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PubMed2005

Development of postural control in healthy children: a functional approach.

From a set of experimental studies showing how intersegmental coordination develops during childhood in various posturokinetic tasks, we have established a repertoire of equilibrium strategies in the course of ontogenesis. The experimental data demonstrate that the first reference frame used for the organization of balance control during locomotion is the pelvis, especially in young children. Head stabilization during posturokinetic activities, particularly locomotion, constitutes a complex motor skill requiring a long time to develop during childhood. When studying the emergence of postural strategies, it is essential to distinguish between results that can be explained by biomechanical reasons strictly and those reflecting the maturation of the central nervous system (CNS). To address this problem, we have studied our young subjects in situations requiring various types of adaptation. The studies dealing with adaptation of postural strategies aimed at testing short and long-term adaptation capacity of the CNS during imposed transient external biomechanical constraints in healthy children, and during chronic internal constraints in children with skeletal pathologies. In addition to maintenance of balance, another function of posture is to ensure the orientation of a body segment. It appears that the control of orientation and the control of balance both require the trunk as an initial reference frame involving a development from egocentric to exocentric postural control. It is concluded that the first step for children consists in building a repertoire of postural strategies, and the second step consists in learning to select the most appropriate postural strategy, depending on the ability to anticipate the consequence of the movement in order to maintain balance control and the efficiency of the task.

Adaptation, Physiological↗
PubMed2005

Development of postural muscles and their innervation.

Control of posture is a prerequisite for efficient motor performance. Posture depends on muscles capable of enduring contractions, whereas movements often require quick, forceful muscle actions. To serve these different goals, muscles contain fibers that meet these different tasks. Muscles with strong postural functions mainly consist of slow muscle fibers with a great resistance against fatigue. Flexor muscles in the leg and arm muscles are mainly composed of fast muscle fibers producing relatively large forces that are rapidly fatigable. Development of the neuromuscular system continues after birth. We discuss in the human baby and in animal experiments changes in muscle fiber properties, regression from polyneural into mononeural innervation, and developmental changes in the motoneurons of postural muscles during that period. The regression of poly-neural innervation in postural muscles and the development of dendrite bundles of their motoneurons seem to be linked to the transition from the immature into the adult-like patterns of moving and postural control.

Animals↗
PubMed2005

Postural control in man: the phylogenetic perspective.

Erect posture in man is a recent affordance from an evolutionary perspective. About eight million years ago, the stock from which modern humans derived split off from the ape family, and from around sixty-thousand years ago, modern man developed. Upright gait and manipulations while standing pose intricate cybernetic problems for postural control. The trunk, having an older evolutionary history than the extremities, is innervated by medially descending motor systems and extremity muscles by the more recent, laterally descending systems. Movements obviously require concerted actions from both systems. Research in rats has demonstrated the interdependencies between postural control and the development of fluent walking. Only 15 days after birth, adult-like fluent locomotion emerges and is critically dependent upon postural development. Vesttibular deprivation induces a retardation in postural development and, consequently, a retarded development of adult-like locomotion. The cerebellum obviously has an important role in mutual adjustments in postural control and extremity movements, or, in coupling the phylogenetic older and newer structures. In the human, the cerebellum develops partly after birth and therefore is vulnerable to adverse perinatal influences. Such vulnerability seems to justify focusing our scientific research efforts onto the development of this structure.

Animals↗
PubMedDate not supplied

Interaction between attention demanding motor and cognitive tasks and static postural stability.

