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PubMed2002

Transient dystonias revisited: a comparative study of preterm and term children at 2 1/2 years of age.

Minor neurological dysfunctions (MND) have frequently been reported as an outcome of preterm birth. Behavioural and learning difficulties are a known feature, but coordination problems are especially described in preterm infants at later ages. All preterm infants in our study were born with a gestational age of <32 weeks and a birthweight of <1500 g. The aim of the study was to determine if in a normal clinical situation, children at risk for developing coordination problems could be detected by focusing particularly on their spontaneous, although elicited, motor performance. Forty-two children of 2 years 6 months of age were studied of whom 25 were 'low-risk' preterm and 17 were born at term. All children had been followed up since birth. In a structured, free-field situation the quality of body rotation, spontaneous reaching-out, and manipulation during parts of the Bayley Developmental Test were observed and videotaped. Body rotations were scored on a 2-point scale, and arm and hand functions on a 3-point scale. Most preterm infants showed non-optimal body rotations and borderline or non-optimal arm and hand functions in contrast to most term children. A clear connection was found between less optimal body rotations and poor arm and hand functions. Retrospectively, poor arm and hand functions at 2 years 6 months seemed to be related to those at 39 weeks. At the age of 39 weeks a clear relation had been found between poor postural control (many preterm infants could not sit independently) and earlier hyperextension of the trunk at 18 weeks and quality of arm-hand functions. In the present study at 2 years 6 months a correlation with the former hyperextension could no longer be found, but there was a significant relation between poor trunk rotation and arm and hand function and the earlier arm and hand functions at 39 weeks.

Arm↗

PubMed2001

Relative contribution of ankle and hip muscles in regulation of the human orthograde posture in a frontal plane.

It was investigated, whether the postural regulation in the frontal plane takes place mainly at the hip or at the ankle level. The elimination of ankle torque was achieved by providing a point support in the frontal plane. (Two boards were attached to subject feet, below each board a metal pipe 2 cm diameter was fixed, so, the subject stood on contrivances resembling 'skates'). The lateral displacements of breast and hip, the angle of 'skates' tilt and the characteristics of frontal stabilogram and electromyogram of two ankle muscles (m. peroneus and m. soleus) were compared in two situations: (1) during normal standing; (2) under the conditions of the exclusion of ankle torque from postural control. During normal standing the body behaved as two-link inverted pendulum. Transition from normal standing to standing on free 'skates' produced changes in the kinematics of body movement. Under the conditions of ankle torque exclusion (free 'skates') breast and hip of a subject moved in a frontal plane as a single unit (one-link inverted pendulum). During standing on free 'skates' the electromyographic activity of m. peroneus and m. soleus was the same as during normal standing (approximately 70-100 microV).

Adult↗

PubMed2001

Biomechanics of slips.

The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or 'friction used/achievable' during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety.

Accidental Falls↗

PubMed2004

Postural role of lateral axial muscles in developing bottlenose dolphins (Tursiops truncatus).

Foetal dolphins (Tursiops truncatus) are bent ventrolaterally, such that the tailflukes and lower jaw are juxtaposed. The lateral flexibility required en utero may compromise the efficiency of the dorsoventral oscillations required of the swimming neonate. The m. intertransversarius caudae dorsalis (IT) is the most laterally placed epaxial muscle. Bilateral contractions of the IT could limit lateral deformations of the flexible tailstock of the early neonate. We test the hypothesis that the IT is functioning as a postural muscle in neonates by examining its morphological, histological and biochemical properties. The neonatal IT has a relatively large cross-sectional area and bending moment, as well as a large proportion of slow-twitch fibres and elevated myoglobin concentrations. Our results demonstrate that the IT is functionally capable of performing this specific postural function in neonatal dolphins. In later life-history stages, when postural control is no longer needed, the IT serves to fine-tune the position of the tailstock during locomotion. The changing function of the adult IT is concomitant with changes in morphology and biochemistry, and most notably, with an increase in the proportion of fast-twitch fibres. We suggest that these changes reflect strong selective pressure to improve locomotor abilities by limiting lateral deformations during this critical life-history stage.

Animals↗

PubMedDate not supplied

Posturography findings in workers exposed to industrial solvents.

Postural control was investigated by static posturography in 18 workers exposed to industrial solvents, 9 patients with psycho-organic syndrome due to industrial solvent exposure, and 52 controls. Both groups of exposed subjects showed larger sway areas with eyes open as well as closed, compared with the controls. No differences were found in the Romberg quotient (the relationship between sway areas with eyes closed/open). The correlation between static posturography and the otoneurological test battery was positive for the visual suppression test in the styrene group. In the industrial solvent group no significant correlations were found. The visual suppression test and some auditory tests were pathological in the exposed groups. The otoneurological test battery--especially the visual suppression test and static posturography--seems to contribute in the assessment of solvent related CNS lesions.

