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PubMed2001

The effects of human ankle muscle vibration on posture and balance during adaptive locomotion.

This study investigated the contribution of ankle muscle proprioception to the control of dynamic stability and lower limb kinematics during adaptive locomotion, by using mechanical vibration to alter the muscle spindle output of individuals' stance limbs. It was hypothesised that muscle length information from the ankle of the stance limb provides information describing location as well as acceleration of the centre of mass (COM) with respect to the support foot during the swing phase of locomotion. Our prediction, based on this hypothesis was that ankle muscle vibration would cause changes to the position and acceleration of the COM and/or compensatory postural responses. Vibrators were attached to both the stance limb ankle plantarflexors (at the Achilles tendon) and the opposing dorsiflexor muscle group (over tibialis anterior). Participants were required to walk along a 9-m travel path and step over any obstacles placed in their way. There were three task conditions: (1) an obstacle (15 cm in height) was positioned at the midpoint of the walkway prior to the start of the trial, (2) the same obstacle was triggered to appear unexpectedly one step in front of the participant at the walkway midpoint and (3) the subjects' walking path remained clear. The participants' starting position was manipulated so that the first step over the obstacle (when present) was always performed with their right leg. For each obstacle condition participants experienced the following vibration conditions: no vibration, vibration of the left leg calf muscles or vibration of the anterior compartment muscles of the lower left leg. Vibration began one step before the obstacle at left leg heel contact and continued for 1 s. Vibrating the ankle muscles of the stance limb during the step over an obstacle resulted in significant changes to COM behaviour [measured as displacement, acceleration and position with respect to the centre of pressure (COP)] in both the medial/lateral (M/L) and anterior/posterior planes. There were also significant task-specific changes in stepping behaviour associated with COM control (measured as peak M/L acceleration, M/L foot displacement and COP position under the stance foot during the step over the obstacle). The results provide strong evidence that the primary endings of ankle muscle spindles play a significant role in the control of posture and balance during the swing phase of locomotion by providing information describing the movement of the body's COM with respect to the support foot. Our results also provide supporting evidence for the proposal that there are context-dependent changes in muscle spindle sensitivity during human locomotion.

Acceleration↗
PubMed2003

Dynamic and static tests of balance and postural sway in boys: effects of previous wrist bone fractures and high adiposity.

Ninety-three males aged 10-21 years undertook the Bruininks-Oseretsky balance test and two computerized posturography tests to evaluate the effects of (a) previous forearm fracture and (b) high body weight on balance and postural sway. Body composition was measured by dual energy X-ray absorptiometry. Fracture history did not affect balance measures. However, Bruininks-Oseretsky balance scores were negatively correlated with body weight, body mass index, percentage fat and total fat mass. Overweight subjects (n=25) had lower scores (P<0.05) than boys of healthy weight (n=47), supporting the view that overweight adolescents have poorer balance than those of healthy weight.

Absorptiometry, Photon↗
PubMed2006

Postulating that our neurological models for musculoskeletal support, movement, and emotional expression come from archetypal forms in early organisms.

The ability for humans, in principle, to almost effortlessly support themselves against gravity, to move with grace, and to express themselves in subtle and beautiful ways is amazing, given the number of moveable joints, variety of obstacles and intentions, and possible emotions to express. The actual mechanics are obviously astonishing but the models for these activities, in origin, must be simple. The basic hypotheses concerning these models are the following: The neurological model for the control of our musculoskeletal system is a simple support system from early organisms. This model involves a complementary relationship between the dorsal and ventral surfaces. There are three functionally distinct parts of the body, though not visually observable. These parts, named here "the director, motor, and rudder segments," are functionally distinct in optimal posture and movement. Healthy balance, posture, and movement result from their relatively independent yet coordinated actions. Forms of locomotion used by early organisms: peristalsis, lateral undulation, and dorsal-ventral undulation are present in us yet. Four frozen phases of the dorsal-ventral wave, for example, constitute four distinct postural and personality styles. I present these hypotheses together in this short paper as an introduction to a new illustration-dependent way to conceive some of our psychophysical realities. The hypotheses came from efforts to develop mental imagery to assist students in learning the Alexander technique (AT). In addition, a little known theory concerning four basic emotions and personality types, called the Fusion Theory, provided an initial concept of personality types. Four fixed postural patterns that I observed in teaching AT linked well to this personality typology. There is research that supports the use of mental imagery to affect change in body use, mostly in the sports and dance fields, but none exists addressing the specific imagery derived from these hypotheses. If these theories were confirmed, several areas could stand to benefit. Through imagery, some concepts involving musculoskeletal health could become more accessible to health-conscious and suffering individuals and give them a new way to become more connected to and responsible for their postural and mental health. Kinesiology, neurology, and psychology could develop a closer connection if research found that some aspects of posture, movement, and emotion all developed from allied origins. Specific benefits could come to the study of facial and body expression, understanding the physical basis of emotion and attitude, and understanding the experience of qualia in general.

