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Biomedical subjects

B Bril

Publications and source records attributed to B Bril.

11 recordsLinked to original sources
PubMed2006

Stroke frequency and arm coordination in front crawl swimming.

This study aims to determine whether the arm coordination observed at different stroke rates (SR, number of arm stroke cycles per minute) differs according to the level of expertise. Thirteen non-expert (G(NE)) and 14 expert (G(E)) swimmers swam crawl five 25-m lengths at five stroke rate values: 35, 40, 45, 50, and 55 cycles.min(-1). Results show that the pattern of 45 % of G(NE) switched from the catch-up (a lag time is performed between the propulsive phases of the two arms) to the superposition coordination mode (both arms pushing simultaneously during a short period of the cycle) between 45 and 50 cycles.min(-1). Patterns of 62.4 % of G(E) switched in the same way between 50 and 55 cycles.min(-1). Significant differences in coordination patterns were found between G(NE) and G(E) only when SR was set at 45 cycles.min(-1). As non-expert swimmers seldom produce the superposition mode, but adopt this pattern when required to swim at high stroke rate values, it is suggested that this coordination mode is an emergent property of the movement.

Adult↗
PubMed2000

Acquisition of upper body stability during walking in toddlers.

This study examines the development of head and trunk movements in toddlers as they begin to walk independently. The data are from a longitudinal study of 7 infants observed from the onset of walking over a period of 46-80 weeks. Head and trunk rotations were measured in the frontal and sagittal planes together with global gait parameters (progression velocity, step cadence, length and width, duration of double support phase). The results showed that during the first weeks of walking head and trunk oscillations significantly decreased, indicating that considerable progress is made in upper body stabilization. Dramatic changes in global gait parameters also occurred at this time. After this first period of rapid changes, gait parameters continued the same developmental trend but with slower changes. The close relation between gain in head and trunk stability and improvement in walking efficacy is discussed on the basis of the individual developmental trends.

Child Development↗
PubMed1998

The build-up of anticipatory behaviour. An analysis of the development of gait initiation in children.

This study analyses the anticipatory postural adjustments during the gait initiation process in children aged 2.5, 4, 6 and 8 years. In adults, anticipation during gait initiation includes a shift in the centre of foot pressure (CP) both backwards and towards the stepping foot. Backward displacement and the duration of the anticipation phase covary with the gait progression velocity reached by the subject at the end of the first step. In the present study, the children walked on a force plate that allowed us to calculate the acceleration of the centre of mass and the displacements of the CP. The results showed three main characteristics of the development of anticipatory behaviour: (1) The occurrence of anticipatory displacements of the CP increased progressively with age. Systematic backward anticipation was found for all children except one of the youngest, whereas the lateral displacement was systematically observed later, in the 6-year group; (2) the amplitude of the spatial parameters showed a significant increase with age; (3) contrary to the adult, the amplitude of the backward shift did not covary with the forthcoming velocity in the youngest groups. This covariation became significant at 6 years and remained significant at 8 years. The results showed that even if anticipatory behaviour was present in 2.5-year-old children it is only later that the child is able of more accurate tuning of feedforward control, probably due to better control of the overall postural adjustments.

Age Distribution↗
PubMed1998

Development of postural control of gravity forces in children during the first 5 years of walking.

The aim of this work was to propose developmental indexes relative to the control of balance and gravity forces, using force-plate data, for children in their first 5 years of independent walking. The first part of this paper is devoted to the definition of an index to quantify postural capacity during walking. Based on the assumption that the vertical acceleration of center of mass (CM) reflects the capacity of muscular forces between the head-arms-trunk and the stance leg segments to control the external forces, the value of the CM vertical acceleration at foot contact is proposed as a developmental index of the postural capacity of the child to control gravitational forces. This index was analyzed longitudinally in five children, over the course of eight experimental sessions. The children were examined during their first 5 years of independent walking (for a total of 457 step sequences). The covariation between the CM vertical acceleration at foot contact and the gait velocity was considered as a second index characterizing the development of coordination between the postural and dynamic requirements of body progression. From these indexes it was established that the postural capacity needed just to control balance with the leg muscles was not attained before 4-5 years of independent walking, i.e., at about 5-6 years of age.

