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PubMed1997

[Age-dependent changes in dynamic body balance as evaluated by the body tracking test (BTT)].

Stability of posture and gait is improved by growth and decays with aging. Maturational changes and deterioration of static posture with aging have been determined by using gravic body sway tests. In this study, we constructed a new system, the Body Tracking Test (BTT), to evaluate dynamic body balance function as opposed to static balance. Preliminary results of the study were previously reported elsewhere. Healthy volunteers of various ages (total, 516 persons) were subjects of the study. The principle of the BTT is for the subject to attempt to track an optical moving target displayed on the computer screen by shifting his or her body center of gravity that was also displayed on it. The target moved for a span of 15 cm horizontally on the 14-inch screen. The movement was lateral and antero-posterior (horizontal and vertical) in direction at a constant velocity of 0.125 Hz. The recording was for 60 seconds. In BTT the gain for target against tracking was fixed to 2.0 (target: tracking = 1: 2). The target was 100 cm anterior to the platform where the subject was to stand erect with the feet close together. The criteria for evaluation of the tracking function were determined by our preliminary study, the principle of which was to judge the rate of accordance of the tract of the moving target with that of body tracking. The score was divided into five ranks from A to E. We called it "The 5 grade evaluations of tracking ability". Age-dependent changes in the score were obtained and the statistical significance of the value was determined by chi 2 analysis. With regard to both the lateral and antero-posterior tracking abilities, there was an apparent improvement by maturation. The high school students reached the adult level in lateral tracking but not in antero-posterior tracking ability. Also, the tracking ability started to deteriorate after age 40. It is apparent from this study that the balancing or dynamic postural control differs between youth and the elderly, i.e.; lateral control seems to improve faster in youths and older persons tend to balance better in the antero-posterior directions. The BTT requires visual as well as proprioceptive information for its function. Moreover, dynamic maintenance and shifting of muscular tone and strength are prerequisite. In addition, for BTT, reflective postural control is strongly aided by training in terms of efficiency and skills that require higher cerebral functions. The BTT described here thus appears to represent a cumulative effect of the sensory, visual, motor and higher cerebral functions.

Adolescent↗

PubMed1995

Dose-related effects of alcohol on dynamic posturography and oculomotor measures.

Four healthy male volunteers < 30 years of age participated in a blinded study of placebo versus low (0.45 g/kg lean body weight = LBW), medium (0.80 g/kg LBW) and high (1.05 g/kg LBW) dose ethanol ingestion to investigate its effect upon gaze and posture control. Serial electronystagmography and computerized platform posturography were performed at different points along each subject's blood alcohol concentration (BAC) curve as measured by breath analysis. Smooth pursuit and positional testing revealed subtle abnormalities at sub-intoxicating BACs. In addition, instability on posturography was evident on the Sensory Organization Test with no statistically significant influence observed on muscle latency testing as determined by sway analysis. We conclude that even low ethanol BAC levels produce widespread gaze and posture control effects which can be easily documented.

Adult↗

PubMed1996

Postural stability and skilled performance--a study on top-level and naive rifle shooters.

Posture control during aiming over a period of 7.5 s preceding the shot was studied among national top-level rifle shooters as well as among national level shooters and amateurs familiar with rifle shooting. Movement of the center of forces (COF) was analyzed in terms of the speed and amplitude of the movement. These calculations were carried out in 1.5 s windows, the first window beginning 7.5 s and ending at 6.0 s prior the shot. The last window ended at the trigger pull. Posture control data differentiated the studied groups according to their level in competitive shooting. The male top-level shooters could stabilize their posture significantly better than female top-level or male national level shooters, who were, in turn, much more stable than naive shooters. The experienced shooters were able to stabilize their posture even better during the last seconds preceding the shot, whereas in naive shooters there were no significant differences when the successive windows were compared with each other. When a comparison was made between the best and worst 20 shots of each subject, a significant difference in balance parameters was only observed among the naive shooters, who showed more pronounced movement of the COF in the less successful trials. Among the highly trained top-level shooters a miss in whole-body posture stabilization apparently seldom is a reason for a poor result.

