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PubMed1996

Effect of posture on hip joint moment during pregnancy, while performing a standing task.

In this paper the combined effect on reactive hip joint moment due to changes in (1) segment mass, (2) trunk centre of mass, and (3) working posture during pregnancy was estimated, and the relative contributions of these three changes to the change in the moment were assessed. The situation studied concerned standing work at a table. Sixteen women were studied monthly during pregnancy. The working posture was assessed by two-dimensional photographic posture recording and description. Body dimensions were measured to assess segment characteristics. A two-dimensional static model was used to estimate the reactive hip joint moment at 10, 20, 30 and 40 weeks of pregnancy. Between 10 and 40 weeks of pregnancy the moment increase was 52 Nm, i.e. the load at 40 weeks of pregnancy is 2.8 times the load at 10 weeks of pregnancy. On average half of this increase was due to postural changes. Changes in segment mass, trunk centre of mass, and the interaction between the three changes accounted for rougly 10, 20 and 15% of the load increase respectively. The increase in reactive hip joint moment may be minimized by preventing adverse postural changes, and optimizing the posture to reduce the contribution of changes in body weight (distribution).

Journal Article↗
PubMed1995

Exercise, posture, and back pain during pregnancy.

One of the expected benefits of exercise programmes for pregnant women is to reduce or prevent back pain by improving posture. The aim of this project was to evaluate the effect of fitness classes for pregnant women on posture and back pain. In this article, postural aspects are reported. Sixty five pregnant volunteers were included in the study, of whom 27 were enrolled in exercise classes designed according to Canadian guidelines and 38 acted as sedentary controls. Posture was assessed every 4 weeks during pregnancy and 4 months postpartum by measuring curvatures of the lumbar and thoracic spines in a standard relaxed standing position from lateral photographs. Laxity of knee ligaments was also monitored using a clinical arthrometer. Weight gain could explain part of lordosis increase during pregnancy but the effect was not very strong. No effect of exercise on posture was detected. RELEVANCE: This study showed that fitness classes for pregnant women designed according to Canadian guidelines had no detectable effect on posture during pregnancy.

Journal Article↗
PubMed2006

Age-related part taken by attentional cognitive processes in standing postural control in a dual-task context.

The aim of this work was to determine the effects of ageing on the possible mobilisation of cognitive processes in orthostatic postural balance. Seventy-nine individuals of three different age groups were placed in dual-task situations that combined standing postural control with three different cognitive tasks. Two of these three tasks, auditory-verbal and visual-verbal ones, required external information acquisition whereas the third, a mental counting task, did not require such information. The results showed contrasting variations in postural control performances that are an improvement in young subjects during cognitive tasks which required external information acquisition and a deterioration in elderly subjects during cognitive tasks which did not involve external information acquisition. The middle-aged subjects tended to develop these two types of variations simultaneously. These results confirm that cognitive processes could have a role that increases with age in ensuring postural control. The contrasting results observed between the young and old populations highlight that the allocation of cognitive resources to postural control could, on the one hand, contribute to improving postural performance in subjects with mainly automated control and, on the other, perturb this performance in subjects with mainly cognitive control.

Adult↗
PubMed2006

Moderate alterations in lower limbs muscle temperature do not affect postural stability during quiet standing in both young and older women.

Older adults demonstrate increased amounts of postural sway, which may ultimately lead to falls. Temperature is known to have a profound effect on the performance of the neuromuscular system which could have important implications on motor control. It is, therefore, of interest to investigate if the age-related decline in postural stability could be affected by changes in local limbs temperature. The present study investigated the effects of localized warming and cooling on postural sway in nine young (22+/-3 years) and nine older (73+/-3 years) women. Postural sway was assessed, using a single force platform, during quiet standing at three muscle temperature conditions: control (34.2+/-0.2 degrees C), cold (31.3+/-0.3 degrees C) and warm (37.0+/-0.1 degrees C). Two stances were evaluated, the Romberg (large support base) and modified Tandem (narrow support base), under both eyes-open and eyes-closed conditions. Root mean square (RMS), mean velocity (MV), sway area (SA) and mean power frequency (MPF) were calculated from the centre of pressure (COP) displacement. Neither warming nor cooling significantly affected any of the postural parameters which were, however, all higher (P<0.05) in the older group than the young group in all conditions. This study demonstrated that, in quiet standing conditions, a moderate variation (+/-3 degrees C) in lower limbs temperature does not affect postural steadiness in either young or older women.