BACKGROUND: Due to the often-reported decrease in postural stability in the elderly, it is important to understand factors that may contribute to reduced postural stability. It is possible that attention-demanding focal tasks performed concurrent with postural regulation influence postural stability. OBJECTIVE: This study utilized dual-task methodology to determine if motor or cognitive focal tasks interact with center of pressure (COP) excursion during static bipedal stance in healthy young and healthy elderly subjects (n = 18). METHODS: The cognitive task involved silently solving an orally-presented multi-step arithmetic problem over a 30-second period. The motor task was a 30-second bilateral static finger-thumb pinch task performed at 10% of maximal voluntary contraction with a pair of pinch-force transducers. Each focal task was performed separately, and in a condition in which both tasks were performed simultaneously. COP excursion was compared in quiet standing (no focal task) and during performance of the focal tasks with full vision and with vision occluded. RESULTS: Performance on the focal tasks was unaffected by increased postural demands during stance as compared to a seated baseline condition. This was the case for both age groups, and for the full vision and occluded vision conditions. Medio-lateral COP excursion was reduced over the quiet standing pretest condition when attentional focus was on the cognitive task, suggesting that COP was influenced centrally during cognition. In contrast, COP excursion increased over the quiet standing pretest condition when performing the motor focal task, suggesting a reduced ability to suppress sway when the motor system was concurrently occupied with a voluntary task that shared the same input-output resources. CONCLUSION: The ability to share attentional resources among focal and postural tasks was similar in healthy young and elderly subjects.

Adult↗
PubMedDate not supplied

Effects of regular walking on postural stability in the elderly.

BACKGROUND: Both age and lack of physical activity may be responsible for poor health and poor balance control. Conversely, physical activity may modulate postural control in elderly people. OBJECTIVE: An observational study was performed in older adults to explore whether walking on a regular basis might prove to be beneficial not only to the cardiovascular system but also to maintaining a good balance. METHODS: Twenty-two healthy older subjects walking on a regular basis (DW group) and 121 healthy control older subjects who did not walk regularly (NW group) were studied. The subjects included in the study were free from major gait and postural disorders. An instrumented force platform was used to measure the time-varying displacements of the center of pressure under eight static conditions and postural limit tests. An isometric test was performed to evaluate lower limb muscle strength, and a static two-point discrimination test evaluated the innervation density of the slowly adapting receptors of the sole of the first toe. RESULTS: The DW group had a significantly better (p < 0.05) postural stability under static conditions than the NW group. There were no significant differences in postural limit tests and in two-point discrimination between the groups. The DW group had significantly higher values of ankle plantar flexor and knee extensor strengths, while there were no significant differences in ankle dorsiflexors and knee flexors. None of the DW group reported experiencing a fall during the previous 6 months compared with 16% in the NW group who reported at least two falls during the last half year. CONCLUSIONS: Walking on a regular basis in old age may have the potential to modulate stability. It was found that healthy older subjects, who walked on a regular basis since their retirement, have better postural control, especially in their static balance, than those who do not. The laboratory results were accompanied by the important finding that although older subjects who walk on a regular basis walked much more than nonwalkers, they did not suffer from falls.

Accidental Falls↗
PubMed2004

Association of pontine small infarction (lacuna) with disturbance of postural stability.

Neuronal degeneration within the brainstem has been reported in patients with impaired postural stability. However, the functional significance of these abnormalities is unknown at present. In the present study, we evaluated the relationship between the presence of pontine lacunae and postural stability measured by stabilometry. A total of 209 consecutive patients without neurological signs were divided into three groups according to the territory of lacunae on magnetic resonance imaging: (1) non-lacunar group, (2) pontine lacunar group, and (3) non-pontine lacunar group. Stabilometry was performed and statokinesigram measures including each Romberg quotient were compared among the three groups. Using multivariate analysis, postural stability was found to be disturbed in the pontine lacunar group compared with the other groups. The data of stabilometry in this group were compatible with disturbance of the central controlling system for keeping postural stability. Pontine lacuna is associated with patients with postural instability. This result may be related to the deterioration of the central coordination system for posture and locomotion.

Adult↗
PubMed1978

Locomotion and posture in Ateles geoffroyi and Ateles paniscus.

The locomotor and postural behavior of Ateles geoffroyi and Ateles paniscus was studied in Panama and Surinam. Ateles locomotion can be divided into five patterns on the basis of limb usage: quadrupedal walking and running, suspensory locomotion, climbing, bipedalism and leaping. The first three are commonly used in both locomotion during travel and locomotion during feeding, but climbing (especially 'horizontal climbing') is the most important pattern during feeding. Most Ateles locomotion takes place on twigs and branches, with twigs playing a greater role in feeding than in travel. Feeding postures are mainly suspensory and seated, short resting postures are suspensory, seated and standing, and long resting postures are almost entirely seated and reclining. Twigs are the most important supports in feeding postures, but branches are much more important in resting postures. The results of this study indicate that the quadrumanous climbing, forelimb-dominated locomotion during feeding that FLEAGLE considers the primary hominoid adaptation is also characteristic of Ateles.

