The influence of classical dance training on preferred supporting leg and whole body turning bias.

A rightward turning bias has been more frequently noted during adult classical dance practice than during spontaneous rotations. Training could play a role in inducing a preferred direction. We observed the preferred direction for executing four spontaneous whole-body full turns (pirouettes), with eyes open or closed, in pre-pubertal untrained girls and classical dance students. Of untrained girls, 58% showed a leftward turning bias (LTB) and 42% a rightward turning bias (RTB), independently of vision, lateral preferences, and supporting leg. Only one dancer showed a consistent LTB while the majority showed a RTB, with a tendency to use the left leg to turn towards the right. These results suggest that the role of the vestibular and visual systems is minimal for untrained girls, and suggest a training influence for dancers. The dance students' choice of a supporting leg for turning may exploit some biomechanical properties facilitating the pirouette.

Vestibular memory-contingent whole-body return: brave exocentered dancers.

A whole-body, self-driven return from passive rotation (90 degrees to 270 degrees ) test was executed by male and female subjects, and by professional female ballet dancers. To accomplish the return task, subjects were free to use the egocentered reference frame (inversion) or the exocentered one (completion). The results show that with inversion all kinetic parameters were reproduced, whereas the completion performance was highly variable. Although inversion was the default strategy, female subjects used more completions than male subjects, and female dancers still more, although not more accurately. The high variability noted in completion shows a deficiency in integrating vestibular signals for updating the egocentric representation of an external target during passive body rotations, even in dancers. Furthermore, with completions after 180 degrees stimuli, the results suggest that both ego- and exocentered reference frames cannot be used simultaneously.

Unilateral jump behavior in young professional female ballet dancers.

In the field of dance, lateral body actions should be differently influenced by training. Classes should develop symmetrical jump behavior by the alternate working of the two body sides. In contrast, asymmetrical training effect linked to hemispheric laterality should be also expected. Indeed, for aesthetic reasons, the preferred led has to give the jump direction while the other leg has to carry out the impulsion during take-off. In addition, and for functional reasons, the preferred leg also has to ensure a soft landing and to avoid imbalance upon landing. To address the question, we studied ten professional right-footed female ballet dancers in a unilateral experimental task: the maximal vertical jump (MVJ). The MVJ height was compared for each leg in ten trials. In addition, the side of the leg usually involved in a choreographic bilateral task was determined. All these right-footed dancers selected their left leg as the impulsion leg for the choreographic jump so as to reserve the right leg for the expression of the artistic gesture linked to emotional laterality. However, ANOVA did not show differences between the right and left legs in MVJ. In these young ballerinas, jump actions of the two body sides seem to develop symmetrically by class training effects.

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.

The contribution of vision in dynamic spontaneous sways of male classical dancers according to student or professional level.

We investigated the involvement of vision in the regulation of dynamic equilibrium in male children and young adults performing a physical activity requiring a high level of spatial skill: self-induced body sways of ballet dancers on a free unstable platform, 45 professional male dancers (Paris Opera) participated in the study. They included two student groups (beginners and confirmed) and two performer groups (adolescent and adult). They maintained their equilibrium on the platform under different visual and position conditions. The displacement of the seesaw platform were calculated from accelerometer measures. Fast Fourier transform processing of stabilograms allowed spectral frequency analysis. The total spectrum energy and the energies of the three frequency bands (0-0.5 Hz, 0.5-2 Hz, 2-20 Hz) were determined. For all groups, ANOVA indicated that values were higher for eyes-closed than for eyes-open conditions. The visual dependence differed according to age: for 14-year-old students the postural control for dynamic equilibrium was less visually dependent than for 11-year-old students. The 18-year-old dancers, although professional, were more dependent on vision than 14-year-old student dancers. These 18-year-old dancers were still adolescent because they had recently undergone growth acceleration which could disturb their proprioceptive references and internal body representations. Thus, visual input may dominate over the other sensory inputs in the regulation of postural control.

Visual contribution to self-induced body sway frequencies and visual perception of male professional dancers.

We studied the degree of dependence on vision, for postural control and for perception, among male adult dancers and untrained subjects. First, body sways were analyzed on a free seesaw platform. Fast Fourier transform processing allowed spectral frequency analysis of the platform sways recorded by an accelerometer. Secondly, a visual dependence test, the rod and frame test (RFT) was used. Professional dancers were significantly more stable and less dependent on vision for postural control and for perception than untrained subjects. Presumably, professional dance training strengthens the accuracy of proprioceptive inputs and shifts sensorimotor dominance from vision to proprioception. For the dancers, there was interaction between the RFT visual dependence and the visual control of posture: the less visual-dependent they were for the RFT, the more stable they were in dynamic balance conditions.

Sex-linked differences in equilibrium reactions among adolescents performing complex sensorimotor tasks.

Equilibrium reactions were compared between male and female adolescents (prepuberal and puberal), classified into two groups: those who had previously learned complex motor tasks (dance or acrobatics) and those with no particular training. Subjects stood (eyes open or eyes closed) on a free seesaw platform, the displacements of which were calculated from accelerometer measures. They were instructed to maintain a vertical position with their frontal plane either parallel (to measure antero-posterior oscillations) or perpendicular to the axis of the platform (to measure lateral oscillations). Girls had a better stability than boys as shown by the smaller displacement of their center of gravity. Untrained subjects, irrespective of sex, were the least stable. Subjects trained in acrobatics were more stable than dancers. Differences related to sex can be attenuated by physical training involving equilibrium exercises which suggests that moderate sustained training could reduce the incidence of falls in aged persons and in professionally exposed workers.