Adult↗

PubMedDate not supplied

[Determination of postural behaviour patterns in the Spanish healthy population].

INTRODUCTION: Postural control in a standing position is externally reflected by the displacement of the centre of pressure (COP). It is necessary to determine COP movement normal patterns in order to obtain an accurate balance assessment. MATERIALS AND METHODOLOGY: A non pathological subject group was studied using NED/IBV s. v. e. evaluation equipment. Static trials based on Romberg's test were undertaken in addition to the analysis trials of voluntary postural control. RESULTS: Normal patterns have been obtained for the COP displacement and for the maximum forces produced in the anteroposterior and midlateral axes. CONCLUSIONS: COP movement comparative analysis, related to postural behaviour patterns of non-pathological persons, represents an accurate method to assess postural balance in a standing position. This information enables the design of individual and customised rehabilitation strategies in order to reduce the risk of falling.

Adult↗

PubMed1980

Prevention of falls in the elderly.

To prevent falls effectively, one must first understand the underlying reasons. Although environmental factors are sometimes to blame, the fundamental cause is a decline in postural control which is partly age-related and partly due to pathologic changes in the central nervous system. Dizziness is a common complaint among those who fall, and it is often caused by a central or peripheral vestibular disorder. Many patients who complain of dizziness do not have true vertigo but are expressing a fear of falling. Balance exercises can improve postural control and confidence in these patients. Falls are not inevitable in old age and may be prevented by maintenance of health, mobility and confidence, the avoidance of certain drugs, identification of specific problems such as cardiac arrhythmias or postural hypotension, and attention to environmental hazards.

Accident Prevention↗

PubMed1999

NACOB presentation CSB New Investigator Award. Balance recovery from medio-lateral perturbations of the upper body during standing. North American Congress on Biomechanics.

Postural control strategies have in the past been predominantly characterized by kinematics, surface forces, and EMG responses (e.g. Horak and Nashner, 1986, Journal of Neurophysiology 55(6), 1369-1381). The goal of this study was to provide unique and novel insights into the underlying motor mechanisms used in postural control by determining the joint moments during balance recovery from medio-lateral (M/L) perturbations. Ten adult males received medio-lateral (M/L) pushes to the trunk or pelvis. The inverted pendulum model of balance control (Winter et al., 1998, Journal of Neurophysiology 80, 1211-1221) was validated even though the body did not behave as a single pendulum, indicating that the centre of pressure (COP) is the variable used to control the centre of mass (COM). The perturbation magnitude was random, and the central nervous system (CNS) responded with an estimate of the largest anticipated perturbation. The observed joint moments served to move the COP in the appropriate direction and to control the lateral collapse of the trunk. The individual joints involved in controlling the COP contributed differing amounts to the total recovery response: the hip and spinal moments provided the majority of the recovery (approximately 85%), while the ankles contributed a small, but significant amount (15%). The differing contributions are based on the anatomical constraints and the functional requirements of the balance task. The onset of the joint moment was synchronous with the joint angle change, and occurred too early (56-116 ms) to be result of active muscle contraction. Therefore, the first line of defense was provided by muscle stiffness, not reflex-activated muscle activity.

Adult↗

PubMed2005

Cross-correlation between EMG and center of gravity during quiet stance: theory and simulations.

Several signal processing tools have been employed in the experimental study of the postural control system in humans. Among them, the cross-correlation function has been used to analyze the time relationship between signals such as the electromyogram and the horizontal projection of the center of gravity. The common finding is that the electromyogram precedes the biomechanical signal, a result that has been interpreted in different ways, for example, the existence of feedforward control or the preponderance of a velocity feedback. It is shown here, analytically and by simulation, that the cross-correlation function is dependent in a complicated way on system parameters and on noise spectra. Results similar to those found experimentally, e.g., electromyogram preceding the biomechanical signal may be obtained in a postural control model without any feedforward control and without any velocity feedback. Therefore, correct interpretations of experimentally obtained cross-correlation functions may require additional information about the system. The results extend to other biomedical applications where two signals from a closed loop system are cross-correlated.

