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PubMed1987

Postural suppression of plasma atrial natriuretic polypeptide concentrations in man.

The effects of sequential changes in posture, from recumbency, to sitting and then to the upright position, each for 60 min, respectively, on the levels of plasma immunoreactive atrial natriuretic polypeptide (ANP) in healthy human subjects were studied using a radioimmunoassay (RIA) method. At the end of each change in posture, plasma ANP levels were respectively 150 +/- 16.4 pg/ml (recumbent), 103 +/- 11.2 pg/ml (sitting), and 78.1 +/- 7.90 pg/ml (upright). In contrast, plasma renin concentration (PRC) and plasma aldosterone concentration (PAC) determined concomitantly with ANP showed a significant increase in response to the sitting and upright postures. Plasma ANP levels determined in normal subjects who remained in the recumbent posture for the same period did not show any significant change. This suggests that ANP is involved in the maintenance of haemodynamic homeostasis under physiological conditions and emphasizes that postural factors must be taken into account and controlled in order to evaluate plasma ANP levels properly, as well as those of PRC and PAC.

Adult↗
PubMed1985

An electromyographic study of the immediate effect of an occlusal splint on the postural activity of the anterior temporal and masseter muscles in different body positions with and without visual input.

With the mandible at rest, the clinical postural position was measured and electromyographic recordings (in seated and supine position, eyes open and eyes closed, before as well as 15 min after insertion of an occlusal splint) were from the anterior temporal and masseter muscles in thirty-one patients with signs and symptoms of mandibular dysfunction and nocturnal bruxism. The results indicated that when the patients were seated upright, there was a distinct postural activity in the anterior temporal and in some patients also in the masseter muscles. This postural activity decreased significantly with closure of the eyes and in supine position. Fifteen minutes after insertion of an occlusal splint, the postural activity in the temporal muscles decreased in 52%, increased in 22% and remained unchanged in 26% of the patients. Moreover, the postural activity reached its lowest level in supine position. The results indicate that the supine position is the body position to be preferred for centric relation recording as well as for occlusal and splint adjustment.

Adolescent↗
PubMed1991

Postural contractile activities of human jaw muscles following use of an occlusal splint.

As induced by an occlusal splint over a period of 1 week, this study monitored surface electromyographic changes in the postural contractile activities of jaw elevator and depressor muscles in six healthy adults. The immediate effect of the occlusal splint was to increase the postural contractile activities of the suprahyoid muscles. All postural muscle activities showed wide-ranging biological variation, but the activities induced by the splint tended to stabilize within 1 week, with decreased postural activities in the masseter and anterior temporalis muscles, and increased postural activities in the suprahyoid muscles.

Adult↗
PubMed2003

Role of mastication and swallowing in the control of autonomic nervous activity for heart rate in different postures.

Mastication and swallowing increase the heart rate, and posture change and respiration also modulate the heart rate. To clarify the role of mastication and swallowing in the modulation of the autonomic nervous activity, we investigated how they interact with modulation of the heart rate by changing body positions and respiration in young healthy subjects. R-R intervals of electrocardiogram at rest were significantly changed with different body positions, compared with supine and standing. A net shortening by mastication of a chewing gum base was similar in various postures. Respiration induced a periodic change in the R-R intervals, depending on the body postures, but mastication did not markedly change them in each posture. Dry swallowing at rest and spontaneous swallowing during the mastication in the sitting position induced a similar transient shortening and suppressed the respiration-induced changes after the swallowing. The net transient shortening by dry swallowing at rest was similar in the different postures. These results suggest that signals from mastication and swallowing are summated with those from body positions and respiration for shortening the R-R intervals and that signals from swallowing suppress the respiration-induced periodic changes.

Adult↗
PubMed1996

The effect of continuous epidural infusion of ropivacaine (0.1%, 0.2% and 0.3%) on nerve conduction velocity and postural control in volunteers.