The effects of maturation on self-induced dynamic body sway frequencies of girls performing acrobatics or classical dance.

We investigated the effects of maturation on the dynamic body sways of healthy girls. Prepubertal and postpubertal girls practising professional physical activities requiring a good ability to maintain equilibrium (acrobats and dancers) were asked to stand on a free seesaw platform and the results compared to those for untrained age-matched girls. This platform (stabilometer) allows self-induced body sways. Stabilograms were obtained by a double integration of the angular acceleration from the recordings of the platform sways made with an accelerometer. Fast Fourier transform processing of stabilograms allowed spectral frequency analysis. The total spectrum energy and the energies of three frequency bands (0-0.5 Hz, 0.5-2 Hz, 2-20 Hz) were determined. ANOVA showed that, for all groups of different equilibrium activity and independent of visual input, prepubertal girls had higher energy values than postpubertal girls in the 0- to 0.5-Hz band whereas the opposite was true for 0.5- to 2-Hz band. Ballet dancers were more dependent than acrobats on visual inputs for the regulation of their postural control but were less dependent than untrained girls at both ages. Maturation seemed to shift body sways towards higher frequencies and the utilization of the cues of postural control was different according to the type of equilibrium activity practised by the subjects.

Spectral frequency analysis of dynamic balance in healthy and injured athletes.

Different neurophysiological circuits underlie the various frequencies of the body sway for the regulation of human upright posture. Servo-controlled platforms allowed experimental studies about latency responses after a sudden external disturbance but power frequency repartition during spontaneous dynamic equilibrium has rarely been examined. The purpose of the present study was to examine the zone of sway frequency assigned to proprioceptive afferences from muscular, articular and tendinous receptors in healthy and injured subjects standing on an unstable and minimal area. Dynamic balance conditions were realized by asking athletes to stand up on a seesaw (stabilometer). The recordings (stabilograms) were monitored by means of an accelerometer. Their power spectra were obtained by a fast Fourier transform process. A first study was conducted in order to specify the contribution of articular receptors of the ankle in the regulation of spontaneous dynamic equilibrium of five soccer players with unilateral injured ankle (IA). The balance parameters in lateral sways were measured in monopodal stance on the healthy ankle (HA) comparatively to IA. The stabilogram was longer (P < 0.05), the total energy of 2-20 Hz band (P < 0.01) higher in the IA (1074 +/- 111 mm and 53 +/- 8 V2) than in the HA (836 +/- 150 mm and 36 +/- 8 V2). A second study analyzed the contribution of knee articular receptors involved in the reflexes of antigravity extension. We assessed during bipodal stance the anteroposterior sways of five basketball players with injured knee (IK) and 3 with healthy knee (HK) in eyes-open and eyes-closed situations.(ABSTRACT TRUNCATED AT 250 WORDS)

[Simple locomotion and during load carrying in pregnant women]. / Etude de la locomotion simple et lors du transport de charge chez la femme enceinte.

There have been few studies of the way women walk in pregnancy, though some of the causes of low back ache of which they complain have only been partially worked out. This is why this study has been carried out on ten women between the third and eighth month of pregnancy. The speed at which they walk and the parameters of the gait as well as the localization of the centre of gravity when keeping upright have been measured in these pregnant women as well as in twenty control women of the same age. The results show that the speed at which they walk whether with or without carrying a weight usually is identical at the beginning and the end of pregnancy. When walking normally the size of the steps taken are no larger in pregnant women than in the control patients (p less than 0.05). Though the results are not statistically significant the rhythm of the steps is faster as well as their being a reduction in the length of the steps between the third and eighth month of pregnancy. When carrying a weight the length of the steps does not change greatly with pregnancy (p less than 0.05) and it would seem therefore to be a good way of assessing the changes that locomotion undergoes in pregnancy. The fact that women do not walk faster or slower can give evidence that they adapt to the change in posture that happens in pregnancy and they make the best possible biomechanical use of the parameters of walking in order to economise total energy output of the organism.(ABSTRACT TRUNCATED AT 250 WORDS)

[Exercise and pregnancy. Study of the change in heart rate in pregnancy when performing standardized moderate exercise]. / Port de charge et grossesse. Etude de l'évolution de la fréquence cardiaque au cours de la grossesse lors d'un port de charge modéré standardisé.

The object of this study was to look at, on the one hand, the demands made on the pregnant woman's heart and, on the other hand, the effects on fetal heart rate resulting from moderate exercise with a definite rhythm performed by pregnant women. Ten primiparous pregnant women who had normal pregnancies took part in this study in the third and eighth months of the pregnancies. These women were compared with 20 control women who were not pregnant but whose mean age, height and weight were similar to those in the study before their pregnancies started. The maternal heart rate was monitored continuously and the fetal heart rate was recorded telemetrically when the women were carrying 5 kg in each hand with the arms held upright. We will discuss the results that were obtained in the 5 women who followed the course from the beginning to the end of the pregnancy for the sake of this study. The mean heart rate at rest was considerably higher in the pregnant women than in the controls at rest and standing. The heart rate was much higher during the exercise in the pregnant women than in the controls at rest and standing. The heart rate was much higher during the exercise in the pregnant women than in the controls. These changes in heart rate were essentially the same between the 3rd and the 8th month of the pregnancy. The fetal heart rate did not change significantly during nor after the exercise.(ABSTRACT TRUNCATED AT 250 WORDS)