Animals↗
PubMed2004

Familial and genomic analyses of postural changes in systolic and diastolic blood pressure.

The physiological adaptation to the erect posture involves integrated neural and cardiovascular responses that might be determined by genetic factors. We examined the familial- and individual-specific components of variance for postural changes in systolic and diastolic blood pressure in 767 volunteer nuclear adult families from the Victorian Family Heart Study. In 274 adult sibling pairs, we made a genome-wide scan using 400 markers for quantitative trait loci linked with the postural changes in systolic and diastolic pressures. Overall, systolic pressure did not change on standing, but there was considerable variation in this phenotype (SD=8.1 mm Hg). Familial analyses revealed that 25% of the variance of change in systolic pressure was attributable to genetic factors. In contrast, diastolic pressure increased by 6.3 mm Hg (SD=7.0 mm Hg) on standing and there was no evidence of contributory genetic factors. Multipoint quantitative genome linkage mapping suggested evidence (Z=3.2) of linkage of the postural change in systolic pressure to chromosome 12 but found no genome-wide evidence of linkage for the change in diastolic pressure. These findings suggest that genetic factors determine whether systolic pressure decreases or increases when one stands, possibly as the result of unidentified alleles on chromosome 12. The genetics of postural changes in systolic blood pressure might reflect the general buffering function of the baroreflex; thereby, the predisposition to sudden decreases or increases in systolic pressure might cause postural hypotension or vessel wall disruption, respectively.

Adult↗
PubMed1967

Postural augmentation of plasma renin activity and aldosterone excretion in normal people.

Peripheral plasma renin activity and aldosterone excretion rates have been measured in normal people during recumbency, recumbent exercise, tilting, and continuous ambulation. Upright posture induces a prompt elevation in peripheral plasma renin activity beginning in 15 minutes and peaking between 60 and 120 minutes. Aldosterone excretion is increased during 120 minutes of upright posture and correlates directly with the elevation in renin activity. Upright posture induces increased plasma renin activity regardless of the level of sodium intake in the preparatory diet. Concomitant measurements of endogenous creatinine clearance and the rates of excretion of sodium and potassium suggest that a fall in renal arterial perfusion resulting from upright posture induces increased release of renin and the subsequent secondary stimulation of aldosterone secretion. Our data indicate that the changes in plasma renin activity are due to changes in the amount of the enzyme rather than to changes in other elements of the reninangiotensin systm. This report discusses the physiologic importance of postural augmentation of renin production, emphasizing that for proper interpretation of values of plasma renin activity, posture as well as dietary factors must be considered and controlled.

Aldosterone↗
PubMed1990

Variation of approximal tooth contact tightness with postural change.

In order to investigate the role played by posture in determining posterior dental contact tightness, we measured contact tightness of maxillary and mandibular posterior teeth in ten adult subjects, while each was initially seated upright, after each had assumed a supine posture for two h, and finally after each had returned to an upright posture for two h. The technique used for measurement of contact tightness was based on frictional force concepts and consisted of the recording of the force required to withdraw a 0.038-mm-thick stainless-steel strip that had been slipped into each contact. A decreased mean tightness of all maxillary and mandibular contacts followed the change from an upright to a supine posture. The most significant decrease (-32%) occurred at the mandibular first molar-second premolar contact, and the smallest decrease (-10%) occurred at the mandibular first premolar-canine contact. An increased mean tightness of all maxillary and mandibular contacts followed a return to an upright posture. The most significant increase (20%) occurred at the maxillary first molar-second premolar contact, and the smallest increase (8%) occurred at the maxillary first premolar-canine contact. We conclude that posterior dental contact tightness, generally regarded by dentists as a static feature of occlusion, varies significantly as a function of posture.

