Cognitive style in attainment of an upside-down posture in water with and without vision.

It is well known that adopting a posture required by the central nervous system takes into account a frame of reference. This frame of reference is built on sensory information and, more particularly, on vision, which is often considered to be the main input. The contribution of vision varies by participant and defines their cognitive style. This study investigates the contribution of visual information and cognitive style to postural strategy and, more precisely, to the construction of an upside-down posture in an underwater condition. Eight synchronized swimmers performed the Rod-and-Frame Test (RFT) to assess their cognitive style and practiced upside-down posture in water to measure their body inclination. The Rod-and-Frame Test scores did not distinguish the participants, as the results of the test showed that most of them were visual-field independent. However, in a closed-eyes condition, participants achieved a more precise vertical position than when using translucent goggles.

Interpersonal distance modeling during fighting activities.

The aim of this article is to elaborate a general framework for modeling dual opposition activities, or more generally, dual interaction. The main hypothesis is that opposition behavior can be measured directly from a global variable and that the relative distance between the two subjects can be this parameter. Moreover, this parameter should be considered as multidimensional parameter depending not only on the dynamics of the subjects but also on the "internal" parameters of the subjects, such as sociological and/or emotional states. Standard and simple mechanical formalization will be used to model this multifactorial distance. To illustrate such a general modeling methodology, this model was compared with actual data from an opposition activity like Japanese fencing (kendo). This model captures not only coupled coordination, but more generally interaction in two-subject activities.

Path integration: is there a difference between athletes and non-athletes?

The ability to estimate distance walked when blindfolded is associated with the vestibular, proprioceptive and (loco-)motor systems. In this study, we examined subjects' ability to walk when blindfolded to a previously seen target. We examined whether there is a difference of performance in path integration between athletes and non-athletes. Two groups of healthy volunteers took part in this experiment: 21 athletes and 20 non-athletes. Subjects were asked to walk at three different velocities (slow, normal, fast) to a target (10 m in front of them) that they had seen before being blindfolded. Increase in velocity was associated with a decrease in the distance walked for both groups. Both groups were accurate at normal velocities. Athletes were also accurate at fast velocities whereas non-athletes undershot the target. In both groups, accuracy considerably decreased at slow velocities. It seems that our perceptual system can adapt to different velocities (normal, fast) but is most strongly disrupted at low velocity. When attempting to modify walking velocity, step length is also modified, playing a determining role in the estimation of distance.

Timing and distance characteristics of interpersonal coordination during locomotion.

Most studies about human locomotion only tend to consider single subjects walking alone in a stationary environment. Nevertheless, human subjects have often to plan and generate their locomotor trajectories according to one another's displacements. Therefore, in the present study we address the question of the interpersonal coordination when pairs of subjects walk simultaneously. Six pairs of subjects walking face to face, backwards and forwards on a 8 m x 2 m track were involved in our experiment. Within each pair, the leader (L) was required to break the initial interpersonal distance whereas the follower (F) had to maintain this distance constant (1, 2 or 3 m). We measured their position and analyzed their travelled distance, the time course of their linear displacement, and the kinematics parameters of their steps. Our results show that F travels smaller distances than L and that even if they are highly correlated, some temporal delays exist between displacements of L and F with greater values when the interpersonal distance increases (from 1 to 3 m). These results are discussed in terms of high level imitation, i.e. bidirectional interactions with mutual influences of each subject on one another.