Acceleration↗
PubMed1998

Head coordination as a means to assist sensory integration in learning to walk.

After a brief presentation of the development of free walking interpreted as learning dynamical equilibrium, the problem of sensory integration in the process of walking development is discussed. A critical review of the role of vision in the development of posturo-locomotor task is presented, along with recent test results on the development of the vestibular system. A final section presents the development of head stabilization and coordination as a necessary means to assist sensory integration. It is suggested that if sensory information is necessary to enhance posturo-locomotor skills, a good mastery of walking is in turn necessary to increase the efficiency of sensory integration.

Head Movements↗
PubMed1995

Trunk and head stabilization during the first months of independent walking.

This study measured the rate of acquisition of head and trunk postural control during the two early developmental periods of independent walking, as defined by global gait parameters. Gait parameters were observed longitudinally in four children. The maximum angular deviations of the trunk and head oscillations were computed in the frontal and sagittal planes. These decreased most dramatically during the first 10-15 weeks of independent walking, during the same period when global gait parameters changed rapidly. This head and trunk stabilization may be a fundamental process that help to maintain equilibrium during walking, and may be a necessary step prior to the development of fine posturo-motor control.

Analysis of Variance↗
PubMed1992

Postural requirements and progression velocity in young walkers.

This article describes developmental changes in gait velocity and relates these changes to gait parameters that index postural stability (step width and lateral acceleration) and two components of velocity (cadence and step length). Five children were observed longitudinally over a 2-year period after onset of independent walking. Their range of speed increased threefold in the first 6 months of independent walking and then remained constant. In contrast, step width decreased approximately twofold. Whereas in adults, cadence and step length contribute approximately equally to speed, when infants first begin to walk independently, increase in velocity is due mostly to increased step length. After 5 months of independent walking, the pattern reverses, and increase in velocity is due primarily to increased cadence. The pattern remains constant over the next 18 months. From a developmental point of view, the data lead us to interpret early walking (the first 5 months) as a process of integration of postural constraints into the dynamic necessities of gait movement. A second phase, beginning after 4 to 5 months of independent walking, is considered to be a tuning phase characterized by a more precise adjustment of the gait parameters.

Journal Article↗
PubMed1991

[How does a child modulate his progression speed during the first 18 months of independent gait?].

Our results clearly suggest that during the 18 months following onset of independent walking, toddlers undergo a two-stage development process. Firstly, up to the sixth month of independent walking, there is a striking evolution of all the gait parameters analysed here. The correlation between velocity and length of steps is highly significant. Those data lead to interpret early walking as a process of "integration" of postural constraints to the dynamic necessity of gait movements. In the second stage, velocity becomes highly correlated with foot's frequency. It appears to be more of a turning phase of all the gait components.

Child Development↗
PubMed1989

Analysis of the transition from upright stance to steady state locomotion in children with under 200 days of autonomous walking.

The aim of this paper was to study, from a developmental perspective, the transient phase of gait during the period between the standing posture and the achievement of steady state gait, using temporal and biochemical parameters. Eight children who had been walking autonomously for 90 to 200 days were observed. A total of 64 sequences of steps were analyzed. A sequence of steps began with the child standing still and was executed on a large force plate. From the determination of the instantaneous velocity of center of gravity results establish that, unlike adults, progression velocity in children end of the first step, but after two to four steps. The gait initiation process does not depend on the steady state velocity, but results from an initial fall. The duration of the movement up to the end of the first step is independent of the progression velocity but depends only upon the body mass and moment of inertia of the children.

Journal Article↗
PubMed1988

[Why do children walk when falling down while adults fall down in walking?].

Some posturo-dynamical features of early gait have been studied in 5 children a few weeks after onset of independent walking and are analysed in comparison with adult gait. During the single support phases, the vertical acceleration of center of gravity of the child is negative and remains positive only during the double support phases. For the adult, the vertical acceleration of the center of gravity is positive before the time of heel contact. During the single support phases of the independent gait, the child does not have the same postural capacity to maintain his balance with respect to the gravitational forces and control of the vertical position of his center of gravity is different of the adult.

Acceleration↗