Adult↗
PubMed2001

[Postural tremor: clinical and neurophysiological study in a consecutive series of 300 patients].

BACKGROUND: There are few studies analysing the clinical and neurophysiological characteristics of postural tremor in Spain. PATIENTS AND METHOD: We studied prospectively 300 consecutive patients referred to a Movement Disorders Section because of postural tremor of the upper limbs. Syndromic diagnosis of postural tremor was made according to clinical criteria with the aid of neurophysiological criteria (accelerometric and EMG data). In patients diagnosed with essential tremor (ET), diagnostic sensitivity studies, correlation studies of clinical and neurophysiological data and multivariate analysis were performed. RESULTS: Most frequent syndromic diagnoses were ET (77%), parkinsonian postural tremor (10%) and exaggerated physiological tremor (6%). Fifty percent of ET patients reported having affected relatives, and 7% reported that their tremor improved with alcohol. Mostly specific variables for the diagnosis of ET were: affected relatives (77%), cephalic tremor (80%), alcohol improvement (100%), and synchronous EMG pattern (79%). The presence of affected relatives and a synchronous EMG pattern were significant predictive variables on a multivariate analysis. We found a significant correlation between age at time of consulting and frequency (rs = 0.561; p < 0.0005) and amplitude (rs = 0.470; p < 0.0005) of tremor. CONCLUSIONS: In the present study, ET was the most common cause of reference for postural tremor. Selective clinical data and neurophysiological evaluation are useful for the diagnosis of postural tremor.

Aged↗
PubMed2001

Peri-partum posture and behaviour of gilts and the location of their piglets in lines selected for components of efficient lean growth.

Peri-partum posture and behaviour of gilts from lines selected for different components of efficient lean growth were studied to determine if behavioural changes may have been associated with the observed responses in reproductive performance. The proportions of time that gilts expressed defined posture and behaviour traits and the locations of their piglets were determined from video recordings of observations made at 5min intervals in the period extending from 2h pre-farrowing to 2h post-farrowing. The 137 gilts studied were from four pairs of Large White lines which had been divergently (high and low) selected for either daily food intake (DFI), lean food conversion efficiency (LFC), lean growth rate on ad libitum feeding (LGA) or lean growth rate on a restricted feeding scale (LGS).Almost all the significant (P<05) changes occurred in the LGS pair of lines. In the pre-farrowing period, relative to the low LGS gilts, high LGS gilts spent a higher proportion of their time lying on their sides (0.92 versus 0.69), and less time in the upright postures of standing, sitting or lying on their bellies (0.08 versus 0.33) and engaging in nesting behaviour (0.02 versus 0.10). During farrowing, high LGS gilts again lay on their sides more often than low LGS gilts (0.96 versus 0.80) and were upright less often (0.04 versus 0.20). High LGS gilts changed posture less often than low LGS gilts (0.05 versus 0.31) but were more often alert (0.79 versus 0.61). During farrowing, high LGS piglets were seen less often at their mother's head, back and vulva or at the creep than low LGS piglets (0.06 versus 0.15). Post-farrowing, there were no significant differences between the lines, almost all gilts lying on their sides with their piglets at the udder. Divergent selection for components of efficient lean growth rate on ad libitum feeding was not associated with consistent responses in gilt posture and behaviour or in piglet location. Selection for high lean growth on restricted feeding had effects on gilt posture and behaviour which may have been beneficial to her welfare and that of her piglets.

Journal Article↗
PubMed1997

Anticipatory postural adjustments during standing in below-the-knee amputees.