BACKGROUND: Continuous epidural infusions of local anaesthetics have become increasingly popular in postoperative pain treatment, especially as they permit early mobilisation. Ropivacaine is a promising new agent which induces more pronounced sensory than motor blockade. This study was focused on the influence of continuous epidural infusion of ropivacaine on impulse conduction in large nerves (by measurement of F and H latencies), and on the subjects' ability to maintain postural control during mobilisation. METHODS: Healthy male volunteers received 0.1%, 0.2% or 0.3% ropivacaine, and bupivacaine 0.25% was used as reference. A bolus epidural injection of 10 ml of the drug, at L2/3 level, was followed by continuous infusion at 10 ml/h for 21 h. Motor blockade was assessed by mechanical measurements of force during big toe flexion and by recording of F latency. Sensory blockade was monitored by pin-prick and Thermotest methods, and by H latency recording. The subjects' ability to perform a postural test was evaluated by posturography. RESULTS: The F and H latencies became prolonged/abolished dose-dependently. With ropivacaine, F latency recovered significantly later than motor function (P = 0.0002), and H latency recovered later than normal pin-prick perception (P = 0.0006). However, the duration of partial blockade of thermoperception was comparable to that of H latency prolongation. Posturographically, the subjects receiving 0.1% ropivacaine differed significantly from all others (P < 0.001) in that they were able to maintain postural control during the infusion. The recovery period after termination of infusion was significantly shorter with ropivacaine than with bupivacaine for all measured variables. CONCLUSION: Recovery of postural control with 0.2% and 0.3% ropivacaine is significantly faster than with bupivacaine 0.25%. H latency recording allows detection of epidural blockade intensity that does not prevent subjects from performing postural tests.

Adult↗
PubMed2005

Postural stability of Parkinson's disease patients is improved by decreasing rigidity.

Postural instability has a big impact on the quality of life of patients with Parkinson's disease (PD) as it often leads to an insecure stance and fall. We investigated if postural stability in these patients improves by decreasing rigidity with a dopaminergic agonist. In our study, we tested eight PD patients with no concomitant diseases. Their age was 61 +/- 2 years (mean +/- SE) and their Hoehn-Yahr score was 3 +/- 0.1. The patients were evaluated according to the Unified Parkinson's Disease Rating Scale for motor function (mUPDRS) and with stabilometric measurements of forward-backward and side-to-side body oscillations during free stance with eyes open. Both evaluations were performed in an "off "state and in an apomorphine-induced "on" state. As expected, the mUPDRS score was significantly decreased in the "on" state with posture being improved in six patients, gait in eight patients and postural stability in seven of eight patients. In addition, apomorphine caused a significant reduction of the relative amplitude of lower frequencies and an increase of the relative amplitude of higher frequencies of forward-backward body oscillations. The results of stabilometry and mUPDRS evaluations are in agreement with the effect of apomorphine on rigidity, indicating that postural stability of PD patients is improved by decreasing rigidity.

Antiparkinson Agents↗
PubMed2001

Foot sole and ankle muscle inputs contribute jointly to human erect posture regulation.

In order to assess the relative contribution and the interactions of the plantar cutaneous and muscle proprioceptive feedback in controlling human erect posture, single or combined vibratory stimuli were applied to the forefoot areas and to the tendons of the tibialis anterior muscles of nine standing subjects using various vibration frequency patterns (ranging from 20 to 80 Hz). The variations in the centre of foot pressure, ankle angle and the EMG activities of the soleus and tibialis anterior muscles of each subject were recorded and analysed. Separate stimulation of the plantar forefoot zones or the tibialis anterior muscles always resulted in whole-body tilts oppositely directed backwards and forwards, respectively, the amplitude of which was proportional to the vibration frequency. EMG activity of ankle muscles also varied according to the direction of the postural responses. However, the same vibration frequency did not elicit equivalent postural responses: in the low frequency range, tactile stimulation induced stronger postural effects than proprioceptive stimulation, and the converse was the case for the higher frequency range. Under sensory conflict conditions, i.e. foot sole-flexor ankle muscle co-stimulation, the direction of the body tilts also varied according to the difference and the absolute levels of the vibration frequencies. In all cases, the resulting postural shifts always corresponded to the theoretical sum of the isolated effects observed upon vibrating each of these two sensory channels. We proposed that tactile and proprioceptive information from the foot soles and flexor ankle muscles might be co-processed following a vector addition mode to subserve the maintenance of erect stance in a complementary way.

Adult↗
PubMed1990

A longitudinal study of early leg postures of preterm infants.

