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PubMed2005

Reliability of upright posture measurements in primary school children.

BACKGROUND: Correct upright posture is considered to be a measure of good musculoskeletal health. Little is known about the usual variability of children's upright standing posture. The aim of this study was to assess differences between repeated measures of upright posture in a group of primary school children. METHODS: Sagittal plane photographs of usual, relaxed upright standing posture of 38 boys and girls aged 5-12 years were taken twice within an hour. Reflective markers were placed over the canthus, tragus, C7 spinous process, greater trochanter and lateral malleolus. Digitising software was used to calculate the x,y plane coordinates, from which five postural angles were calculated (trunk, neck, gaze, head on neck, lower limb). Height, weight, motor control estimates (as measured by the Brace Tests) and presence of recent pain were recorded for each child, and the association between the first test measure of posture angles and these factors was assessed using linear regression and ANOVA models. Multiple ANOVA models were applied to analyse the effect of repeated testing, and significant predictors on the angles. RESULTS: Four of the five postural angles (trunk, neck, head on neck, lower limb) were significantly influenced by age. As age was strongly associated with height (r2 = 0.84) and moderately associated with weight and motor control (r2 = 0.67, 0.56 respectively), these developmental parameters may well explain the age effect on angles. There was no relationship between age and pain reported on either the testing day, or recently, and there was no gender influence on any angle. There was no significant effect of repeated testing on any angle (ICC>0.93). None of the hypothesized predictors were associated with differences in angles from repeated testing. CONCLUSION: This study outlined the variability of relaxed upright standing posture of children aged 5-12 years, when measured twice in an hour. Age influenced the size of the angles but not the variability. While the subject numbers in this study are small, the findings provide useful information on which further studies in posture and its development in pre-adolescent children can be based.

Aging↗
PubMed1998

Postural motor programming in paraplegic patients during rehabilitation.

One of the basic aims in the rehabilitation of thoracic spinal cord injured (SCI) patients concerns the regaining of sitting posture control. This implies the development of new postural strategies requiring the adjustment of motor programming processes. The aim of this study was to investigate the time course of postural reorganization during active, clinical rehabilitation of thoracic SCI patients with different SCI levels. Thus changes in motor programming in sitting balance control were investigated in two groups of complete low or high thoracic SCI patients. At several stages during the rehabilitation process an experiment was held in which sitting posture was perturbed systematically using submaximal reaching movements over four reaching distances. This bimanual reaching task was presented as a visual precue choice reaction time (RT) task in which reaching distance (i.e. grade of postural perturbation) was precued. Results indicated that in both high and low thoracic SCI patients RTs in movements involving postural perturbation became shorter during the course of the rehabilitation period. However, low thoracic SCI patients were generally slower in the programming of balance perturbing movements than high thoracic SCI patients, a phenomenon that did not change over time. Furthermore, initial differences in RTs as a function of grade of postural perturbation disappeared in both groups in the course of the rehabilitation phase. Precue benefit, equally large for both groups, did not change as a function of rehabilitation time. It is concluded that the observed phenomena signify the gradual development of new central postural control processes in both SCI groups during rehabilitation. Low thoracic SCI patients, having more residual sensorimotor functions, seem to adopt more complex strategies in maintaining and restoring sitting balance that take longer to specify and to programme. High thoracic SCI patients seem to rely on simpler strategies using more passive postural support.

Adolescent↗
PubMed2005

Internal models in sensorimotor integration: perspectives from adaptive control theory.

Internal models and adaptive controls are empirical and mathematical paradigms that have evolved separately to describe learning control processes in brain systems and engineering systems, respectively. This paper presents a comprehensive appraisal of the correlation between these paradigms with a view to forging a unified theoretical framework that may benefit both disciplines. It is suggested that the classic equilibrium-point theory of impedance control of arm movement is analogous to continuous gain-scheduling or high-gain adaptive control within or across movement trials, respectively, and that the recently proposed inverse internal model is akin to adaptive sliding control originally for robotic manipulator applications. Modular internal models' architecture for multiple motor tasks is a form of multi-model adaptive control. Stochastic methods, such as generalized predictive control, reinforcement learning, Bayesian learning and Hebbian feedback covariance learning, are reviewed and their possible relevance to motor control is discussed. Possible applicability of a Luenberger observer and an extended Kalman filter to state estimation problems-such as sensorimotor prediction or the resolution of vestibular sensory ambiguity-is also discussed. The important role played by vestibular system identification in postural control suggests an indirect adaptive control scheme whereby system states or parameters are explicitly estimated prior to the implementation of control. This interdisciplinary framework should facilitate the experimental elucidation of the mechanisms of internal models in sensorimotor systems and the reverse engineering of such neural mechanisms into novel brain-inspired adaptive control paradigms in future.

