean arterial pressure [85 mmHg (supine) to 72 mmHg (right dependent), p < 0.01]. Cardiac index and intrathoracic blood volume were unchanged, but right ventricular end-diastolic volume decreased from 114 to 102 ml/m2 (p < 0.05). Additionally, atrial natriuretic peptide levels decreased significantly (median delta value: 37 pg/ml). In echocardiographic controls we found an increase in right ventricular end-diastolic diameters in the left dependent position and shortened diameters in the right dependent position. CONCLUSIONS: Extreme lateral posture affects the cardiovascular system in critically ill, mechanically ventilated patients: in the left dependent position a "hyperdynamic state" is reinforced, while the right decubitus position impairs right ventricular preload and predisposes to hypotension. Echocardiography and changes in plasma atrial natriuretic peptide values indicate that these findings are due to altered distensibility of the right ventricle caused by regional intrathoracic gravitational changes. We conclude that the duration and the angle of lateral posture should be restricted in hemodynamically unstable patients.

Acute Disease↗

PubMed1995

Comparison of autonomic function using Valsalva ratio and 30:15 postural ratio prior to and after haemodialysis treatment.

In published studies of chronic haemodialysis patients, the frequency of autonomic dysfunction varies widely. One reason for the variation may be the time of testing with respect to time of dialysis. The current study tests the hypothesis that autonomic function--as measured by heart rate responses to the Valsalva manoeuvre (Valsalva ratio) and 30:15 electrocardiogram (ECG) R-R interval to upright posture (postural ratio)--is different when patients are above 'dry weight' (predialysis) than when they are at or below dry weight (postdialysis). The study also reviews available literature to analyze other factors that may affect the results of autonomic testing in this population. A total of 25 chronic haemodialysis patients underwent standard Valsalva and 30:15 R-R interval postural autonomic testing prior to and after haemodialysis. In addition, pre- and postdialysis orthostatic responses were measured and compared with a control population. The 30:15 ratio increased after dialysis (p = 0.001). The Valsalva ratio did not change with dialysis. Out of 25 subjects, seven had an abnormal 30:15 ratio prior to dialysis decreasing to two out of 25 patients postdialysis (p < 0.03). Orthostatic responses predialysis did not differ from those in the control group. Review of the literature shows great variability in definition of normal Valsalva and postural (30:15 R-R interval) ratios. Diabetic patients in the current and prior studies were more likely to have abnormal responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

[The pulse-respiratory quotient of persons with stable and instable postural circulation while standing (author's transl)].

The pulse-respiratory quotient of patients with postural circulatory instability is the same in a prone position as that of patients with stable postural circulation, however, it is higher in an upright postiion. This is not only caused by the higher pulse frequency of postural circulatory instable patients while standing, but also by the lower respiratory rate. The difference of the pulse-respiratory quotient between standing and lying indicates with more accuracy the diagnosis of postural circulatory instability. The severity of the symptoms is related not only to the pulse and respiratory rate, but also to the pulse-respiratory quotient. Tachycardiac patients with a high pulse-respiratory quotient show clinically symptoms more severe than tachycardiac patients with lower pulse-respiratory quotients. Due to the results shown here, the terms of rhythmical concordance and discordance are proposed.

Adolescent↗

PubMed1996

Origin of atypical reflux symptoms. A case study showing the importance of reflux composition and posture.

In summary we evaluated a 39-year-old man two years after partial esophagectomy and gastroesophageal anastomosis. He had developed recurrent Barrett's esophagus and atypical reflux symptoms. We found free reflux and no antireflux barrier at the hiatus or the esophagogastric anastomosis. Three different reflux techniques performed simultaneously demonstrated that the composition of refluxant varied with posture, explaining the atypical nature of the symptoms. In the left recumbent posture, the refluxate was comprised of acidified liquid and gaseous gastric contents with the patient complaining of heartburn and chest pain. In the right recumbent posture the refluxate was composed of only nonacidic gas, and the patient complained of chest pain without heartburn. We propose that multiple reflux tests performed simultaneously in the setting where a patient experiences his atypical symptoms may help clarify their origin. Furthermore, this case illustrates how posture may dramatically influence refluxant composition.

