Training improves the adaptation to changing visual conditions in maintaining human posture control in a test of sinusoidal oscillation of the support.

Balance control relies on somesthetic, visual and vestibular afferences, their central processing, and adequate motor responses. We studied the consequences on postural control of the suppression of visual afferences by eye closure, during a dynamic posturographic test in six sportsmen and 14 non-sportsmen. Suppression of visual afferences during the test led to a prolongation of the pattern initially recorded with eyes open, followed by a transitory adaptive pattern, then a typical eyes closed pattern. Repetition of the test showed a progressively longer persistence of the eyes open pattern and disappearance of the adaptive one. This evolution was significantly faster in sportsmen. This progressively longer duration of the eyes open pattern may be explained by the intervention of short term memory. Our data further indicate that training improves adaptive posture control.

Dizziness in discus throwers is related to motion sickness generated while spinning.

While both discus and hammer throwing involve rotating movements resulting in the throw of an object, discus throwers sometimes report dizziness, a condition never experienced by hammer throwers. We investigated whether this susceptibility was related to the sensitivity of the thrower or to the type of throwing achieved. For the latter, we compared the determining features of gesture, gaze stabilization and projectile trajectory in both sports. A total of 22 high-level sportsmen in these 2 disciplines, half of them practising both sports, were interviewed. Slow motion video recordings of discus and hammer throwing were examined to determine the visual referential, head movements and plantar surface support area involved at each stage of the motions. Discomfort was reported by 59% of the sportsmen while throwing discus, but by none while throwing hammer. Because several individuals practised both sports, these results exclude the hypothesis of individual susceptibility to dizziness. Video analysis evidenced that during hammer throwing, visual bearings can be used more easily than during discus throwing. Moreover, there is a loss of plantar afferents and generation of head movements liable to induce motion sickness, such as Coriolis acceleration. In conclusion, although hammer and discus-throwing present numerous similarities, we demonstrate here that crucial differences in the specific execution of each sport are responsible for the dizziness experienced by discus throwers.

Why do idiopathic scoliosis patients participate more in gymnastics?

The influence of physical and sporting activities (PSA) on idiopathic scoliosis (IS) is still obscure. The aim of this study was to investigate whether such an influence exists and if so, to determine its characteristics. Two hundred and one teenagers with IS and a control group of 192 adolescents completed an epidemiological questionnaire. Those practising gymnastics were more numerous in the IS group than in the control group. Moreover, the practice of gymnastics was chosen before IS was diagnosed. As gymnastic activities are considered neither as a therapy nor as a precursor of IS, the distribution observed could be linked to a common factor that both increases the likelihood of IS and favors the practice of gymnastics. Joint laxity (JL) may be such a common factor, and was therefore tested (wrist and middle finger) on 42 girls with IS and 21 girls of a control group. IS patients, practising gymnastics or not, showed a higher JL than the control group practising gymnastics or not. Furthermore, the groups practising gymnastic activities did not show higher JL levels than the other groups. Children with a high JL could be drawn toward gymnastics because of their ability to adapt to the constraints of this sport. Girls with a high JL may therefore be prone to developing IS. The fact that most teenagers with IS practise gymnastics could be related to a higher JL.

Selective pup retrieving by mother rats: sex and early development characteristics as discrimination factors.

Discrimination between own-litter pups by mother rats was studied over 14 litters, in a standardized situation eliciting maternal pup-retrieving activity. Results showed some consistency in the order in which pups of a litter were retrieved by the mother in the 4-day and 9-day tests and that this order was related to certain characteristics of the pups: 1) on Day 4 and 9, the best-developed pups of the litter (in terms of body weight and neuromotor behaviors) were first retrieved; 2) on Day 9, sex of pups became an additional discrimination factor, as males were retrieved before their female littermates. Variables included in these global discrimination factors and possible consequences of such differential mother-pups interactions are discussed.

Maternal behavior variations and adaptations, and pup development within litters of various sizes in Wistar rat.

Variations of two maternal behavior components (time spent with litter and rapidity of pup retrieving) as well as certain physical and developmental characteristics of pups (weight, relative weight gain, and neuromotor maturation) in rats were simultaneously studied in 29 various-sized litters in which interindividual variations were not experimentally amplified. Results showed mothers' behavioral adaptations to litters' characteristics (size and weight). Time spent with young was linked to litter size, whereas rapidity of pup retrieving was related to the pups' physical characteristic. Beyond these adaptive variabilities, residual variations subsisted between mothers. These variations were determinant for differences in pup development for only one component: the time that mothers spent with their litters, while pup retrieving component variations did not have any effect.

Behavioral profiles of adult rats in a difficult food supply social situation, related to certain early behavioral features.

Behavioral profiles of male rats were defined in nine intralitter groups of six individuals at various stages of their development: (a) at pup stage in individual situations (uncomfortable positions) and social situations (removal away from the mother), and (b) at adult stage in a difficult food supply social situation (complete immersion of the food access way). The male population was split into two sets, both at pup stage (the most and the least swift and efficient of each group to overcome uncomfortable situations), and at adult stage (carriers and noncarriers of food in each group tested). Our results showed an important relation between these pup and adult behavioral profiles: the swiftest and most efficient individuals of a group at pup stage adopted more often a food carrier behavioral profile at adult stage. Assumptions about the predictive value of some behavioral features of a young rat in regard to its adult behavioral profile are discussed.