Animals↗
PubMed2005

Long-term effects of microgravity on the swimming behaviour of young rats.

The postnatal development of sensory systems has been shown in studies over the last four decades to be influenced by experience during critical periods of development. We report here that similar experience-dependent development can be observed in the swimming behaviour of young rats reared from postnatal day 14 (P14) to P30 in the reduced gravitational field of low earth orbit. Animals flown in space when placed in the water on the day of landing maintained their head and forelimbs in a balanced posture. However, until the animals began to swim, their hindquarters showed little lateral postural control resulting in rotation about the longitudinal axis (60 degrees+/-4 deg). Such results suggest an 'unlinking' of postural control of the forequarters from the hindquarters in the early hours after landing. Similar instability seen in animals age-matched to the day of launch (97+/-7 deg) and in ground control animals (9+/-3 deg) was corrected within one or two rotations, even in the absence of swimming. Animals flown in space began to swim sooner after being placed in the water, and the duration of swimming strokes was shorter than in control animals. Motion analysis revealed a difference in the swimming style on landing day. In flight animals, the knee joint was more flexed throughout the stroke, there was a narrower range of movement, and the linear velocity of the tip of the foot was faster throughout most of the stroke than in age-matched control animals. Thus, posture in the water as well as swimming speed and style were altered in the animals flown in space. Some of these characteristics persisted for as long as the animals were followed (30 days). These included the short pre-swimming interval and short stroke duration in flight animals. These findings clearly show that an altered gravitational field influences the postnatal development of motor function. The nature of the differences between animals reared in space for 16 days and those remaining on the ground reflects an adaptation of the flight animals to the microgravity environment. The data suggest that the most fundamental of these adaptations is a resetting of the basic motor rhythm to a higher frequency.

Adaptation, Physiological↗
PubMed1981

[Body sway stabilization induced during periodic saccades (author's transl)].

Periodic saccadic eye movement has been known to cause a reduction of the body sway while standing upright in man. Then, it was studied that under what experimental conditions such a well-balanced posture could be obtained; with special references to antigravity muscle activity of the lower leg, saccades in the dark, and saccade size and frequency. Body sway was measured as the antero-posterior deviation of the center of gravity. EOG (electro-oculogram) and EMG of soleus, gastrocnemius and tibialis anterior muscles were simultaneously recorded. The results were as follws: 1) The sway reduction was observed during periodic saccades performed in frequency higher than 0.2 Hz at 30 degrees, in amplitude greater than 5 degrees at 0.5 Hz and in duration longer than a few seconds without direction specificity. 2) The effect of saccades on the body sway was classified into three types, each of which was specific to the subject. In type I and II the reduction of the body sway occurred for the component of 0.2-0.4 Hz. The sway reduction was accompanied with the increase in activity of soleus and gastrocnemius. The sway reduction was also accompanied with a forward shift of the body position in type I, but not in type II. Type III showed active discharges in soleus and gastrocnemius before saccades, suggesting that the body was being already inclined during fixation of eyes. In this type no sway reduction and no continuous shift of the body position were observed. 3) The sway reduction was observed also during periodic, voluntary rapid eye movement in complete darkness. 4) Continuous eye rotation in either direction did not affect the body sway. These results suggest that some neural activty related to the saccade may flow in the extrapyramidal system, raised the activity of triceps surae muscle directly or indirectly and stabilize the standing posture.

Adolescent↗
PubMed2003

Protective equipment affects balance abilities differently in younger and older firefighters.

INTRODUCTION: Firefighters must work on roofs, in smoky places, and on slippery surfaces while using fire-protective clothing and a self-contained breathing apparatus (SCBA), together termed "fire-protective equipment" (FPE). The aim of this study was to investigate the effects of FPE on the functional and postural balance abilities of younger and older firefighters. METHODS: The subjects were professional firefighters in age groups 33-38 and 43-56 yr. Postural balance was tested with a force platform, and functional balance was measured during walking on a wooden plank with and without FPE. RESULTS: Wearing FPE significantly impaired both postural and functional balance. Postural balance with eyes closed was more negatively affected among the older subjects than the younger ones. Among the older subjects, the mean values for mediolateral velocity were 3.4 +/- 0.8 and 4.8 +/- 2.1 mm x s(-1) without and with FPE, respectively. The corresponding figures for velocity moment were 11.4 +/- 5.1 and 20.7 +/- 15.1 mm2 x s(-1). In the younger age group, the corresponding results were 3.6 +/- 1.0 and 4.1 +/- 1.4 mm x s(-1), in mediolateral velocity and 10.8 +/- 5.0 and 13.9 +/- 8.1 mm2 x s(-1) in velocity moment. SCBA was the most significant single piece of equipment to decrease performance in the functional balance test. CONCLUSIONS: These findings should be taken into consideration for preventing balance-related injuries in firefighting and rescue work, especially for older firefighters. Furthermore, balance should be considered in developing FPE and training protocols for firefighter fitness.