OBJECTIVE: We studied the role of adaptive changes within the central nervous system in anticipatory postural adjustments seen in unilateral below-the-knee amputees. DESIGN: Changes in electromyographic and mechanical variables were compared during standardized tasks performed by standing subjects. BACKGROUND: Anticipatory postural adjustments represent an important mechanism of postural control which was expected to be changed in amputees because of both mechanical and secondary, neurological reasons. METHODS: Six patients after a below-the-knee amputation and six control subjects stood on a force platform and performed fast bilateral shoulder movements and also dropped or caught a load from (into) extended hands. Anticipatory changes in the background activity of postural muscles were analysed. RESULTS: In amputees, there were cases of marked asymmetry in anticipatory changes of the background muscle activity which were larger on the intact side of the body but were commonly small or absent on the side of the amputation. This asymmetry could lead to larger mediolateral forces and displacements of the centre of pressure. CONCLUSIONS: We suggest that asymmetrical patterns of anticipatory postural adjustments reflect central adaptive changes secondary to the amputation. Rehabilitation approaches would benefit from understanding and taking advantage of the adaptive changes within the central nervous system. RELEVANCE: We demonstrated asymmetries in patterns of anticipatory postural adjustments during voluntary arm movements and load manipulations by standing unilateral amputees. This finding is of potential importance for rehabilitation of amputees and their prosthetic training.

Journal Article↗
PubMed1996

Longitudinal Development of the Automatic Postural Response in Infants.

In this longitudinal study, the development of automatic postural responses elicited during stance following perturbation of the support surface was investigated. Infants (N = 9) unable to stand without support were tested initially: follow-up tests were performed until the infants were able to stand and walk independently. Surface electromyographic recordings of leg and trunk muscle activity following a postural perturbation induced by a forward or backward translation of the support surface were made for each infant. Muscle onset latencies following the perturbation and the proportion of trials in which muscle activity was recorded were determined. First, infants activated appropriate muscles either in isolation or in pairs and then combined these muscles into functional synergies. Although activation of all three postural muscles was recorded in infants before they were able to stand and walk independently, the three-muscle response was not consistent in the youngest children. The proportion of trials eliciting muscle activity continued to increase (p <.O5) after infants began to walk independently, with postural muscle activity recorded in virtually every trial by late independent walking. Thus. the automatic postural response elicited during stance was shown to begin with activity in single or paired muscles, followed by activation of the postural muscles in functional synergies. These data illustrate the progressive development of an effective sensory-motor organization.

Journal Article↗
PubMed2004

Effects of subthalamic nucleus stimulation and medication on resting and postural tremor in Parkinson's disease.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) and antiparkinsonian medication have proved to be effective treatments for tremor in Parkinson's disease. To date it is not known how and to what extent STN DBS alone and in combination with antiparkinsonian medication alters the pathophysiology of resting and postural tremor in idiopathic Parkinson's disease. The purpose of this study was to examine the effects of STN DBS and antiparkinsonian medication on the neurophysiological characteristics of resting and postural hand tremor in Parkinson's disease. Resting and postural hand tremor were recorded using accelerometry and surface electromyography (EMG) from 10 Parkinson's disease patients and 10 matched control subjects. The Parkinson's disease subjects were examined under four treatment conditions: (i) off treatment; (ii) STN DBS; (iii) medication; and (iv) medication plus STN DBS. The amplitude, EMG frequency, regularity, and 1-8 Hz tremor-EMG coherence were analysed. Both STN DBS and medication reduced the amplitude, regularity and tremor-EMG coherence, and increased the EMG frequency of resting and postural tremor in Parkinson's disease. STN DBS was more effective than medication in reducing the amplitude and increasing the frequency of resting and postural tremor to healthy physiological levels. These findings provide strong evidence that effective STN DBS normalizes the amplitude and frequency of tremor. The findings suggest that neural activity in the STN is an important modulator of the neural network(s) responsible for both resting and postural tremor genesis in Parkinson's disease.

Adult↗
PubMed1995

The role of potassium in postural hypotension: electrolytes and neurohumoral factors in elderly hypertensive patients using diuretics.