Adult↗

PubMed2005

Effect of menopause on melatonin and alertness rhythms investigated in constant routine conditions.

Although studies have reported the effects of the menstrual cycle on melatonin rhythmicity, none has investigated the effects of menopause on the melatonin rhythm. The circadian rhythm in melatonin and its relationship to subjective alertness was investigated in pre- and postmenopausal women under constant routine conditions (controlled posture, dim lighting, calorie intake, temperature, and prolonged wakefulness). Eleven healthy pre-menopausal (42+/-4 yr) and 10 postmenopausal women (55+/-2 yr) participated in the study. Salivary melatonin samples and subjective measures of alertness and sleepiness were assessed hourly during the 22 h constant routine protocol. Postmenopausal women had a significantly earlier melatonin acrophase (1.1+/-0.5 h clock time in decimal h; mean+/-SEM, p<0.05) compared to the pre-menopausal women (2.3+/-0.3 h). There was no significant difference between melatonin onset and amplitude between the pre-menopausal and postmenopausal women. Self-rated alertness declined in both study groups as the length of sleep deprivation increased. Melatonin onset preceded the onset of self-rated sleepiness in both groups. The time interval between melatonin onset and the onset of sleepiness and alertness offset was significantly greater in the postmenopausal women compared to the pre-menopausal women. In conclusion, under controlled experimental conditions the timing of the melatonin rhythm was advanced in postmenopausal women altering its phase relationship to subjective alertness and sleepiness.

Adult↗

PubMed1995

Reversible and irreversible neuronal injury induced by intrahippocampal infusion of the mGluR agonist 1S,3R-ACPD in the rat.

Metabotropic glutamate receptor (mGluR)-induced neuronal injury in the brain was further investigated in the rat. The highly selective mGluR agonist 1S,3R-1-aminocyclopentane-1, 3-dicarboxylic acid (1S,3R-ACPD) was infused stereotaxically into the left dorsal hippocampus of adult rats. Control (2 microliters saline injected) rats had minimal tissue injury that was confined to the area around the injection site. In contrast, a dose of 250 nmol/2 microliters 1S,3R-ACPD produced a moderate number of swollen and injured cells in polymorphic, pyramidal and molecular layers of the injected hippocampus which was observed at 4 and 8 h post-injection. However, at 24 h few injured or necrotic cells were found. A dose of 1000 nmol/2 microliters 1S,3R-ACPD produced severe cellular injury in polymorphic, pyramidal and molecular layers of the hippocampus at 4, 8, or 24 h. At 24 h after this higher dose of 1S,3R-ACPD, a number of necrotic cells (i.e. pyramidal neurons of area CA1) were found. Both doses of 1S,3R-ACPD produced seizures in animals that were characterized by multiple episodes of wet dog shakes, staring, immobility, facial automatisms, rearing, bilateral forelimb clonus, and loss of postural control. These data support a possible role for excessive mGluR activation in pathological states of convulsions and neurodegeneration.

Animals↗

PubMed2004

[Influence of physical activity on postural capacities of elderly: effect of time of training].

OBJECTIVE: The aim of this work was to define the influence of physical activity on static postural control of two groups of elderly people qualified as "non-active" for the first one and "active" as far as the second group is concerned. The first group practised a physical activity during 3 months whereas the second group practised during 9 months. SUBJECTS AND METHOD: The two groups were composed of 21 subjects of 73 years-old and 10 subjects of 74 years-old. They were characterised by stabilometric data of surface, lengths and spontaneous sway in the lateral (X) and antero-posterior (Y) axis. The evaluations were separated by a period of 12 months and realised with open eyes and closed eyes on firm floor. RESULTS: The statistical analysis showed a significant difference of both groups on surface data in closed eyes condition (P < 0.04). CONCLUSION: The methodological conditions of the study and the heterogeneity of this kind of population could explain the lack of significant effect of the protocol. Data showed different postural adaptations between the two groups after training for a part of stabilometric parameters. Those data focused on the interest of the individualisation of training for elderly people. This approach may well favour the well-being and functional autonomy of this population.

Aged↗

PubMed2000

Influence of vibration to the neck, trunk and lower extremity muscles on equilibrium in normal subjects and patients with unilateral labyrinthine dysfunction.