Adenocarcinoma↗

PubMed2001

Postural tachycardia syndrome in syringomyelia: response to fludrocortisone and beta-blockers.

Orthostatic intolerance is occasionally reported by patients with syringomyelia and is usually attributed to vestibular symptoms or neurogenic orthostatic hypotension. Postural tachycardia syndrome has not been previously described in syringomyelia. A patient with long-standing syringomyelia and a Chiari type I anomaly developed disabling "panic-like" attacks associated to orthostatic intolerance five years after posterior fossa decompression and shunting of the syrinx. A head-up tilt test showed an early phase of postural orthostatic tachycardia followed by progressive arterial hypotension and bradycardia as seen in neurally mediated syncope. A magnetic resonance imaging scan showed a collapsed syrinx from the 3rd cervical to the 12th thoracic vertebra without syringobulbia. Fludrocortisone and beta-blockers led to resolution of symptoms. Partial sympathetic denervation of the legs in syringomyelia might explain the occasional occurrence of postural tachycardia syndrome. Postural tachycardia syndrome may be included as a possible cause of orthostatic symptoms in syringomyelia patients.

Adrenergic beta-Antagonists↗

PubMed2005

Human standing posture control system depending on adopted strategies.

Control of the standing posture of humans involves at least two distinct modes of operation to restore the body balance in the sagittal plane: the ankle strategy and the hip strategy. The objective of the study was to estimate the contribution of vestibular, visual and somatosensory feedbacks to these distinct strategies. The body dynamics was described as the motion of two linked rigid segments that represented the legs and the rest of the body. The posture controller received the inclination angles of the two body segments as inputs and regulated the moments around the ankle and hip joints. The controller had four feedback paths that were characterised by transfer functions connecting the two inputs and the two outputs. To evoke the distinct strategies, the floor conditions were varied by narrowing the support surface under the feet. A continuous pseudo-random external disturbing force was applied to the waist and the thigh independently. The inclination angles of the body segments and the ground reaction force were measured, and the transfer functions of the controller were estimated with the maximum-likelihood system identification procedure. Six healthy male adult subjects participated in the experiment. When the hip strategy became evident under the narrow support surface conditions, the transfer function relating the leg inclination angle and the ankle joint moment decreased its DC gain (16%), whereas the other three transfer functions increased the gains (20-140%) (ANOVA, p < 0.05). Based on a criterion for simplicity in the modification of the posture controller, these changes suggest a new hypothesis that, when posture control becomes difficult, the central nervous system selectively activates the somatosensory feedback paths from the hip joint angle to the moments around the ankle and hip joints.

Adult↗

PubMed1989

Effects of vibration on arm and shoulder muscles in three body postures.

The electromyographic responses of arm and shoulder muscles to vibrations were studied in three postures similar to the postures of drilling in a ceiling, drilling in a wall and drilling in a floor. This experiment was performed within the defined parameters of: vibrational frequency at 30 Hz, acceleration level 40 m.s-2 (rms), pushing force expressed as percentage maximal voluntary contraction, and gripping force which was set at 100 N. The exposure time for each test was 5 min. The general findings from these three body postures show that all the examined muscles were affected by exposure to vibration. The EMG index increased as follows: trapezius muscle 39% (p less than 0.05), lower-arm flexor muscles 23% (p less than 0.05), infraspinatus muscle 14% (p less than 0.05), lower-arm extensor muscles 14% (p less than 0.1) and biceps muscle 6% (p less than 0.1). The muscle most affected by vibration was found to be the trapezius muscle. It should be taken into consideration that vibration can be a contributing factor in neck/shoulder disorders among power handtool operators. The general conclusion from this study is that changes in working posture give different transmissions of vibration in the upper extremities. It seems as if the prime movers and muscles with an increased muscle length or increased degree of contraction are most affected by vibration.