Computer Simulation↗

PubMed2003

The effect of clinorotation on vestibular compensation in upside-down swimming catfish.

Upside-down swimming catfish Synodontis nigriventris can keep upside-down swimming posture stably under pseudo-microgravity generated by clinostat. When the vestibular organ is unilaterally ablated, the operated S. nigriventris shows disturbed swimming postures under the clinorotation condition. However, about 1 month after the operation, unilateral vestibular organ-ablated S. nigriventris shows stable upside-down swimming posture under the condition (vestibular compensation). In contrast, a closely related upside-up swimming catfish Synodontis multipunctatus belonging to same Synodontis family can not keep stable swimming postures under the clinorotation conditions. In this study, we examined the effect of continuous clinorotation on vestibular compensation in intact and unilateral vestibular organ-ablated Synodontis nigriventris and Synodontis multipunctatus. After the exposure to continuous clinorotation, the postures of the catfish were observed under microgravity provided by parabolic flights of an aircraft. Unilateral vestibular organ-ablated S. nigriventris which had been exposed to continuous clinorotation showed stable swimming postures and did not show dorsal light reaction (DLR) under microgravity. This postural control pattern of the operated catfish was similar to that of intact catfish. Intact and unilateral vestibular organ-ablated S. multipunctatus showed DLR during microgravity. Our results confirmed that S. nigriventris has a novel balance sensation which is not affected by microgravity. DLR seems not to play an important role in postural control. It remains unclear that the continuous clinorotation effects on vestibular compensation because we could not keep used unilateral vestibular organ-ablated fish alive under continuous clinorotation for uninterrupted 25 days. This study suggests that space flight experiments are required to explore whether gravity information is essential for vestibular compensation.

Animals↗

PubMed2003

Voluntary control of postural equilibrium patterns.

The ability to voluntarily transit from one whole-body movement to another is based on the multisensory integration of visual, vestibular, and somatosensory information. The role of functional sensory ranges and mechanical constraints on the ability to voluntarily transit between whole-body movements was studied by requiring subjects to switch from a head-fixed-to-surface to head-fixed-in-space postural pattern (and vice versa). The head-fixed-to-surface pattern required an erect stance characterized by an in-phase relationship between center of pressure (CoP) and platform motion. The head-fixed-in-space pattern required subjects to fix trunk-head position in-space while producing an anti-phase relationship between CoP and platform motion. The voluntary transition was performed with and without vision while standing on a surface oscillating in the anterior-posterior (A/P) direction. The support surface oscillated at five frequencies (0.2-1Hz) with amplitude fixed at 15cm. The voluntary transition was initiated with an auditory cue. The appropriate CoP-platform phase relationship for the two postural patterns was produced for all frequencies with and without vision. Upper-trunk kinematics revealed that subjects often failed to produce the head-fixed-to-surface pattern for frequencies >/=0.6Hz, while producing the head-fixed-in-space pattern at all frequencies with vision. Without vision, neither pattern was produced consistently based on upper-trunk kinematics. These findings demonstrate separate control processes for upper- and lower-body motion and that functional sensory ranges and mechanical constraints can facilitate or inhibit voluntary production of whole-body movements based on these control processes. The results are discussed in reference to neurological substrates that may be involved in the planning and execution of motor set-switching. The experimental protocol we employ may also have application as a diagnostic tool for the evaluation of postural deficits.

Adaptation, Physiological↗

PubMed2003

Proprioceptive and behavior impairments in individuals with anterior cruciate ligament reconstructed knees.