Adult↗
PubMed2005

Exercise leads to faster postural reflexes, improved balance and mobility, and fewer falls in older persons with chronic stroke.

OBJECTIVES: To determine the effect of two different community-based group exercise programs on functional balance, mobility, postural reflexes, and falls in older adults with chronic stroke. DESIGN: A randomized, clinical trial. SETTING: Community center. PARTICIPANTS: Sixty-one community-dwelling older adults with chronic stroke. INTERVENTION: Participants were randomly assigned to an agility (n=30) or stretching/weight-shifting (n=31) exercise group. Both groups exercised three times a week for 10 weeks. MEASUREMENTS: Participants were assessed before, immediately after, and 1 month after the intervention for Berg Balance, Timed Up and Go, step reaction time, Activities-specific Balance Confidence, and Nottingham Health Profile. Testing of standing postural reflexes and induced falls evoked by a translating platform was also performed. In addition, falls in the community were tracked for 1 year from the start of the interventions. RESULTS: Although exercise led to improvements in all clinical outcome measures for both groups, the agility group demonstrated greater improvement in step reaction time and paretic rectus femoris postural reflex onset latency than the stretching/weight-shifting group. In addition, the agility group experienced fewer induced falls on the platform. CONCLUSION: Group exercise programs that include agility or stretching/weight shifting exercises improve postural reflexes, functional balance, and mobility and may lead to a reduction of falls in older adults with stroke.

Accidental Falls↗
PubMed2006

Force platform measurements as predictors of falls among older people - a review.

BACKGROUND: Poor postural balance is one of the major risk factors for falling. A great number of reports have analyzed the risk factors and predictors of falls but the results have for the most part been unclear and partly contradictory. Objective data on these matters are thus urgently needed. The force platform technique has widely been used as a tool to assess balance. However, the ability of force platform measures to predict falls remains unknown. OBJECTIVE: The purpose of this systematic review was to extract and critically review the findings of prospective studies where force platform measurements have been used as predictors of falls among elderly populations. METHODS: The study was done as a systematic literature review. PubMed, the Cochrane Central Register of Controlled Trials, and CINAHL databases from 1950 to April 2005 were used. The review includes prospective follow-up studies using the force platform as a tool to measure postural balance. RESULTS: Nine original prospective studies were included in the final analyses. In five studies fall-related outcomes were associated with some force platform measures and in the remaining four studies associations were not found. For the various parameters derived on the basis of the force platform data, the mean speed of the mediolateral (ML) movement of the center of pressure (COP) during normal standing with the eyes open and closed, the mean amplitude of the ML movement of the COP with the eyes open and closed, and the root-mean-square value of the ML displacement of COP were the indicators that showed significant associations with future falls. Measures related to dynamic posturography (moving platforms) were not predictive of falls. CONCLUSION: Despite a wide search only a few prospective follow-up studies using the force platform technique to measure postural balance and a reliable registration of subsequent falls were found. The results suggest that certain aspects of force platform data may have predictive value for subsequent falls, especially various indicators of the lateral control of posture. However, the small number of studies available makes it difficult to draw definitive conclusions.

Accidental Falls↗
PubMed1988

Postural adjustments induced by simulated motion of differently structured environments.

We have investigated how visual information of a scene, moving along the line of sight of a subject, affects postural readjustments made by a subject when instructed to maintain an upright posture. Two different types of stimulus patterns were presented each inducing a different optic flow field. In one case an optic flow field was induced by simulating motion of a subject relative to a wall and in the second case by stimulating motion of a subject through a tunnel. In both cases clear effects on postural balance were observed. It suggests that postural responses are invariant for the structure of the moving environment. The amplitude of the postural responses did not depend on the velocity of the simulated motion, and therefore did not depend on the absolute magnitude of the optic flow components. The amount of texture in the moving scene proved to be an important factor. In addition, it was found that the control of postural balance is not exclusively dominated by information provided by the peripheral part of the subject's visual field. Moreover, the results indicate that the divergence component in the optic-flow field alone is not sufficient to control posture in forward/backward direction.