To investigate the role of proprioceptors of different skeletal muscles in postural control, in normal subjects and patients with unilateral labyrinthine dysfunction (ULD), the effect of vibration on these muscles was studied by postulography. The subjects comprised 59 normal subjects and 12 patients with ULD due to resection of acoustic tumours. Sagittal body sway was observed during vibration to the triceps surae, tibialis anterior and upper dorsal neck muscles. No significant change in sway was observed in the frontal plane in normal subjects. Significant differences between normal subjects and patients were found on stimulation of the muscle groups of triceps surae and biceps femoris during vibration. In patients with ULD, vibration to the dorsal neck muscles caused a deviation towards the diseased side. It can be speculated that the upper dorsal neck muscle plays an important role in maintaining the body balance in the frontal plane in patients with ULD. On the other hand, the lower extremity muscles, especially the muscles on the dorsal side of the body, play a significant role in adjusting the standing posture in the sagittal plane.

Adult↗

PubMedDate not supplied

Prevention of ankle sprains.

Two different methods for the prevention of ankle joint injuries in soccer were tested. Coordination training on an ankle disk improves functional stability and postural control, whereas an orthosis provides mechanical support. Both techniques reduce the frequency of ankle sprains in soccer players with previous ankle problems. The orthosis is an alternative to taping, and can be used during the rehabilitation period after injury or when playing on uneven ground. Coordination training on an ankle disk ought to be included in the rehabilitation of ankle injuries to prevent functional instability. It may also be done prophylactically by players with previous ankle problems in order to break the vicious circle of recurrent sprains and feeling of giving way.

Ankle Injuries↗

PubMed2002

Activity level and balance in subjects with mild Alzheimer's disease.

To clarify if Alzheimer's disease has an impact on activity level and postural control, we examined 17 elderly diagnosed with mild Alzheimer's disease (MMSE scores 21-29) and 18 age- and gender-matched healthy controls (MMSE scores 27-30) using the Frenchay Activities Index, Bergs Balance Scale, Timed Up & Go and Walking in a Figure of Eight. Mild AD subjects were less active and had lower scores on Bergs Balance Scale, performed Timed Up & Go in longer time and took more steps outside the Figure of Eight, as compared to healthy elderly. This study shows that motor performance is affected already at mild stages of Alzheimer's disease and also that functional performance other than gait may also be impaired.

Aged↗

PubMed1991

[Photoelastic studies of the position of plantar pressure center and its changes at standing upright: analysis on Down syndrome].

With a photoelastic method, contact pressure patterns between foot and the floor surface were recorded, occasionally for one minute. The aim of this study is to evaluate the development or maturity of postural control. As a clinical model to be tested, Down syndrome characterized by marked muscular hypotonicity was chosen for quantitative analysis. The following results were obtained; (1) the center of contact pressure is shifted significantly forward in Down syndrome, (2) the position tends to move forward on the left side in both normal and Down syndrome groups, and (3) there was no distinctive laterality of weight loading on either side. Flaccidity of ankle joint movements such as abnormal eversion was indicated by a special parameter, which was obtained for the first time by this method.

Child↗

PubMed1993

[Effects of eye tracking stimulation on movements of the body's center of gravity and the head in elderly subjects (second report)].

This study was designed to investigate the effects of eye movement (smooth pursuit and saccade) on the upright standing postural control, and to compare movements of the body's center of gravity (CG) and the head between an elderly group and a young control group. The elderly group consisted of 28 healthy subjects aged 60 to 79 years, the young control group of 11 healthy subjects aged 20 to 39 years. Visual conditions consisted of fixation on a spot fixed target, pursuit of a 0.1 Hz sinusoidally horizontally moving target and fixation on a 0.1 Hz alternately changing right and left target. The parameters analyzed were total lengths of the locus traced by CG and head movement, the area which was a multiplication of maximum widths in the X and Y directions, ratio of the antero-posterior component to the lateral component (Y/X ratio), averaged divisional frequencies calculated in the range between 0.0195 and 1 Hz, and the ratio of head movement to CG movement regarding total lengths and area. The results were as follows: 1) Body sways in the elderly and young groups were similarly affected by eye movements. The results suggest that inputs from the extraocular muscles produce an asymmetry in the tonus of antigravity muscles and an increase in lateral body sway, and that different visual conditions elicit different sensations of perturbation, which cause characteristic postural responses. 2) Head movement was relatively larger than CG movement in the elderly group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2001

Analysis of postural perturbation responses.

People with cerebellar ataxia lack lower limb coordination and dissipate sway motion slowly and inefficiently after a posture perturbation. We report a practical and low-cost "human resonance frequency test" for both laboratory and clinical use to quantify progress in balance and cerebellar rehabilitation. We assumed that the center-of-pressure (COP) oscillation rate of decay following a standing posture perturbation is directly related to resonance frequency; a more rapidly dissipating COP oscillation about the position of equilibrium indicates, by definition, more efficient postural control. We hypothesized that following successful physical rehabilitation, people with cerebellar degeneration will have a faster rate of decay of the COP response to an external perturbation. Because the COP is modulated by a synergy of trunk and lower limb motion strategies, COP decay rate may be a useful measure of lower limb coordination in people with cerebellar ataxia. The method was applied to three subjects with cerebellar ataxia before and after rehabilitation; there was good agreement between the calculated COP decay rate and conventionally used gait stability parameters providing pilot data for this simple approach.