The prone and supine resting postures of the pelvis and legs of 106 preterm infants (25 to 34 weeks gestation) were studied longitudinally between 30 and 38 weeks post-menstrual age. All the infants subsequently had normal motor development. Posture was graded in relation to three items: the angle of elevation of the pelvis and the weight-bearing surface of the knee in prone, and the angle of rotation of the leg in supine. Although no grade was found to be exclusive to a particular postmenstrual age, all three items showed a statistically significant progressive trend. Only less than 6 per cent of the infants regressed in grade during the study. Infants dependent on oxygen for more than 28 days had significantly lower grades for leg posture in both prone and supine. Posture was not significantly altered by time ex utero or by intra-uterine growth retardation. The results show that these observation items are suitable measures of the progressive development of antigravity postures of preterm infants.

Gestational Age↗
PubMed1995

Effect of early lead exposure on children's postural balance.

This study investigated the effect of chronic exposure to lead on children's ability to maintain upright postural balance as a biological marker of lead-induced modifications of the neuromotor system. For this study, 162 six-year-old children, with a five-year geometric mean lead concentration in blood of 11.9 micrograms/dL (range 4.0-28.0 micrograms/dL), were tested for postural balance with a microprocessor-based force platform system. An increase in blood lead was significantly associated with an increase in the variable postural sway--implying poorer postural balance. This association was not influenced by socio-economic, racial or environmental factors. This simple, objective and quick technique may be useful for assessing gross motor functions in children who are at or below the United States Centers for Disease Control's class III category and/or for monitoring the effectiveness of medical interventions aimed at reversing lead-associated impairment of upright postural balance.

Child↗
PubMed1993

Postural stability of hemodynamic responses during mental challenge.

Laboratory stress testing is typically conducted while subjects are seated, whereas real-life stressors may often be encountered while standing. The present study of 20 healthy young men evaluated blood pressure and underlying hemodynamic adjustments to a standardized mental arithmetic task performed twice while seated and twice while standing. Blood pressure increased during mental arithmetic in both postures, but the underlying hemodynamic determinants of the pressor responses were different for the two postures. Augmented cardiac output was responsible for increasing blood pressure during seated task performance, whereas increased vascular resistance was the mechanism for the pressor response to the task performed while standing. Blood pressure and hemodynamic responses were reproducible subject characteristics for a given posture; test-retest correlations were significant for all cardiovascular measures. However, seated blood pressures responses were not significantly correlated with standing blood pressure responses. In contrast, significant between-posture correlations were found for cardiac output and vascular resistance responses. This preliminary evidence of postural stability of the hemodynamic determinants of blood pressure responses during stress is consistent with growing evidence that hemodynamic response tendencies are robust characteristics of reactivity. Ambulatory monitoring of hemodynamic response patterns during real-life stress may reveal more idiosyncratic profiles of stress reactivity than are displayed by blood pressure responses alone.

Adult↗
PubMed1977

Ictal tonic postural changes and automatisms of the upper limb during epileptic parietal lobe discharges.

Tonic postural changes of the upper limb accompanied by epileptic parietal lobe discharges are not well known. The authors report 3 such cases. In the 3 patients, a total of 18 spontaneous seizures were recorded, 12 by telemetry, from either scalp electrodes or stereotactically implanted electrodes. Of these 18 seizures, 14 included tonic postural changes of the upper limb accompanied by a contralateral parietal discharge. Combining these 3 cases with the 4 such cases in the literature, the authors found that the clinical pattern consisted of a tonic postural change in one upper limb associated with automatisms of the opposite upper limb. It was also found that the same patient might have automatisms involving the upper limb in some seizures and upper limb postural changes in other seizures, both accompanied by the same electrical discharge. It is concluded that tonic postural changes and automatisms in the upper limb may be interchangeable.

Adult↗
PubMed1996

Dependence of atrial sensing function on posture in a single-lead atrial triggered ventricular (VDD) pacemaker.

The influence of body posture on atrial sensing was examined in a single-lead VDD pacemaker in 16 patients. At implantation, a position was searched for the floating atrial bipolar sensor to obtain an adequate atrial signal amplitude. After 1-12 months the atrial signals were measured by programming the sensitivity in five postures: supine, sitting, and standing and lying on the right and left sides. The group mean amplitudes of the atrial signal were equal in all postures, and comparable to the supine value (1.01 +/- 0.51 mV). However, the values within each individual varied considerably according to position, by a range of 0.46 +/- 0.41 mV on average. Testing only supine did not always predict decent sensing when upright, e.g., in 3 patients the atrial signal decreased more than 0.5 mV. In 24-hour ambulatory electrocardiography, with the sensitivity (0.15-0.30 mV) set to cover all postures, atrial beats were undersensed not at all in 4 patients, < 0.01% in 6 patients, and < 0.1% in the remaining 6 patients. Thus, with a floating atrial electrode, sensitivity testing in various postures is advisable to ascertain proper sensing function.