OBJECTIVE: To study the association between postural hypotension and (i) electrolyte levels and (ii) neurohumoral factors in elderly hypertensive patients using diuretics. DESIGN: Cross-sectional study of patients and controls. SETTING: The subjects were gathered from senior citizen clubs or they were referred to the study by general practitioners. The subjects were examined on a geriatric ward in Turku City Hospital. SUBJECTS: Seven subjects with postural hypotension and 13 controls. MEASUREMENTS: Plasma electrolyte levels and neurohumoral response to head-up tilt. RESULTS: There were significantly more hypokalaemic subjects in the postural hypotension group (5/7) than in the control group (1/13) (P < 0.01). The plasma potassium level was negatively correlated to plasma aldosterone (r = -0.57; P < 0.01) and renin activity (r = -0.69; P < 0.001). Subjects with postural hypotension had higher levels of noradrenaline, both supine (P < 0.05) and during tilt (P < 0.05). There were no significant differences in supine or tilt levels of plasma adrenaline, vasopressin, atrial natriuretic peptide, aldosterone and renin activity between the groups. CONCLUSION: The results suggest that potassium depletion is associated with postural hypotension in elderly hypertensive patients using diuretics. However, it is unclear whether there is a causative link between potassium depletion and postural hypotension or whether they are both caused by some other factor, e.g. volume contraction.

Aged↗
PubMed2004

Postural hand tremor before and following liver transplantation and immunosuppression with cyclosporine or tacrolimus in patients without clinical signs of hepatic encephalopathy.

OBJECTIVE: To assess tremor characteristics and severity in patients with severe liver disease without hepatic encephalopathy and following orthotopic liver transplantation (LTX) and immunosuppression (IS) with cyclosporin A (CsA) or tacrolimus (FK 506). METHODS: A total of 35 consecutive patients were included into the prospective study and serum levels of CsA (n = 29) or FK 506 (n = 6) were monitored following LTX. Tremor characteristics and severity were assessed by two-blinded raters before and following LTX. In addition, accelerometric recordings were taken before and after LTX, and compared with 16 normal controls without tremor and without clinical signs of hepatic encephalopathy or liver disease. Accelerometry was performed while sitting in a comfortable chair with the forearms supported and included rest and postural condition with and without weight load (500 g) on each hand. Kolmogorov-Smirnov test, paired t-test and t-test for independent samples were used for statistical analysis. RESULTS: The clinical rating revealed no rest but a mild postural hand tremor before LTX with a significant increase following LTX (p < 0.001). After LTX the mean score of postural tremor was significantly (p < 0.05) higher in patients with plasma levels of >850 ng CsA/ml compared with patients with lower levels. Patients and normal controls showed comparable mean peak frequencies of rest and postural hand tremor. The mean amplitude of postural hand tremor was significantly higher in patients before and after LTX compared with controls. In the majority of patients (89%) and controls (88%), the dominant tremor frequency decreased significantly (>1.5 Hz) when applying a weight load on each hand. CONCLUSION: The present study is the first to describe hand tremor characteristics in patients with severe liver disease without clinical signs of hepatic encephalopathy and in patients following LTX and IS. Compared with normal controls the patients showed a significant postural hand tremor prior and post-LTX and an increase of mean tremor amplitude following LTX and CsA/FK 506 treatment. The decrease of the dominant tremor frequency with weight load and an increase of tremor amplitude with higher plasma levels of CsA are both indicative of an enhanced physiological or toxic tremor.

Adult↗
PubMed1991

Correlates of postural hypotension in a community sample of elderly blacks and whites.

Postural hypotension is thought to be prevalent among the elderly, but few community-based studies of this condition have been conducted. In addition, little is known about postural hypotension in blacks despite well documented racial differences in hypertension and stroke. Data on 659 elderly (greater than or equal to 60 years of age) participants in a survey of two rural, biracial townships were analyzed to describe the frequency and correlates of postural hypotension. Twelve percent of the 659 adults experienced a drop of 10 mmHg or greater in systolic blood pressure on going from sitting to standing (supine measures were not available). This degree of postural hypotension was twice as common for whites as for blacks (14.5% vs 7.5%, P = 0.01). Postural hypotension was associated with elevated sitting blood pressure and showed positive but statistically non-significant relationships with anti-hypertensive medications and leanness. The association between race and postural hypotension persisted after adjusting for these and other risk factors (OR = 2.2, 95% CI:1.2,4.0).