Humans↗
PubMed1984

Dopaminergic modulation of aldosterone secretion: effect of sodium balance and postural changes.

The influence of an increased endogenous production of angiotensin II and of sodium homeostasis upon the response of plasma aldosterone to metoclopramide administration has been investigated in 5 normal volunteers. Our results show that the increase of plasma aldosterone after metoclopramide administration is independent of angiotensin II, ACTH and potassium, and that it increases even further due to the endogenous production of angiotensin II induced by postural changes. The state of sodium balance seems to influence the response of plasma aldosterone to metoclopramide administration as it occurs with other stimuli of aldosterone secretion.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

A new symmetry-based scoring method for posture assessment: evaluation of the effect of insoles with mineral derivatives.

BACKGROUND: There is a need for a validated rapid procedure for the evaluation of posture, defined as lateral balance/imbalance at the pelvic, shoulder, and neck levels. This would enable clinicians to determine the importance of symmetry in the pathophysiology of musculoskeletal disorders and to assess the efficacy of devices and treatments claiming to normalize or improve posture. In this investigation, the efficacy of such a device, a set of insoles with a hypothesized proprioceptive-like action, was evaluated through use of the described procedure. OBJECTIVES: To develop a new scoring system to evaluate body posture on the basis of symmetry and to use this scoring system to investigate the efficacy of insoles containing a combination of mineral derivatives designed to balance posture through a neurophysiological effect. METHODS: The posture score was based on the evaluation of 4 postural parameters: pelvic and shoulder lateral balance/imbalance, static shoulder rotation, and amplitude of head rotation. In the placebo-controlled study, 32 patients were tested in a double-blind fashion, either with placebo insoles or with insoles containing mineral derivatives. The same study was repeated in unblind conditions in 137 patients selected from 2 chiropractic clinics in an open-label protocol. STUDY DESIGNS: A crossover placebo-controlled, double-blind study and a multicenter, large-scale, open-label study in patients selected from chiropractic clinics. RESULTS: A basal postural evaluation in 137 patients revealed that no patient had a perfect symmetry-ie, a perfectly or nearly perfectly balanced posture. The insoles with mineral derivatives induced a highly significant and similar improvement in the postural score in both the crossover double-blind study (32 patients; 56.7% improvement) and the open-label study (137 patients; 60.7% improvement, P < 0.001). CONCLUSIONS: All patients tested and selected in chiropractic clinics exhibited asymmetries and postural imbalances according to the newly developed scoring method, and this method was successful in assessing the efficacy of insoles exerting a profound and immediate postural effect through a hypothesized neurophysiological mode of action.

Adolescent↗
PubMed1998

Strain on the gastrocnemii and hamstrings affecting standing balance on an inclined plane in spastic cerebral palsy. A study using a geometric model.

The purpose of this study was to use an non-invasive method to determine whether strain on the gastrocnemii and hamstrings influences postural balance in spastic cerebral palsy (CP). Changes in alignment during standing posture with subjects positioned on a platform that was gradually inclined were measured in 10 normal children and 11 children with CP. The changes in postural alignment were plotted and geometric models used to determine the lines where the gastrocnemii and hamstrings were maximally stretched. In this way the relationship between postural alignment and the amount of strain on the gastrocnemii and hamstrings was investigated. On the inclined platform, which caused ankle joints to become dorsiflexed as the inclination angle increased, the gastrocnemii began to be strained and the hip joints began to be flexed (trunk bent forward) at the same time. In the children with CP, the gastrocnemii were more strained by smaller degrees of inclination. Furthermore, there was one child with CP whose hamstrings were also strained on the inclined platform. We confirmed that postural balance was affected by strain on the gastrocnemii and hamstrings.

Accidental Falls↗
PubMed2006

Effect of occlusion status on the time required for initiation of recovery in response to external disturbances in the standing position.

BACKGROUND: To examine whether occlusion status contributes to improvement of postural balance. METHODS: Thirty healthy adolescents (15 males and 15 females; mean age, 20.3; standard deviation (SD) 1.6 years) with no equilibrium or stomatognathic function abnormalities were examined. Occlusion is a term meaning "jaw clenching." Occlusion status was evaluated by measuring masseter activity using the EMG system. Balancing ability was evaluated using the EquiTest system, which measures sway of the center of gravity produced by rapid movement of force plates as an external disturbance (three intensity levels). The time required for initiation of recovery after application of the disturbance was calculated by measuring displacement of the center of foot pressure. Data were compared according to occlusion status. FINDINGS: Little difference in latency was observed following a small disturbances; however, the greater the disturbance the shorter the latency with occlusion, while without occlusion, latency increased with increasing disturbance. A statistically significant interaction (P<0.001) between occlusion and external disturbance was also found. INTERPRETATION: This study suggested that occlusion contributes to maintenance of postural balance and improvement of stability when unexpected sway occurs in the standing position.