Aged↗
PubMed1998

Modulation of plasma melatonin concentrations by changes in posture.

Posture change from a lying position to a standing position results in a decrease in plasma volume, which leads to an increase in plasma constituents, especially that of proteins and blood constituents bound to them. The aim of the present study was to investigate the physiological effects of postural changes on plasma nocturnal melatonin concentrations in healthy human volunteers. The study was divided into four stages. During stage one, subjects were seated from 21.00 hr to 01.00 hr. In stage two, subjects were lying at ground level from 21.00 hr to 01.00 hr. In stage three, subjects were is a sitting position from 2100 hr to 2300 hr and then in a standing position from 23.00 hr to 24.00 hr, and back to the sitting position from 24.00 hr to 01.00 hr. In the final stage, subjects were in a lying position from 21.00 hr to 23.00 hr and then in a standing position from 23.00 hr to 24.00 hr and back to the lying position from 24.00 hr to 01.00 hr. AUC analysis showed significant differences between sitting and lying positions (t=2.84; P<0.05; df=5), with higher melatonin levels associated with the sitting position (mean difference in peak concentration of 17.1 pg/ml). Furthermore a change in posture from the lying to the standing position produced a statistically significant increase in melatonin concentrations (final stage) (t=-3.37; P<0.05; df=5) (mean difference in peak concentration of 28.5 pg/ml). No differences were found with a change in posture from a sitting to a standing position. The hemoconcentration and hemodilution associated with posture changes may play a role in altering plasma protein bound hormones such as melatonin.

Adult↗
PubMed2006

Effect of expertise and visual contribution on postural control in soccer.

This work analyzes the postural performance and the use of visual information in soccer players according to their level of competition. Two groups of healthy soccer players were investigated at the mid-competition season: an amateur (AM) (n=15) group composed of regional-level players and a professional group at a national level (PRO) (n=15). Posture was assessed by measuring the center of foot pressure (COP) with a force platform during a test (51.2 s) of bipedal quiet standing posture. The test was completed with eyes open (the subjects looked at a fixed-level target at a distance of 2 m) and closed (they kept their gaze in a straight-ahead direction). The statistical analysis showed that PRO soccer players were more stable than AM soccer players. Moreover, the contribution of vision in postural maintenance was less important in the PRO players than in the AM players. The present study suggests that intense training allows PRO soccer players to become less dependent on vision to control their posture such that vision can be dedicated to treating the information, that emanates from the game.

Adolescent↗
PubMed1991

Plasma atrial natriuretic peptide and vasopressin during thermal dehydration in supine posture.

After 30 minutes spent in an upright posture six healthy male subjects underwent two 130-minute experiments in a supine posture, the first in thermoneutral conditions (TC) and the second, 15 days later, in a hot environment (HE) in order to obtain a water loss of 2.5% body weight. In thermoneutral conditions, the supine posture induced plasma volume expansion, resulting in slightly lowered plasma vasopressin (AVP) levels and higher plasma atrial natriuretic peptide (ANP) levels, compared to the values obtained in the upright posture (P less than 0.05). During hot environment, the sweating-induced dehydration led to a significant reduction of plasma volume expansion and to an increase in rectal temperature and plasma osmolality (P less than 0.05). Plasma vasopressin levels were higher at the end of the heat exposure (P less than 0.05) but natriuretic peptide levels did not change, compared to the values observed in the upright posture. These data suggest that plasma volume reduction induced by thermal dehydration may limit the natriuretic peptide release, which occurs after changing from the upright to a supine position.

Adult↗
PubMed1974

Modification of the postural response of the normal dog by blindfolding.

1. Normal dogs were trained to stand quietly upon a movable platform. The animals' postural adjustments in response to sinusoidal motion of the platform were assessed in both the normal and the blindfolded condition. The induced postural adjustments were described by the Fourier coefficients for the fundamental of the input together with the coefficients which were integral multiples of the fundamental.2. All of the output variables, including motion at the hind limb joints and of the body, showed modifications when the dogs were blindfolded. The body motion increased in amplitude, as measured by the fundamental Fourier coefficient, and further lagged the input motion. Motion at the knee and phalangeal joints also increased in amplitude and the timing of these movements shifted from the normal in characteristic patterns for different frequencies of input motion.3. The modifications of the postural response due to blindfolding were most pronounced at the lower input frequencies: 0.2-1.0 Hz. At 1.4 Hz or above the fundamental coefficients of most of the output measures resembled those of the normal condition. Even at the higher input frequencies, however, the postural response of the blindfolded dog was more distorted than that of the normal dog.4. It is hypothesized that relatively slow movement of the visual surround provides the dog with information which is essential to normal operations of the postural control system.

