httpv://www.youtube.com/watch?v=r33UMVk1o5s&feature=email

As a scientist in life sciences, I have always tried to highlight the existence of laws. It seems to me that all science should be predictive. Once we are interested in locomotion, the first idea that comes to mind is the following: are there any laws of locomotion that transcend forms, species? Is it possible to predict locomotion of any species to the knowledge of environmental constraints it faces (Legreneur et al., 2012)?

I am not a herpetologist. Over 15 years I have worked on humans, and especially high-level athletes and the elderly. I demonstrated in humans that the trajectory of any point controlled by the central nervous system was still as linear as possible. This point is either the fingertip during a pointing or grasping task, or the body center of mass during locomotion, e.g. during the takeoff phase of a jump. Since most joints move in rotation, and that the controlled point displaces through a linear path, it is necessary to dephase the rotating joints to transform the rotation kinematic energy into linear energy. Finally, for transmiting force from the body to the substrate, for example from the hip to the ground during the jump, the joints move in a proximal-to-distal manner, i.e. the extension of the hip precedes the ones of the knee and the ankle.

To demonstrate that these laws observed in humans were applicable to all terrestrial tetrapods, I am interested in two phylogenetically very distant arboreal jumpers, i.e. a prosimian, Microcebus murinus, and a squamate, Anolis sp. I reproduced with these two species the same experiments that I conducted on humans, i.e. leap up to maximum and submaximal heights. Thus I demonstrate that the coordination observed during take-off in maximal leaping were identical in humans, Microcebus and Anolis (Legreneur et al., 2010; Legreneur et al., 2011; Legreneur et al., 2012). For these three species, the trajectory of the body center of mass was linear along the takeoff. The joints of the hindlimbs rotated always through a proximal-to-distal sequence. This shows that despite different morphologies and despite different organization of the central nervous system, forms of movement are the same. I therefore hypothesized that these locomotor patterns were optimal response to the constraints of terrestrial locomotion in a gravitational field. In humans, these coordinations are not spontaneous, unlike Microcebus or Anolis. It requires training.

I learned from these studies that human locomotion was controlled by inhibitions that were implemented during the evolution. Humans no longer had to escape predators, to catch prey. Consequently, leaping or running are no longer usefull in daily life. These locomotions were inhibited in order to preserve the integrity of the musculoskeletal system of individuals. Thus, only high-level athletes, through training, manage to find an original motor, as it appears spontaneously in anoles. Study of anoles is useful, therefore, to observe locomotion as it was ancestrally. Studying the relationship between morphology and locomotion is also useful to study the mechanism of adaptive radiation and therefore attempt to falsify (in Popper’s sense) previous ideas concerning how adaptive radiation works. Finally, by studying the ontogeny of locomotion, we can understand the extent to which coordination is innate or acquired. In this sense, anoles are an extraordinary model for the researcher.

httpv://www.youtube.com/watch?v=BkNZj08Rfqc&feature=email

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