OBJECTIVE: To assess sensory deficits and their effects on proprioceptive and motor function in patients who had undergone unilateral anterior cruciate ligament (ACL) reconstruction. DESIGN: Four evaluations were conducted: (1) joint position perception of the knee for predetermined angles (0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees ); (2) threshold for detection of passive knee motion at 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60 degrees moving into flexion and at 15 degrees, 30 degrees, 45 degrees, and 60 degrees moving into extension; (3) latency onset of hamstring muscles; and (4) postural control during upright double- and single-leg stance. SETTING: Movement laboratory in Brazil. PARTICIPANTS: Ten participants who had surgical reconstruction of the ACL (reconstructed group) and 10 participants without knee injury (control group). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Absolute error, angular displacement, hamstring muscles latency, and mean sway amplitude. RESULTS: Individuals with a reconstructed knee showed decreased joint position perception, a higher threshold for detection of passive knee motion, longer latency of hamstring muscles, and decreased performance in postural control. CONCLUSIONS: After lesion and ACL reconstruction, sensory and motor behavior changes were still observed. This may be because of the lack of proprioceptive information resulting from the ACL lesion and/or substitution of ACL by the graft.

Adult↗

PubMed2005

Balance control: sex and age differences in 9- to 16-year-olds.

This study investigated sex and age differences in standing balance. Movement of the centre of pressure (COP) was calculated from ground reaction force data collected from a force platform during bipedal stance with eyes open and eyes closed. Three groups of 60 children, with 30 girls and 30 boys in each, were assessed. Mean ages of each group were as follows: 9 years 11 months (standard deviation [SD] 3mo); 12 years 11 months (SD 2mo); and 15 years 11 months (SD 3mo) respectively. Summary sway parameters and frequency domain variables were calculated in the anteroposterior and mediolateral directions. Boys exhibited greater COP movement than girls at 9 to 10 years of age. Age-related 'improvements' in sway occurred in boys, thus some aspects of postural control are still developing after 9 to 10 years of age. As very little age-related difference was seen in girls, boys may lag behind somewhat in terms of developing postural control. Thus there is a need to study the sexes separately when investigating balance in children.

Adolescent↗

PubMed1996

Postural balance and its sensory-motor correlates in 75-year-old men and women: a cross-national comparative study.

BACKGROUND: There are no earlier cross-national comparative studies analyzing the functions of the posture control mechanisms and its sensory-motor correlates in elderly subjects. We investigated whether there are differences in balance between elderly subjects living in different geographical areas, and analyzed the sensory-motor associates of balance in men and women separately. METHOD: Using a force platform method, the functioning of the posture control system under three standardized conditions (normal standing, eyes open; normal standing, eyes closed; and tandem standing, eyes open) was studied among samples of 75-year-old residents in three Nordic localities, namely Glostrup in Denmark, Göteborg in Sweden, and Jyväskylä in Finland. The associations of the variables describing performance in each test with other sensory and motor functions were studied using correlation analyses and multivariate regression models. RESULTS: Differences between the populations were observed in both tests with visual control, favoring the participants from Glostrup and Jyväskylä compared with those from Göteborg. However, only minor differences between the subjects from different localities were observed in the test performed with the eyes closed. In all localities there was a primary sex difference in favor of the women which, however, mainly disappeared when body height was taken into the analyses as a covariate. A good performance in the balance tests (body height-adjusted values) was associated with good visual acuity, low vibrotactile thresholds, and high psychomotor speed. Also, isometric muscle strength, especially hand grip and body extension, was positively associated with good performance in the balance tests. Among the women, a poorer balance was observed in women with a smaller body mass. The results of the multivariate analyses showed that among the men, the most important predictors of good performance in the balance tests were low vibrotactile threshold on the foot, high isometric hand grip strength, and low body stature. Among the women, the most important predictors were low body stature, high body mass, high isometric body extension strength, and high psychomotor speed. However, only a small proportion of the variance in balance (about 13% in the men and 11% in the women) could be explained by the help of these factors. CONCLUSIONS: As the same procedure was applied to the analysis of postural balance, some differences between the populations living in different localities could be detected in some of the tests. The better performance of the women in the balance tests may partly be explained by anthropometric factors, especially differences in body height. There may also be differences in sensory-motor associates of balance in elderly men and women. On the basis of the associations observed, it is difficult to explain the differences in balance between the sexes or subjects living in different localities. Within the sexes, only a small proportion (10-13%) of the variation in balance during normal standing with eyes open could be explained by the factors included in the study.

Aged↗

PubMed2000

[Exercices program and rehabilitation of motor disorders in Parkinson's disease].