Adult↗
PubMed1999

Inter-rater reliability of postural observation after stroke.

OBJECTIVE: To explore the inter-observer reliability of bedside observations of stroke patients' posture using two versions of a pictorial tool. DESIGN: Three projects were conducted. The initial version of the tool was used in project 1. The modified version was used in projects 2 and 3. In each project a pair of observers (comprising the main observer and one of five co-observers with varying degrees of experience in observing posture) used the tool to make simultaneous observations of 19 aspects of the posture of a sample of stroke patients. Each patient was observed in one or more of four positions (seated, supine and lying on the affected and unaffected side). The degree of inter-observer agreement was sought by calculating kappa values and percentage agreement. SETTING: Medical wards, care of the elderly wards and a stroke unit. SUBJECTS: A convenience sample of 57 stroke patients. RESULTS: Four hundred and forty paired sets of observations were made (200 in project 1, 140 in project 2 and 100 in project 3). The main observer was in every pair. The co-observers made between 50 and 135 sets of observations each. When the results from all three projects were amassed, acceptable percentage agreement (i.e. > or =70%) was obtained for 67% (n = 78) and 73% (n = 55) of the results collected on aspects of the posture of the affected upper and lower limbs respectively. In contrast, acceptable percentage agreement for observations relating to the head, neck and trunk was obtained for only 34% (n = 50) of the results collected. Uneven distributions in the data made kappa values difficult to interpret. Inter-observer agreement was not noticeably higher for pairs in which both observers had prior experience of observing posture after stroke than for pairs in which one observer was relatively inexperienced. CONCLUSIONS: The tool has potential as a quick and simple means of collecting information at the bedside about stroke patients' posture. Refinements, additional training in using the tool for observers and further testing are suggested before its wider use is advocated.

Adult↗
PubMed2005

Ankle joint proprioception and postural control in basketball players with bilateral ankle sprains.

BACKGROUND: Deficiencies in ankle proprioception and standing balance in basketball players with multiple ankle sprains have been reported in separate studies. However, the question of how ankle proprioceptive inputs and postural control in stance are related is still unclear. HYPOTHESIS: Ankle repositioning errors and the amount of postural sway in stance are increased in basketball players with multiple ankle sprains. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty healthy male basketball players and 19 male basketball players who had suffered bilateral ankle sprains within the past 2 years were examined. Both groups were similar in age. Passive ankle joint repositioning errors at 5 degrees of plantar flexion were used to test for ankle joint proprioception. The Sensory Organization Test was applied with dynamic posturography to assess postural sway angle under 6 sensory conditions. RESULTS: A significant increase in ankle repositioning errors was demonstrated in basketball players with bilateral ankle sprains (P < .05). The mean errors in the right and left ankles were increased from 1.0 degrees (standard deviation, 0.4 degrees ) and 0.8 degrees (standard deviation, 0.2 degrees ), respectively, in the healthy players to 1.4 degrees (standard deviation, 0.7 degrees ) and 1.1 degrees (standard deviation, 0.5 degrees ) in the injured group. A significant increase in the amount of postural sway in the injured subjects was also found in conditions 1, 2, and 5 of the Sensory Organization Test (P < .05). Furthermore, there were positive associations between averaged errors in repositioning both ankles and postural sway angles in conditions 1, 2, and 3 of the Sensory Organization Test (r = 0.39-0.54, P < .05). CONCLUSIONS: Ankle repositioning errors and postural sway in stance increased in basketball players with multiple ankle sprains. A positive relationship was found between these 2 variables. CLINICAL RELEVANCE: Such findings highlight the need for the rehabilitation of patients with multiple ankle sprains to include proprioceptive and balance training.

Adult↗
PubMed2005

Does head posture have a significant effect on the hyoid bone position and sternocleidomastoid electromyographic activity in young adults?