Accidental Falls↗
PubMed2006

Effect of age and sex on maturation of sensory systems and balance control.

Maintenance of postural balance requires an active sensorimotor control system. Current data are limited and sometimes conflicting regarding the influence of the proprioceptive, visual, and vestibular afferent systems on posture control in children. This study investigated the development of sensory organization according to each sensory component in relation to age and sex. A total of 140 children (70 males, 70 females; mean age 10y [SD 4y]; age range 3y 5mo-16y 2mo) and 20 adults (10 males, 10 females; mean age 30y 6mo [SD 8y 4mo]; age range 17y 2mo-49y 1mo) were examined using the Sensory Organization Test. Participants were tested in three visual conditions (eyes open, blindfolded, and sway-referenced visual enclosure) while standing on either a fixed or a sway-referenced force platform. Mean equilibrium scores for the six balance conditions showed rapid increases and maturation ceiling levels for age-related development of the sensorimotor control system. Proprioceptive function seemed to mature at 3 to 4 years of age. Visual and vestibular afferent systems reached adult level at 15 to 16 years of age, revealing differences between young males and females. Characterizing balance impairments can contribute to the diagnostic evaluation of neuromotor disorders.

Adolescent↗
PubMed2002

Subclinical cerebellar anterior lobe, vestibulocerebellar and spinocerebellar afferent effects in young female lead workers in China: computerized posturography with sway frequency analysis and brainstem auditory evoked potentials.

By computerized static posturography with sway frequency analysis, subclinical effects of lead on postural balance was examined in 29 female workers (lead workers) employed at a glass factory for 3-17 (mean 7.9) years in Beijing, China, in relation to brainstem function assessed by brainstem auditory evoked potential (BAEP). Their blood lead concentrations ranged from 26 to 79 (mean 55.7) microg/dl; ages were 21-30 (mean 28) years. Control subjects, aged 22-29 (mean 27.0) years, were 14 healthy female workers at a textile factory located in the same district. With eyes closed, power of the sway of high (2-4 Hz) and low (1 Hz or less) frequencies in lead workers was significantly larger than that in controls; with eyes open, their power of the sway of low frequency was significantly larger (p<0.05). The multiple regression analysis showed that the power of high frequency sway with eyes closed and of low and high frequencies with eyes open were significantly related to blood lead concentrations in lead workers (p<0.05). On the other hand, no significant differences in BAEP latencies between lead workers and controls were observed. The low frequency sway with eyes open was significantly correlated with the high frequency sway with eyes closed in the lead workers. The pattern of changes in postural balance suggested that the anterior cerebellar lobe, vestibulo-cerebellar and spinocerebellar afferent systems were affected asymptomatically in female lead workers; the sway of vestibulo-cerebellar and anterior cerebellar lobe types were simultaneously affected by lead. It appears that a computerized static posturography with sway frequency analysis is useful technique for assessment of subclinical lead neurotoxicity.

Adult↗
PubMed2006

Dynamic postural stability in blind athletes using the biodex stability system.

Three systems affect the upright standing posture in humans - visual, vestibular, and somatosensory. It is well known that the visually impaired individuals have bad postural balance. On the other hand, it is a well documented fact that some sports can improve postural balance. Therefore, it is aimed in this study to evaluate the dynamic postural stability in goal-ball athletes. Twenty blind goal-ball players, 20 sighted and 20 sedentary blind controls were evaluated using the Biodex Stability System. Three adaptation trials and three test evaluations (a 20-second balance test at a platform stability of 8) were applied to the blind people, and to the sighted with eyes open and closed. Dynamic postural stability was measured on the basis of three indices: overall, anteroposterior, and mediolateral. Means of each test score were calculated. The tests results were compared for the blind athletes, sighted (with eyes open and closed) subjects, and sedentary blind people. There were significant differences between the results of the blind people and the sighted subjects with regards to all of the three indices. Although the stability of goal-ball players was better than sedentary blinds', only ML index values were statistically different (4.47 +/- 1.24 in the goal-ball players; 6.46 +/- 3.42 in the sedentary blind, p = 0.04). Dynamic postural stability was demonstrated to be affected by vision; and it was found that blind people playing goal-ball 1 - 2 days per week have higher ML stability than the sedentary sighted people.

Adolescent↗