Adaptation, Physiological↗
PubMed2003

Short-term autonomic control of cardiovascular function: a mini-review with the help of mathematical models.

In this work the main aspects of the short-term regulation of the cardiovascular system are reviewed and critically discussed, laying special emphasis on the role of the autonomic neural mechanisms involved, on their mutual interrelationships and complex integration. All these aspects are summarized with the help of mathematical models developed by the authors in past years. The main characteristics of the uncontrolled system (i.e., the heart and vessels) and of the efferent neural branches (sympathetic and vagal) working on it are first described. Then, the afferent pathways which participate in feedback mechanisms (baroreceptors, chemoreceptors, lung-stretch receptors, direct CNS response), and the feedforward mechanisms anticipating cardiovascular requirements are introduced, and their role discussed with reference to various cardiovascular perturbations (hemorrhage or posture changes, hypoxia, asphyxia, dynamic exercise). Analysis of physiological data via mathematical equations, and results of computer simulations, emphasize the great complexity, richness and variability of the autonomic cardiovascular control, including redundant mechanisms and antagonistic requirements. The use of mathematical models is essential to capture this richness, and to summarize apparent contradictory data into a coherent and comprehensive theoretical setting.

Animals↗
PubMed1996

A body model server for human motion capture and representation.

This paper presents a body model server (BMS) that provides real-time access to the position and posture of a person's torso, arms, hands, head, and eyes. It can be accessed by clients over a network. The BMS is designed to function as a device-independent data-layer between the sensing devices and client applications that require real-time human motion data, such as animation control. It can provide clients with accurate information at up to 40 Hz. For data collection, the model uses four magnetic position/orientation sensors, two data-gloves, and an eye-tracker. The BMS combines the data-streams from the sensors and transforms them into snapshots of the user's upper-body pose. A geometric model made up of joints and segments structures the input. Posture of the body is represented by joint angles. Two unique characteristics of our approach are the use of the implicit, geometric constraints of the sensed body to simplify the computation of the unmeasured joint angles, and the use of time-stamped data that allow synchronization with other data streams, e.g., speech input. This paper describes the architecture of the BMS, including the management of multiple input devices, the representation and computation of the position and joint angle data, and the client-server interface.

Computer Simulation↗
PubMed2006

Quantification of intrinsic and reflexive properties during multijoint arm posture.

This study estimates intrinsic and reflexive properties of single- and two-joint muscles acting around the human shoulder, elbow and wrist joint during posture maintenance. External force disturbances were applied to the hand while subjects (n = 5) were instructed to minimize their hand displacement amplitude in a horizontal plane. To examine how the nervous system modifies intrinsic and reflexive muscle properties, we varied external damping, disturbance power and arm configuration. A new identification method is introduced to quantify a large set of model parameters describing intrinsic, activation and reflexive properties, the latter representing afferent feedback gains from muscle spindles and Golgi tendon organs. Consistent estimates were found for the gains of the different types of reflex pathways. The results showed that intrinsic visco-elasticity of shoulder muscles was minimal, whereas reflexive feedback was largest compared to the elbow and wrist joint. Intrinsic and reflexive properties of the two-joint shoulder-elbow muscles were larger than the two-joint elbow-wrist muscles. Contrasting to previous single-joint studies, the reflex gains did not vary with the experimental conditions. It is concluded that during redundant multijoint posture maintenance, the mechanical properties are efficiently controlled on the joint level and not on the endpoint level.

Adult↗
PubMed1978

Behavioural evidence for GABAergic activity of the benzodiazepine flurazepam.

Following reports that unilateral intranigral injections of putative GABAergic drugs induce contralateral rotational behaviour in rats, the effects of similar injections of the benzodiazepine flurazepam have been studied. Flurazepam mimicked the effects of the GABA agonist muscimol and the GABA analogue baclofen by inducing a dose-related contralateral rotation. This response was anatomically associated with the GABA-rich zona reticulata of the substantia nigra and was attenuated by the GABA antagonist picrotoxin but not by the dopamine antagonist haloperidol or by destruction of the ipsilateral nigrostriatal dopamine pathway with 6-hydroxydopamine. These results suggest that in this behavioural model flurazepam may show GABAergic activity by indirectly enhancing GABA transmission at synapses with receptors located on nigral non-dopaminergic neurons controlling postural asymmetry.