Adult↗

PubMed1996

Possible relationship between chronic fatigue and postural tachycardia syndromes.

Postural tachycardia syndrome refers to the development of symptoms such as light-headedness, visual blurring, palpitations and weakness on assuming an upright posture; these symptoms are relieved by resuming a supine posture. This syndrome is occasionally associated with idiopathic hypovolemia, impaired vasomotor tone, deconditioning and autonomic neuropathy, but has not been reported in association with chronic fatigue syndrome (CFS). We describe five patients who satisfied the CFS criteria of the Centres for Disease Control and Prevention. Upright tilt-table testing induced significant hypotension and increased heart rate in all five patients, consistent with clinical and autonomic manifestation of postural tachycardia syndrome.

Adult↗

PubMed2000

Compensatory head posture changes in patients with obstructive sleep apnea.

The upper airway narrowing and changes in head posture and their relationship with apnea severity in patients with obstructive sleep apnea (OSA) were investigated. In 86 male OSA patients and 37 healthy men, one-night polysomnographic examination was performed and a lateral cephalogram by digital image processing system was taken in each subject. Fifteen variables concerning the upper airway dimensions, area and head postures were measured by using a computer software (NIH Image). The results showed that upper airway dimensions in the OSA group at all levels were significantly smaller than those in the control group and the results hold true when the age and body mass index were well controlled in these two groups. Significant forward inclination of the cervical column was found in the patients with an apnea index (AI) greater than 35 episodes/h. And changes in the head posture variables in the whole study group were significantly correlated with AI and airway dimensions at various levels. It was suggested that there exist significant and extensive upper airway narrowing in OSA patients even in upright position and awake state; And as the apnea severity progresses, patients may assume certain compensatory head postures in an attempt to maintain an adequate airway patency.

Adaptation, Physiological↗

PubMed1997

Load assessment of the static posture and weight holding in terms of pulmonary ventilation and heart rate.

The aim of this study was to explore appropriate index for load evaluation by analyzing the changes of pulmonary ventilation (VE) and heart rate (HR) in 35 student volunteers under the condition of static posture and weight holding. Each subject was asked to perform 7 kinds of static postures and 2 kinds of weight holdings. The HR was continuously measured by a remote detecting device. VE was recorded by a ventimeter for an average of 5 min. The results showed that HR was positively correlated to VE under static activities (r = 0.89), which suggested that VE as well as HR could to some degrees reflect the static load. It was better to use VE to indicate the load of weight holdings than to use HR, which, on the other hand, was more sensible in reflection of the posture load. It is better to use relative value of both of VE and HR to reflect the static load. In addition, arm-overheaded posture increase HR more significantly than any other activities.

Adult↗

PubMed1997

Anticipatory postural adjustments in stance and grip.

The reactive forces and torques associated with moving a hand-held object between two points are potentially destabilising, both for the object's position in the hand and for body posture. Previous work has demonstrated that there are increases in grip force ahead of arm motion that contribute to object stability in the hand. Other studies have shown that early postural adjustments in the legs and trunk minimise the potential perturbing effects on body posture of rapid voluntary arm movement. This paper documents the concurrent evolution of grip force and postural adjustments in anticipation of dynamic and static loads. Subjects held a manipulandum in precision grasp between thumb and index finger and pulled or pushed either a dynamic or a fixed load horizontally towards or away from the body (the grasp axis was orthogonal to the line of the load force). A force plate measured ground reaction torques, and force transducers in the manipulandum measured the load (tangential) and grip (normal) forces acting on the thumb and finger. In all conditions, increases in grip force and ground reaction torque preceded any detectable rise in load force. Rates of change of grip force and ground reaction torque were correlated, even after partialling out a common dependence on load force rate. Moreover, grip force and ground reaction torque rates at the onset of load force were correlated. These results imply the operation of motor planning processes that include anticipation of the dynamic consequences of voluntary action.