Aged↗
PubMed1982

Postural and maximal activity in elevators of mandible before and after treatment of functional disorders.

In a longitudinal study we compared clinical data on pain and tenderness and electromyographic recordings of postural and maximal activity from 37 patients before and after treatment of functional disorders of the masticatory system. Forty-three dental students served as controls. Treatment was followed by a concomitant decrease of pain, tenderness and postural activity. Muscle strength in terms of the activity during maximal bite in the intercuspal position was not altered by treatment, but activation of the right and left anterior temporal muscles became more uniform. The relative postural loading of the elevators was assessed as their activity in percent of full effort. Following treatment, loading in patients decreased significantly and became more symmetrical in the anterior temporal muscles. Loading also tended to decrease in the posterior temporal and masseter muscles. However, it still significantly exceeded postural activity in percent of full effort in the controls. Since treatment involved correction of the occlusion we conclude that the intermaxillary conditions of tooth contact during function play a role in the etiology of functional disorders and that the reduction of the relative postural loading of the elevators of the patients due to this treatment contributed to their relief. The relatively high percentage of full effort displayed as postural activity by the patients even after treatment may explain fluctuation of symptoms and signs of functional disorders of the masticatory system. It also emphasizes the need for improved methods of treatment to reduce the probability of recurrence.

Adolescent↗
PubMed2003

Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans.

Patients with acute respiratory distress syndrome have increased lung tissue weight and therefore an increased hydrostatic pressure gradient down the lung. Also, they have a better arterial oxygenation in prone (face down) than in supine (face up) posture. We hypothesized that this effect of the direction of gravity also existed in healthy humans, when increased hydrostatic gradients were induced by hypergravity. Ten healthy subjects were studied in a human centrifuge while exposed to 1 or 5 G in anterio-posterior (supine) or posterio-anterior (prone) direction. We measured blood gases using remote-controlled sampling and gas exchange by mass spectrometry. Hypergravity led to marked impairments of arterial oxygenation in both postures and more so in supine posture. At 5 G, the arterial oxygen saturation was 84.6 +/- 1.2 % (mean +/- S.E.M.) in supine and 89.7 +/- 1.4 % in prone posture (P < 0.001 for supine vs. prone). Ventilation and alveolar PO2 were increased at 5 G and did not differ between postures. The alveolar-to-arterial PO2 difference increased at 5 G to 8.0 +/- 0.2 kPa and 6.6 +/- 0.3 kPa in supine and prone postures (P = 0.003). Arterial oxygenation was less impaired in prone during hypergravity due to a better-preserved alveolo-arterial oxygen transport. We speculate that mammals have developed a cardiopulmonary structure that favours function with the gravitational vector in the posterio-anterior direction.

Adult↗
PubMed2001

Phacovitrectomy without prone posture for full thickness macular holes.

AIMS: To investigate the role of phacovitrectomy surgery without prone posture for stage 2 and 3 macular holes. METHODS: A pilot study was performed on 20 patients (20 eyes) having phacoemulsification lens removal and vitrectomy surgery with 20% C(2)F(6) tamponade. Patients were advised to avoid lying on their backs for 10 days following surgery but no other posturing instructions were given. Closure rates and improvement in visual acuity were compared with a group of historical controls in whom phacovitrectomy with gas tamponade and face down posturing was performed. RESULTS: Anatomical hole closure was noted in 18 of the 20 eyes (90%). 19 eyes (95%) showed an improvement of at least 0.3 logMAR units. This compares favourably with the postured group in which anatomical hole closure was noted in 11 of 13 eyes (85%) and nine of 13 eyes (69%) showed an improvement of at least 0.3 logMAR units. CONCLUSION: Combined surgery facilitates the use of a large gas bubble. Sufficient tamponade of the hole occurs for closure without prone posturing. Combined surgery prevents patients posturing and returning for cataract surgery.