Animals↗
PubMed2006

The influence of sensory information on two-component coordination during quiet stance.

When standing quietly, human upright stance is typically approximated as a single segment inverted pendulum. In contrast, investigations, which perturb upright stance with support, surface translations or visual driving stimuli have shown that the body behaves like a two-segment pendulum, displaying both in-phase and anti-phase patterns between the upper and lower body. We have recently shown that these patterns co-exist during quiet stance; in-phase and anti-phase for frequencies below and above 1 Hz, respectively. Here we investigated whether the characteristics of these basic patterns were influenced by the addition or removal of sensory information. Ten healthy young subjects stood upright on a rigid platform with different combinations of sensory information: eyes were open or closed with or without light touch contact (<1N) of the right index fingertip with a 5 cm diameter rigid force plate. The in-phase and anti-phase pattern co-exist in both the anterior-posterior (AP) and medial-lateral (ML) directions of sway. The real part of trunk-leg complex coherence decreased with the addition of vision and light touch, corresponding to a transition from the in-phase to anti-phase pattern at a lower frequency. In the AP direction, the decrease was only observed at frequencies below 1 Hz where the in-phase pattern predominates. Additional sensory information had no observable effect at sway frequencies above 1 Hz, where the anti-phase pattern predominates. Both patterns are clearly the result of a double-linked inverted pendulum dynamics, but the coherence of the in-phase pattern is more susceptible to modulation by sensory information than the anti-phase pattern.

Adult↗
PubMed1999

A biomechanical study of equilibrium in sport rock climbing.

One of the main objectives of the experiment reported in this article was to analyze the arrangement of the forces applied to the holds accompanying a voluntary right foot release in the hanging rock climber. The three dimensional reaction forces applied to the holds were measured using four holds equipped with strain gauges. The force arrangement after the release consisted of a tripedal stance on the three remaining holds for the vertical forces, and of a bipedal stance on two laterally opposite holds (left foot and left holds) for the horizontal forces. The general significance of the results was analyzed with respect to the mechanism of static equilibrium. However, before conclusions can be drawn, other climbing movements and positions must be analyzed.

Adult↗
PubMed2000

The relationship of maternal position to the results of brief nonstress tests: a randomized clinical trial.

OBJECTIVE: This study was undertaken to determine whether maternal posture (left lateral recumbent vs semi-Fowler position) had any effect on nonstress test results when the test was performed for a shortened period (10 minutes). STUDY DESIGN: In this randomized clinical trial of 108 patients with singleton pregnancies at 32 to 42 weeks' gestation, patients were randomly assigned to a "sitting first" (semi-Fowler position) or a "supine first" (left lateral recumbent position) group at the initial visit. The order of position was alternated at subsequent visits. Ten minutes of fetal heart rate monitoring was performed in each position at each visit. Computer analysis of the nonstress test was used to interpret each 10-minute segment for reactivity. Statistical analyses were performed on the paired nonstress test unit (sitting and supine). RESULTS: There were no adverse clinical outcomes among the participants. Logistic regression analysis showed that both the sequence of the nonstress test and the position were significant and independent factors related to nonstress test reactivity. Tests performed during the second 10 minutes and tests performed with the patient in the semi-Fowler position were more likely to have reactive results. CONCLUSION: The semi-Fowler position is a superior position for conducting a nonstress test in a short period. Use of this position could decrease the need for prolonged monitoring, thus leading to a more time-effective evaluation of patients at risk.

Female↗
PubMed1998

The effect of changes in hearing status on speech sound level and speech breathing: a study conducted with cochlear implant users and NF-2 patients.

According to a dual-process theory of the role of hearing in speech production, hearing helps maintain an internal model used by the speech control mechanism to achieve phonemic goals. It also monitors the acoustic environment and guides relatively rapid adjustments in postural parameters, such as those underlying average speech sound level and rate, in order to achieve suprasegmental goals that are a compromise between intelligibility and economy of effort. In order to obtain evidence bearing on this theory, acoustic and aerodynamic measures were collected from seven adventitiously deaf speakers who received cochlear implants, three speakers who had severe reduction in hearing following surgery for Neurofibromatosis-2, and one hard of hearing speaker. These speakers made recordings of the Rainbow Passage and an English vowel inventory before and after intervention. All but one of the postlingually deaf speakers who received prosthetic hearing reduced speech sound level, SPL. Three of these significantly increased a measure of inferred glottal aperture, H1-H2, and their session means for these two parameters were inversely correlated longitudinally. All but one of the speakers terminated respiratory limbs closer to functional residual capacity (FRC) once prosthetic hearing was supplied. Finally, the implant users' average values of air expenditure moved toward normative values with prosthetic hearing. These results are attributed to the mediation of changes in respiratory and glottal posture aimed at reducing speech sound level and economizing effort.