The aim of this study was to evaluate the associations between head posture (head extension, normal head posture, and head flexion) and anteroposterior head position, hyoid bone position, and the sternocleidomastoid integrated electromyographic (IEMG) activity in a sample of young adults. The study included 50 individuals with natural dentition and bilateral molar support. A lateral craniocervical radiograph was taken for each subject and a cephalometric analysis was performed. Head posture was measured by means of the craniovertebral angle formed by the MacGregor plane and the odontoid plane. According to the value of this angle, the sample was divided into the following three groups: head extension (less than 95 degrees); normal head posture (between 95 degrees and 106 degrees); and head flexion (more than 106 degrees). The following cephalometric measurements were taken to compare the three groups: anteroposterior head position (true vertical plane/pterygoid distance), anteroposterior hyoid bone position (true vertical plane-Ha distance), vertical hyoid bone position (H-H' distance in the hyoid triangle), and CO-C2 distance. In the three groups, IEMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing bipolar surface electrodes on the right and left sternocleidomastoid muscles. In addition, the condition with/without craniomandibular dysfunction (CMD) in each group was also assessed. Head posture showed no significant association with anteroposterior head position, anteroposterior hyoid bone position, vertical hyoid bone position, or sternocleidomastoid IEMG activity. There was no association to head posture with/without the condition of CMD. Clinical relevance of the results is discussed.

Adult↗
PubMed2000

An experimental controlled study on postural sway and therapeutic exercise in subjects with low back pain.

OBJECTIVES: To describe postural sway and its associations to background factors, low back pain and functional capacity. To evaluate the changes in postural sway after three months of therapeutic exercise in the gym or at home. DESIGN: A one-year randomized experimental trial evaluated postural sway in three study groups: intensive training, home exercise and control group. SETTING: Subjects were recruited from seven local occupational health care centres in Central Finland and were examined at Central Finland Hospital by medical doctors. Measurements and therapeutic exercise programmes were carried out in the Research Laboratory of Sport and Health Sciences at Jyväskylä University. SUBJECTS: Initially, 49 male and 41 female subjects (aged 20-55 years) with nonspecific and subacute low back pain were examined. MAIN OUTCOME MEASURES: Postural sway using a force platform, the Oswestry Index, as well as a measure of low back pain intensity were measured at the initial stage of the study, directly after interventions, as well as at three and nine months after the interventions. RESULTS: The background variables were not strongly correlated with postural sway. No changes occurred in the amplitude of sway during the study, but the sway velocity of the home exercise group increased. CONCLUSIONS: Postural sway measurements with a force platform may be suitable for detecting impairments of balance performance among subjects with pronounced functional or activity limitations and severe low back pain problems. In order to enhance balance performance, specific and customized exercise programmes are required.

Adult↗
PubMed2005

Effect of 3,4-diaminopyridine on the postural control in patients with downbeat nystagmus.

Downbeat nystagmus (DBN) is a common, usually persistent ocular motor sign in vestibulocerebellar midline lesions. Postural imbalance in DBN may increase on lateral gaze when downbeat nystagmus increases. 3,4-Diaminopyridine (3,4-DAP) has been shown to suppress the slow-phase velocity component of downbeat nystagmus and its gravity-dependent component with concomitant improvement of oscillopsia. Because the pharmacological effect is thought to be caused by improvement of the vestibulocerebellar Purkinje cell activity, the effect of 3,4-DAP on the postural control of patients with downbeat nystagmus syndrome was examined. Eye movements were recorded with the video-based Eyelink II system. Postural sway and pathway were assessed by posturography in lateral gaze in the light and on eye closure. Two out of four patients showed an improvement of the area of postural sway by 57% of control (baseline) on eye closure. In contrast, downbeat nystagmus in gaze straight ahead and on lateral gaze did not benefit in these two patients, implying a specific influence of 3,4-DAP on the vestibulocerebellar control of posture. It was concluded that 3,4-DAP may particularly influence the postural performance in patients with downbeat nystagmus.

4-Aminopyridine↗
PubMed2003

Postural adjustments in preterm infants at 4 and 6 months post-term during voluntary reaching in supine position.