As long as motor disorders are controlled by DOPAtherapy, exercise programs and rehabilitation would not appear to be essential for patients suffering from Parkinson's disease. Such measures do become necessary however when secondary occurrence of motor decline develops. Physical medicine and rehabilitation have not been really involved in Parkinson's disease and few articles have assessed the value of these programs. In fact, controlled randomized studies have faced two kinds of methodological difficulties, those due to rehabilitation practices, and those due to Parkinson's disease specificity, especially similarities between groups for Hoehn and Yahr stage at study onset and unchanged drug treatment during the period of the clinical trial. Assessment has had to rely on scales taking into account the main Parkinson impairments (e.g. walking ability, postural control, skill), their intensity and also their fluctuation such as on-off effects. The Unified Parkinson's Disease Rating Scale (UPDRS) looks well-adapted but has been only recently for such studies. Many exercise programs, aiming at improving coordination, sway balance, transfer and gait have been proposed in the literature; rhythmic visual or auditory cueing seem quite effective. Only four controlled studies with satisfactory methodology are available. They could lead to the conclusion that physiotherapy would be effective more by reducing daily life disability than by improving Parkinson symptoms such as bradykinesia or tremor. To be effectively performed at home, these exercises would have to be taught early in the course of the disease and during an on phase, physiotherapists giving special attention to postural control and prevention of falls. In another controlled randomized study occupational therapists successfully trained patients in everyday activities. For the most severely impaired patients, rehabilitation and home adaptations are the only means to achieve an less dependent status. Multidisciplinary outpatient departments providing physical medicine and rehabilitation facilities in addition to neurological care would appear to be the best solution for helping Parkinson's disease patients cope with their impairments and disabilities.

Exercise Therapy↗

PubMed1995

Biomechanical assessment of quiet standing and changes associated with aging.

The kinematics of standing balance were analyzed in 24 normal subjects, aged 21 to 78 years, to examine differences attributable to age, visual input, and sex. Movements of individual body segments, displacement of the center of gravity (COG), and position of the center of pressure (COP) were measured, and total path length and variability about the mean position were derived from the resulting values. Aging was associated with an increase in variability of the COG, head, and hip, but not in path length. The changes, which may be clinically interpreted as excess postural sway, do not show stability deficits as a consequence of aging. On the contrary, older subjects seem to adopt a postural control strategy that achieves comparable stability during quiet standing. Eye closure increased the anterior-posterior COP path length without corresponding changes in the COG, indicating an increase in small accelerations without associated instability. There was more medial-lateral movement in women than in men. Quantitative electromyographic measures showed that, in general, quiet standing requires very little muscular activity. We conclude that the task of quiet standing produces no evidence of postural instability concurrent with aging. The altered postural control strategy may be less effective when balance is suddenly or severely compromised.

Adult↗

PubMed1989

Activity states and motor activity in an infant capuchin monkey (Cebus apella) from birth through eleven weeks.

Behavioral states and motor activity of an infant capuchin monkey reared by its mother in a social group were studied for 11 weeks after birth. Manipulative activity was infrequent through the first four weeks after birth; what little occurred was mediated by other animals interacting with the infant. The rate of manipulation increased the most between weeks 8 and 9. At the same time, the most frequent targets of manipulation shifted from the infant's own body and the bodies of others to surfaces and inanimate objects in the cage. Large increases in the proportion of time in an Alert/active state and improvement in postural control also occurred at the end of the second month. The data suggest that major organizational changes in motor coordination and the regulation of behavioral state occurred jointly over a short period of time at about 8 weeks of age. In comparison to other species of monkeys, the capuchin infant displayed later development of manipulation, postural control, and independent locomotion, and greater dependence on social contacts for early interaction with its environment. These characteristics are in accord with the greater neurological immaturity of the capuchin infant at birth compared to other monkeys.

Aging↗

PubMedDate not supplied

Vestibular-neck interaction and transformation of sensory coordinates.