Adult↗
PubMedDate not supplied

Aging and attenuated processing robustness. Evidence from cognitive and sensorimotor functioning.

BACKGROUND: Within-person, across-time variations in processes and performance are intrinsic to all aspects of human functioning. OBJECTIVE: This article starts with a brief taxonomy of intraindividual dynamics. There are adaptive as well as non-adaptive types of intraindividual variations that unfold with different degrees of reversibility on different time scales and involve either single, or systems of, functions. METHODS: Empirical findings regarding aging and a specific type of intraindividual variation, namely attenuated processing robustness, are then presented with respect to cognitive and sensorimotor functioning. RESULTS: In both domains of functioning, old adults exhibit less robust functioning with a greater amount of week-to-week, day-to-day, or trial-by-trial fluctuations in their cognitive, walking, and postural control performances. CONCLUSION: Currently, the causes for the attenuation of processing robustness in cognitive and sensorimotor functioning are not well understood. Neurocomputational models are useful tools for exploring the tripartite relationships between the aging of neural information-processing fidelity, and cognitive, and sensorimotor processes.

Aging↗
PubMed2006

Sagittal jaw position in relation to body posture in adult humans--a rasterstereographic study.

BACKGROUND: The correlations between the sagittal jaw position and the cranio-cervical inclination are described in literature. Only few studies focus on the sagittal jaw position and the body posture using valid and objective orthopaedic examination methods. The aim of this study was to test the hypothesis that patients with malocclusions reveal significant differences in body posture compared to those without (upper thoracic inclination, kyphotic angle, lordotic angle and lower lumbar inclination). METHODS: Eighty-four healthy adult patients (with a mean age = 25.6 years and ranging from 16.1 to 55.8 years) were examined with informed consent. The orthodontic examination horizontal overjet (distance between upper and lower incisors) was determined by using an orthodontic digital sliding calliper. The subjects were subdivided in respect of the overjet with the following results: 18 revealed a normal overjet (Class I), 38 had an increased overjet (Class II) and 28 had an reversed overjet (Class III). Rasterstereography was used to carry out a three-dimensional back shape analysis. This method is based on photogrammetry. A three-dimensional shape was produced by analysing the distortion of parallel horizontal white light lines projected on the patient's back, followed by mathematical modelling. On the basis of the sagittal profile the upper thoracic inclination, the thoracic angle, the lordotic angle and the pelvic inclination were determined with a reported accuracy of 2.8 degrees and the correlations to the sagittal jaw position were calculated by means of ANOVA, Scheffé and Kruskal-Wallis procedures. RESULTS: Between the different overjet groups, no statistically significant differences or correlations regarding the analysed back shape parameters could be obtained. However, comparing males and females there were statistically significant differences in view of the parameters 'lordotic angle' and 'pelvic inclination'. CONCLUSION: No correlations between overjet and variables of the thoracic, lordotic or the pelvic inclination could be observed.

Adolescent↗
PubMedDate not supplied

[Difference between arterial and end-tidal carbon dioxide tension during surgery of lumbar herniated disk in general anesthesia].

OBJECTIVE: To determine the correlation of PaCO2 and ETCO2 during operations for lumbar disk herniation in prone position: the influence of position and deliberate hypotension. DESIGN: Prospective, to compare PaCO2, ETCO2, pH, SBE, Pa max, in a group of 10 patients undergoing elective intervention for lumbar disk herniation in prone position and in a control group of 10 patients undergoing interventions for elective non traumatologic orthopaedic surgery of the lower limbs in supine position. SETTING: Orthopaedic department of a non teaching hospital. MEASUREMENTS AND MAIN RESULTS: The results for the patients of the supine group were: mean PaCO2 35.26 mmHg (SD 3.045), mean P(a-ET)CO2 3.46 mmHg (SD 1.898), mean pH 7.433 (SD 0.044), mean SBE - 1.16 (SD 1.718), mean Pa max 122.5 mmHg (SD 17.989). In the prone group: mean PaCO2 30.3 mmHg (SD 5.819), mean P(a-ET)CO2 1.4 mmHg (SD 4.445), mean pH 7.430 (SD 0.052), mean SBE-3.93 (SD 3.255), mean Pa max 100.3 (SD 10.945). The difference was significant (p < 0.05) for pH, PaCO2, SBE; in the prone group the variability of P(a-ET)CO2 was greater and the values related with SBE. CONCLUSIONS: ETCO2 is a useful monitoring for PaCO2 in the situation evaluated but the accuracy of the correlation with PaCO2 is lesser than during standard surgical techniques, the metabolic acidosis observed is probably related to the effects of the peculiar position and the anaesthetic technique.