Aged↗
PubMed2001

Is postural hypotension a real problem with antihypertensive medication?

Historically, postural hypotension has been cited as a consideration which might influence the selection of antihypertensive therapy. The common symptoms (dizziness, blackouts, syncope) give cause for concern but they are not attributed to every class of antihypertensive drug. For example, administration of a beta-blocker is not generally associated with symptomatic postural hypotension, whereas the alpha-blocker prazosin was particularly problematical, with a significant and well-recognized risk of first-dose postural effects. Titration from a low starting dose and careful selection/monitoring of patients have been successfully used to circumvent this problem. However, since there is a relatively high incidence of postural hypotensive symptoms in elderly patients in general, it may be a misconception to attribute such symptoms to any particular type of antihypertensive drug. Furthermore, with the newer alpha(1)-blockers, such as doxazosin, which have a more gradual onset of action, there is a markedly reduced tendency for postural hypotension to occur. Thus, it is perhaps time to reassess the real significance of iatrogenic postural hypotension in the selection of antihypertensive therapy.

Aged↗
PubMed1998

Locomotion in alligator mississippiensis: kinematic effects of speed and posture and their relevance to the sprawling-to-erect paradigm

In terms of locomotory posture, amphibians and lizards are considered to be sprawlers, mammals and dinosaurs are considered to be erect, and extant crocodilians are considered to be intermediate because they use the 'high walk', a semi-erect posture where the body is held half-way between the sprawling and erect grades during locomotion. In addition, crocodilians occasionally use a sprawling posture. Extant crocodilians, therefore, provide an interesting model in which to investigate the sprawling-to-erect transition in vertebrate evolution. This study quantifies the sprawl and high walk kinematics of the alligator Alligator mississippiensis moving at different speeds on a treadmill and compares them with kinematic data available for other vertebrates. These data allow us to examine the effects of speed on crocodilian postures and to examine how crocodilian locomotion relates to the sprawling-to-erect paradigm in vertebrate locomotion. Our results show that the crocodilian sprawl is not functionally equivalent to the primitive sprawling behaviors exhibited by salamanders and lizards. In fact, although the high walks and sprawls of alligators exhibit some kinematic differences, they are actually much more similar than expected and, essentially, the crocodilian sprawl is a lower version of a high walk and could be termed a 'low walk'. In terms of the sprawling-to-erect transition, the high walk has knee kinematics intermediate between those of birds and non-archosaurian tetrapods, but alligators increase speed in a way completely different from other terrestrial vertebrates (distal rather than proximal limb elements are used to increase speed). These kinematic data viewed in the light of the fossil and phylogenetic evidence that modern crocodilians evolved from erect ancestors suggest that modern crocodilians have secondarily evolved a variable semi-erect posture and that they are problematic as an intermediate model for the evolutionary transition from sprawling to erect postures in archosaurs.

Journal Article↗
PubMedDate not supplied

Criterion validation of four criteria of the foot posture index.

The Foot Posture Index is a new multidimensional and multiplanar tool aimed at quantifying the degree of pronation to supination of the foot, comprising eight criteria that sum to produce a final "score" of foot posture. In an initial study involving 31 subjects, angulations measured from dorsoplantar and lateral radiographs were compared with the corresponding Foot Posture Index criteria using Spearman's rho and the generalized linear model of analysis of variance. Eleven of the participants from Study 1 completed a second study in which wedges were used to alter foot position to determine whether changes to foot position were sensitively reflected in Foot Posture Index criterion scores and associated radiographic images. Study 1 demonstrated a significant correlation for only one criterion (talar head palpation), while Study 2 demonstrated intrasubject sensitivity to overall changes from supinated to pronated and supinated to resting positions but insensitivity to changes from resting to pronated positions. The results suggest that although the Foot Posture Index could be a useful tool to broadly classify foot postures, it is not sensitive to all small movements when assessed by this method.

Adult↗