Adult↗

PubMed2003

[Secondary cranial extension after spinal anesthesia with isobaric 0.5% bupivacaine following postural change].

Inadvertent cranial extension of sympathetic and sensory block following posture change during spinal anaesthesia has been reported for isobaric as well as for hyperbaric local anaesthetics. We present the case of a patient who underwent surgical repair of a refracture of the tibia under spinal anaesthesia with 17.5 mg of isobaric 0.5% bupivacaine. The maximum level of sensory block (MLSB) reached T8 after 15 min. Following posture change into a 15 degrees anti-Trendelenburg position 35 min after lumbar puncture, the MLSB increased cranially for 10 segments and reached the C6 level after 10 min of anti-Trendelenburg position. The patient suffered from severe bradycardia and arterial hypotension which were treated with 6% hydroxyethyl starch, atropine and Akrinor. In addition, the patient developed respiratory insufficiency and was therefore intubated and the lungs were mechanically ventilated. The operation was performed uneventfully with the patient under general anaesthesia. At the end of surgery the trachea was extubated, and the patient was awake with stable hemodynamics, sufficient spontaneous ventilation and free of pain. MLSB reached the second lumbar dermatome. This case shows that after assumed fixation of the local anaesthetic an inadvertent extension of the MLSB following posture change is possible. Close surveillance is recommended for patients with central neuraxial blocks until the block is in complete remission. The mechanisms for inadvertent high extension of the MLSB following posture change are discussed.

Anesthesia, General↗

PubMed2002

The effect of perturbation acceleration and advance warning on the neck postural responses of seated subjects.

The muscle and kinematic responses of subjects exposed to postural perturbations have been shown to vary with platform acceleration when this acceleration was covaried with platform velocity or displacement. The purpose of the current study was to isolate platform acceleration and examine its effect on the neck muscle response and head kinematics of seated subjects exposed to anterior perturbations. Thirty-six subjects (20 females, 16 males) underwent two blocks of 36 perturbations. Three different perturbations with peak accelerations of 7.7, 14.7, and 21.7 m/s(2) up to a common velocity of 0.5 m/s were used. In one block, subjects received an audible warning corresponding to the platform acceleration magnitude, and in the other block, no advance warning was given. Onset and amplitude of the sternocleidomastoid and cervical paraspinal muscle responses were measured using surface electromyography. Kinematic measures included linear and angular accelerations and displacements of the head. The results showed no differences in either the preperturbation posture or the muscle or kinematic responses between the warned and unwarned trials. Significant differences were observed in the onset and amplitude of the muscle and kinematic variables with perturbation acceleration, although these response differences were not linearly graded with perturbation acceleration. Gradation of muscle activation times has not been previously observed in postural perturbation studies, and their gradation with platform acceleration in the current study suggested that platform acceleration was a strong regulator of the reflex muscle response in postural perturbations.

Acceleration↗

PubMed2002

Central set influences on gait. Age-dependent effects of postural threat.

We tested the hypothesis that anxiety regarding the potential consequences of a possible fall would alter gait patterns differently between younger and older adults. Sixteen younger and fifteen older adults participated in this study. Participants walked at a self-determined velocity along a 7.2-m walkway under 4 different conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (0.60 m vs 0.15 m) and the height of the walking surface (floor vs elevated: 0 m vs 0.60 m). Results indicated that although both younger and older adults altered their gait patterns under conditions of increased postural threat, the movement adaptations observed among older adults were substantially different to those adopted by younger adults. These age-dependent differences were strongly evidenced in the joint kinematics and the variability of the gait pattern within each condition. Our findings also indicated that when postural threat increased, the level of muscle activation throughout the gait cycle was altered in the distal musculature (gastrocnemius m. and tibialis anterior m.) among older adults only. Based on the age-related differences observed, we believe that the gait pattern alterations observed among younger and older adults reflect central set modifications to postural control that are mediated by a heightened anxiety imposed by the constraints of the testing conditions. Based on the age-dependent differences in the observed gait pattern modifications, it appears that the effects of anxiety on the control of locomotion are more pervasive for older adults than for younger adults.