Adult↗
PubMed1995

A case-control study of routine and death scene sleep position and sudden infant death syndrome in Southern California.

OBJECTIVE: To investigate whether infants who died of sudden infant death syndrome (SIDS) were routinely placed in different sleep positions compared with healthy infants in a multiethnic diverse population in the United States. DESIGN: A population-based case-control study. SETTING: Five counties in Southern California including Los Angeles, Orange, San Bernardino, Riverside, and San Diego. PARTICIPANTS: Parents of 200 white, African-American, Hispanic, and Asian infants who died of SIDS between January 1989 and December 1992 and parents of 200 healthy, living infants matched on the basis of birth hospital, birth date, race, and gender. Information was obtained from detailed telephone interviews with the parents and validated with obstetric and pediatric records. MAIN OUTCOME MEASURES: Routine sleep position, type of bedding, and objects in bed were determined for both case and control infants, while the last-placed and found sleep and face positions at death were reported for SIDS infants. RESULTS: Approximately 66% of SIDS infants and 64% of comparison infants routinely slept on their abdomens (P = .91). At the time of death, 80% of cases were found sleeping on their abdomens. There was no difference in routine sleep position for SIDS infants and comparison infants (odds ratio = 0.76; 95% confidence interval, 0.42 to 1.38), while simultaneously adjusting for birth weight (in grams), medical conditions at birth, breast-feeding, passive smoking, maternal recreational drug use, prenatal care, and infant vomiting. Hispanic parents routinely placed their infants on their abdomens less frequently than white parents (P < .01). However, the prone sleep position (face down) was the most commonly found sleep position at death in both Hispanic and non-Hispanic infants. CONCLUSIONS: Routine prone sleep position was not associated with an increased risk of SIDS in this study population. The results need to be confirmed with other parents of SIDS infants interviewed before the height of publicity regarding prone sleep position in the United States.

California↗
PubMedDate not supplied

Motor coordination in weightless conditions revealed by long-term microgravity adaptation.

The functional approach to studying human motor systems attempts to give a better understanding of the processes behind planning movements and their coordinated performance by relying on weightlessness as a particularly enlightening experimental condition. Indeed, quantitative monitoring of sensorimotor adaptation of subjects exposed to weightlessness outlines the functional role of gravity in motor and postural organization. The recent accessibility of the MIR Space Station has allowed for the first time experimental quantitative kinematic analysis of long-term sensorimotor and postural adaptation to the weightless environment though opto-electronic techniques. In the frame of the EUROMIR'95 Mission, two protocols of voluntary posture perturbation (erect posture, EP; forward trunk bending, FTB) were carried out during four months of microgravity exposure. Results show that postural strategies for quasistatic body orientation in weightlessness are based on the alignment of geometrical body axes (head and trunk) along external references. A proper whole body positioning appears to be recovered only after months of microgravity exposure. By contrast, typically, terrestrial strategies of co-ordination between movement and posture are promptly restored and used when performing motor activities in the weightless environment. This result is explained under the assumption that there may be different sensorimotor integration processes for static and dynamic postural function and that the organisation of coordinated movement might rely stably on egocentric references and kinematics synergies for motor control.

Adaptation, Physiological↗
PubMedDate not supplied

[Motor cortex functions in the reorganization of postural coordinations].

A well-known function of the motor cortex (MCx) is control of the limb distal musculature, in particular, isolated finger movements during precise and fine hand movements. However, MCx has another function connected with the motor learning process, namely, a suppression of synergies and coordinations interfering with a movement being elaborated. This was shown for various limb movements. However, majority of movements is accompanied by postural adjustment as well. Two experimental models of rearrangement of an innate pattern of the postural adjustment were developed, and MCx was shown during such kind of learning to suppress the activity of structures providing the innate postural patterns. In contrast to the control of limb movements, the MCx influences were found to be bilateral for the postural pattern reorganization. It was revealed recently, however, that a possibility of recovery for the sequential MCx lesions depends on the sequence of the lesions, so, perhaps the role of MCx of different hemispheres in the compensation is different.

Animals↗