Gradually it is getting clear that motor development - in particular balance control - in so-called "low-risk" preterm infants often differs from that in full-term infants. However, little is known on the etiology and pathophysiology of these problems. The aim of this study was to evaluate postural behavior during reaching by means of kinetic and kinematic measurements. Preterm infants (n = 32) without cerebral palsy were investigated longitudinally at the corrected ages of 4 and 6 mo. Thirteen age-matched full-term infants served as controls. Cognitive and motor development were assessed by means of the quality of General Movements (GMs) at 4 mo and Bayley scales at 6 and 12 mo. The infants were lying supine on a forceplate reaching for a toy and the kinetics of the total body's Center of Pressure (COP) was measured in cranial-caudal and medial-lateral direction. The analysis focused on COP displacement, Vmax and oscillatory changes of the COP displacement during reaching. The kinematic analysis of reaching focused on movement units, Vmax and a compound kinematic variable reflecting the quality of reaching. The results showed that preterm infants showed a remarkable "still" postural behavior, which differed significantly from the mobile COP behavior of the full-term infants. More "still" postural behavior at 6 mo was associated with a better quality of reaching movements and with normal GMs at 4 mo. We concluded that "still" postural behavior is an adequate postural strategy of preterm infants. But it might be that this postural behavior is an indicator of later dysfunction.

Biomechanical Phenomena↗
PubMed1986

Dopamine inhibits the aldosterone response to upright posture.

Aldosterone secretion in man is stimulated by potassium, ACTH, and angiotensin II and is inhibited by dopamine (DA). In normal sodium-replete supine individuals, aldosterone secretion is under maximum tonic inhibition by DA. Dopaminergic control of aldosterone secretion is modified by dietary sodium depletion. To determine the physiological significance of dopaminergic inhibition of aldosterone secretion, we studied the effect of DA on the aldosterone response to upright posture. Twelve normal men were studied while eating an ad libitum sodium diet, and the effect of DA was determined in the supine and upright positions. Plasma aldosterone (PAC), plasma cortisol (F), plasma aldosterone-stimulating factor (ASF), PRA, and blood pressure were measured while the men were supine and after 4 h of upright posture during an infusion of 5% dextrose vehicle and during a DA infusion of 4.0 micrograms/kg X min. The men also were studied as a time control in the supine position while receiving vehicle or DA. PAC increased from a mean basal value of 20.4 +/- 3.2 ng/dl (+/- SE) by 25.9 +/- 5.1 ng/dl to a peak of 44.4 +/- 2.4 ng/dl in response to upright posture during vehicle infusion. The PAC response to upright posture was reduced to 7.4 +/- 1.8 ng/dl (P less than 0.05) when DA was infused. The increase in PRA with upright posture was 3.7 +/- 1.3 ng/ml X h during the vehicle infusion and 4.1 +/- 1.1 ng/ml X h (P = NS) during the DA infusion. ASF, F, and blood pressure were not altered by upright posture and DA. PAC did not change in the six men infused with DA while supine. Therefore, DA inhibits upright aldosterone responses without affecting PRA, ASF, or F.

Adult↗
PubMed1992

Plasma aldosterone response to upright posture and angiotensin II infusion in aldosterone-producing adenoma.

Nineteen patients with primary aldosteronism due to surgically confirmed aldosterone-producing adenoma (APA) were examined to evaluate the response of aldosterone to upright posture and angiotensin II infusion. Upright posture reportedly decreases the plasma aldosterone concentration (PAC) in APA but raises it in idiopathic hyperaldosteronism. However, our findings showed the opposite result, in that the upright posture did not change or raised PAC in 15 of 19 cases (79%). Angiotensin II was infused i.v. at doses from 0.5-2 ng/min.kg body weight in six patients in whom the upright posture raised PAC, but did not raise PAC in all cases. This result supports the assumption that APA is functionally insensitive to angiotensin II. A concomitant rise of ACTH, pretreatment with calcium channel blockade, and other modulating factors may be involved in this PAC rise. Whatever the reason, such a high frequency of patients with increased PAC in APA raises some question about the clinical value of the upright posture test. We believe, then, there is reason to check any interpretation concerning increased PAC in the case of the upright posture test in distinguishing between APA and idiopathic hyperaldosteronism.

Adenoma↗