The article considers findings and concepts on vestibular-proprioceptive interaction for self-motion perception and postural control under the form of simple describing models. It points out that vestibular-neck interaction is only a small fraction of an extended mechanism of co-ordinate transformations. This links together the different parts of our bodies, so that sensory information arising in one part of the body can be used for perceptual or motor tasks in other parts. Particular emphasis is put on the problems that arise from imperfect signal transduction in the vestibular semicircular canal systems at low stimulus frequencies/velocities. Also, a "down-and-up-channeling" principle is suggested, by which the body support is linked via coordinate transformations to the internal notion of physical space provided by the vestibular system. Furthermore, the following question is addressed: how does the brain use visual input to overcome the vestibular deficiencies, at the risk of visual self-motion illusions? Finally, a conceptual model of postural control is presented in which a proprioceptive feedback loop that links the body to its support surface is merged with a loop for postural stabilization in space.

Humans↗

PubMed1995

Galvanic vestibular stimulation for analysis of postural adaptation and stability.

Human postural dynamics was investigated in 12 normal subjects by means of a force platform recording body sway, induced by bipolar transmastoid galvanic stimulation of the vestibular nerve and labyrinth. The model adopted was that of an inverted segmented pendulum, the dynamics of postural control being assumed to be reflected in the stabilizing forces actuated by the feet as a result of complex muscular activity subject to state feedback of body sway and position. Time-series analysis demonstrates that a transfer function from stimulus to sway-force response with specific parameters can be identified. In addition, adaptation to the vestibular stimulus is demonstrated to exist, and we describe this phenomenon using quantification in terms of a postural adaptation time constant in the range of 40-50 s. The results suggest means to evaluate adaptive behavior and postural control in the erect human being which may be useful in the rehabilitation of individuals striving to regain upright stance.

Adaptation, Physiological↗

PubMed2002

Muscle power development during the first year of life predicts neuromotor behaviour at 7 years in preterm born high-risk infants.

The aim of the study was to find if neurological function during the first year of life could predict neuromotor behaviour at 7 years of age in children born preterm with a high risk. A follow-up study of neuromotor behaviour in 52 children at a mean age of 3, 6, 12 months (corrected age) and 7 years was performed. All children were born with a gestational age less than 32 weeks and/or a birthweight under 1500 g and the infants were categorised according to their medical history in the three highest categories of the 'Neonatal Medical Index' (NMI, from category I to V, from few to serious complications). In addition, neonatal cerebral ultrasound abnormalities were used to divide the infants further into the different NMI categories. At 3 and 6 months, the relationship between active and passive muscle power was measured in shoulders, trunk and legs and (a)symmetry between right and left was noted. The results at 3 and 6 months were ranged from 1 for optimal to 5 for poor muscle power regulation. At 12 months of age, a neurological examination was done with special emphasis on the assessment of postural control, spontaneous motility, hand function and elicited infantile reactions with special attention to (a)symmetry. Outcome at 12 months was expressed as percentage of the optimal score on each subcategory. At 7 years, the motor behaviour study based on Touwen's examination for minor neurological dysfunction was performed. This investigation focuses on different functions, such as hand function, quality of walking, posture, passive muscle tone, coordination and diadochokinesis. The outcome was expressed as percentage of the optimal score on the combined subcategories. The best prediction of neuromotor behaviour at 7 years was assessed with stepwise linear multiple regression, using as potential predictors perinatal factors and outcome of motor behaviour at the corrected age of 3, 6 and 12 months. At 7 years none of the children scored 100% on the combined subcategories, 15 children (29%) scored between 75% and 99%, whereas 15 children scored less than 50%. Neuromotor behaviour at 7 years could be predicted by the NMI categorisation and gender with a sensitivity of 92% (specificity 47%; positive and negative predictive value 81% and 70%). No direct relation was found between neuromotor behaviour and cerebral ultrasound classification only, days on the ventilator and/or continuous positive airway pressure, birthweight, gestational age and dysmaturity. The best predictor of neuromotor behaviour at 7 years was the combination of outcome of muscle power in shoulders and legs at 3 months and postural control at 12 months, taking into account the gender of the child (sensitivity 95%; specificity 40%; positive predictive value 80%; negative predictive value 75%).

Birth Weight↗