Adaptation, Physiological↗

PubMed1996

Analysis of toe pressures under the foot while dynamic standing on one foot in healthy subjects.

Dynamic balance is a crucial element in performing many activities of daily living. The one-leg stance test is a valuable test for balance impairment. The aim of the present study was to assess the relationships between body sway and toe pressure for dynamic balance test of one-leg standing on a perturbation platform. The subjects were 15 volunteers (six males and nine females, age = 21.1 +/- 1.8 years). The instrument used for evaluation of balance was the Balance System, whose software provides information on the subject's stance balance through calculation of two main variables: 1) body sway parameters (cm) and 2) peak pressure (percent of body weight/cm2) under the toes. The Balance System includes actuators which move the foot platform back and forth (+/- 40 mm perturbation at 0.25 Hz) at an average velocity of 20 mm/sec. The subjects were asked to balance on each leg for 20 seconds. The trials were repeated on the opposite foot after 5 minutes of rest. The dynamic postural control induced by low frequency perturbation in the anterior/posterior direction used the ankle strategy. Body sway was more significantly correlated with the peak anterior/posterior sway component than with lateral sway (p < 0.01). The peak pressure value of the great toe was significantly greater (p < 0.01) than the sum of the peak values of the other four toes for both sides. The study indicates the importance of the strength of the toes and somatosensory information from the sole and ankle during the dynamic one-foot standing balance as goals in rehabilitation for poor balance.

Adult↗

PubMed1995

Early activation of arm muscles follows external perturbation of upright stance.

Grasping, counterbalancing and protective arm movements are an important defence against external postural perturbation, but are commonly constrained in studies of postural control. We measured muscle activity at the shoulder, and the lower leg, during unconstrained responses to platform translation. Results revealed very early activation in shoulder muscles, similar in timing to the 'automatic' ankle responses. The arm activation occurred even when the reaction provided no immediate defence against destabilization but would appear to be more than a 'startle' response, since the activation was scaled to the perturbation magnitude and persisted even when perturbations were expected. The arm activation would appear to be driven from a remote sensory source, since there was negligible loading or stretch of the arm muscles.

Adult↗

PubMed2000

Spectral analysis of adult dancers' sways: sex and interaction vision-proprioception.

In subjects of both sexes with or without dance training, dependence on vision and proprioception for postural control was studied by destabilizing these cues on a free seesaw. Fast Fourier transform processing allowed spectral frequency analysis of the platform sways recorded by an accelerometer. Two frequency bands of the total spectral energy were used: the lower (0 - 2 Hz) and the higher (2 - 20 Hz) frequency bands. Dancers were significantly less dependent on vision but use more proprioception than untrained subjects. Professional dance training appears to shift sensorimotor dominance from vision to proprioception, and this evolution seems more marked for males than females. Female and male dancers had similar dynamic performances, but for males, the better neuromuscular coordination may be associated with biomechanical factors.

Adult↗

PubMed1981

Central distribution of octavolateral afferents and efferents in a teleost (Mormyridae).

The central distribution of afferents from individual eight nerve branches (N VIII) and mechanical lateral line end organs in mormyrid fish are described. Afferents were labeled with horseradish peroxidase (HRP) placed on the cut ends of the different N VIII branches and the anterior and posterior lateral line nerves. Descending, tangential, and magnocellular nuclei receive input almost exclusively from the utriculus and canals. Nucleus octavius receives afferents from the lateral line nerves and all N VIII branches, with one part receiving exclusive and bilateral input from the sacculus. Afferents from both lateral line nerves and all N VII branches, except the sacculus, end in eminentia granularis. Afferents from each of the two lateral line nerves and from each of three otolith branches of N VIII end in different regions of the anterior lateral line lobe, with some areas of overlap. Behavioral studies in other families of fish indicate that the utriculus and canals are critical for postural control, whereas the sacculus and possibly the lagena are concerned with hearing. Such findings, together with the results of this study, suggest that mormyrids and perhaps other fish possess separate auditory and vestibular centers within the octavolateral area. The HRP method also shows the cell bodies and axons of octavolateral efferents. N VIII and lateral line efferents arise from a common nucleus, and the central course of their axons parallels that of facial motoneurons. Axons of efferent cells divide to supply two or more branches of N VIII and some axons supply both lateral line and N VIII end organs.

Afferent Pathways↗