Animals↗
PubMed1977

Postural effects on muscle nerve sympathetic activity in man.

1. Pulse-synchronous bursts of multi-unit sympathetic activity (MSA) were recorded in peroneal muscle nerve fascicles in eight healthy subjects when lying, sitting and standing. The sympathetic activity was quantitated by counting the number of bursts in the mean voltage neurogram/min. Postural changes were analysed by considering the total activity to be a product of the number of bursts in relation to the number of heart beats (burst incidence) and the heart rate.2. In lying there were large interindividual differences in total activity, but for all subjects the activity increased when going from lying to sitting and from sitting to standing. With a few exceptions the increase between the lying and sitting postures was associated with an increase in both burst incidence and heart rate whereas between the sitting and standing postures there was an increase in heart rate but on the average no change in burst incidence.3. When going from lying to sitting or from sitting to standing the magnitude of the change in burst incidence was inversely related to the initial burst incidence so that subjects with low initial values usually showed greater increases in burst incidence than subjects with high initial values. Some subjects with high initial values decreased their burst incidence.4. With changes in postures there was an inverse linear relationship between the fraction of the change in MSA associated with a change in burst incidence and the fraction associated with a change in heart rate. An increase in total activity could be obtained by changing only burst incidence, by increasing heart rate without changing burst incidence, or by appropriate changes in both parameters. The slope of the regression line was -0.53 indicating that for adequate postural compensation fewer additional bursts were required when the compensatory response involved an increase in heart rate rather than an increase in only burst incidence.5. It is suggested that an impairment of the ability to regulate heart rate will make subjects with high burst incidence in the lying position orthostatically more vulnerable than those with low burst incidence.6. Shortly after standing up one subject developed bradycardia and subsequently fainted. The nerve recording was maintained until the subject collapsed. During the initial bradycardia no sympathetic bursts occurred suggesting that the syncope was associated with an interruption of normal baroreflex feedback between blood pressure and sympathetic outflow.

Adult↗
PubMed1996

Effects of body immersion on postural adjustments to voluntary arm movements in humans: role of load receptor input.

1. The effect of body immersion on postural adjustments was studied in ten healthy subjects. Reaction times, for pushing or pulling a rigid handle, in response to a visual stimulus were measured. In addition EMG recordings were taken from upper arm and lower leg muscles during three levels of body immersion while standing on a platform (immersed to spinal levels: lumbar nerve root 2 (L2); thoracic nerve root 4 (T4); and cervical nerve root 7 (C7)), while floating and while standing or sitting out of water. 2. With increasing levels of body immersion there was a near linear reduction in the amplitude of the gastrocnemius (GM) EMG activity before (200 ms) the onset of a force signal from pulling, but immersion had a significantly weaker effect on the amplitude of the tibialis anterior (TA) EMG during pushing movements. There was no significant difference in the effect of body immersion on biceps femoris (BF) and rectus femoris (RF). Under free-floating conditions postural adjustments did not occur in response to pull or push movements. There were no adaptational changes of EMG adjustments during successive trials at a given immersion level. 3. Under non-immersed conditions reaction times were significantly shorter during sitting than during standing. This difference is assumed to be due to the postural adjustments required while standing before the onset of a voluntary arm movement. While standing, reaction times were significantly longer for pull compared with push movements. Under all conditions of body immersion the reaction times remained longer compared with the sitting condition, even when no leg muscle EMG adjustments were present. 4. It is assumed that the differential effect of body immersion on the antagonistic leg muscles is due to the differential neuronal control of antagonistic leg muscles with a strong influence from proprioceptive input (most probably from load receptors) on the leg extensors. The longer reaction times seen during body immersion, where no postural adjustments were evident, suggests that a supraspinal command to the leg muscles precedes the voluntary arm movement. However, because of the changed/decreased afferent input no postural adjustments are generated.

Arm↗