Accidental Falls↗

PubMed2002

Effects of different types of light touch on postural sway.

When a standing person applies a light finger touch to an external stable object, postural sway is reduced. We tested a hypothesis that two factors related to touch can induce this effect, the presence of a stable reference point and the modulation of contact forces leading to tissue deformation. Force platform signals were analyzed while subjects stood quietly with or without additional light touch to an external object (contact forces under 1 N). The point of touch on the body was manipulated. We also investigated the effects of active touch vs fixation of a finger at a point in external space. The results show that touch to the head or neck can be more effective in reducing body sway than a finger touch. A larger reduction in sway was observed when the finger was fixed in a clip (the net forces between the clip and the point of its fixation to the stand were under 1 N) as compared to a free light touch to a pad. The subjects showed a reduction in postural sway while holding a load suspended using a pulley system; in this situation, contact with the load via the pulley provided modulation of contact forces but not a fixed reference point. This finding emphasizes the importance of such factors as stability of the contact point and modulation of contact forces, as compared to active touch or to an implicit task of stabilizing the kinematic chain. The system of postural stabilization can reduce postural sway, making use of either of two sources of sensory information associated with touch, one related to providing a fixed reference point in space, and the other related to transient force changes at the point of contact related to the sway.

Acoustic Stimulation↗

PubMed2002

Vection increases the magnitude and accuracy of visually evoked postural responses.

Movement of large visual scenes induces an illusion of self-motion (vection) and postural responses. We investigated if the conscious perception of self-motion influences the magnitude and directional accuracy of visually evoked postural responses. Five normal subjects fixated the centre of a large disk rotating in the roll (coronal) plane. The disk was placed either in front of the subjects or obliquely 30 deg to their right or left; in these oblique positions disk fixation was achieved by horizontal ocular deviation alone (i.e. no neck deviation). Subjects indicated their subjective perceptual status, either vection or object motion, with a push button. The results confirmed that the direction of the visually evoked postural response was reoriented according to the different eye-disk positions. In addition, both the magnitude of the postural response and the accuracy of its alignment with the disk rotational plane were significantly increased during vection periods. The results show that conscious perception of self-motion enhances visuopostural performance. Since conscious perception is likely to arise at cortical levels, the findings indicate that the cortex is one of the sites where gaze direction interacts with retinal motion signals to provide a self-motion signal in body-centric co-ordinates. Such interaction provides a substrate for spatial representation during motion in the environment.

Adult↗

PubMed2003

Impaired postural compensation for respiration in people with recurrent low back pain.

This study evaluated the degree to which the disturbance to posture from respiration is compensated for in healthy normals and whether this is different in people with recurrent low back pain (LBP), and to compare the changes when respiratory demand is increased. Angular displacement of the lumbar spine and hips, and motion of the centre of pressure (COP), were recorded with high resolution and respiratory phase was recorded from ribcage motion. With subjects standing in a relaxed posture, recordings were made during quiet breathing, while breathing with increased dead-space to induce hypercapnoea, and while subjects voluntarily increased their respiration to match ribcage expansion that was induced in the hypercapnoea condition. The relationship between respiration and the movement parameters was measured from the coherence between breathing and COP and angular motion at the frequency of respiration, and from averages triggered from the respiratory data. Small angular changes in the lumbopelvic and hip angles were evident at the frequency of respiration in both groups. However, in quiet standing, the LBP subjects had a greater displacement of their COP that was associated with respiration than the control subjects. The LBP group had a trend for less hip motion. There were no changes in the movement parameters when respiratory demand increased involuntarily via hypercapnoea, but when respiration increased voluntarily, the amplitude of motion and the displacement of the COP increased in both groups. The present data suggest that the postural compensation to respiration counteracts at least part of the disturbance to posture caused by respiration and that this compensation may be less effective in people with LBP.

Adult↗