The study of limbs kinematics in different conditions and environments

Terrestrial animals are complex, high dimensional, dynamical systems. They have the ability to adapt the coordination of their limbs to move in different environments and at dierent speeds. With the purpose to get in depth into the basic motion mechanisms of animals, in this work the templates and the modular organization of their movements have been studied. This thesis is based on the results of three studies (published in PLoS-One and Esperimental Brain Research). In the text these are referred to as Study I, Study II, and Study III (Chapters 2, 3, 4, accordingly). The rst Chapter 1 introduces a general background necessary for the study and a presentation of the scope of the project. It summarizes available literature on the general organization of the motor systems, focusing on the spinal networks involved in mammalian locomotion and on the limbs motor control. The overall aim and the ow of the thesis are also presented. The specic literature and detailed discussion of the ndings in the context of kinematic and dynamic constraints of limb movement control will be also presented in each chapter separately. The Study I, Chapter 2, presents the study conducted on the modular control of canine limbs kinematics. It explores the framework of kinematic modules for understanding the dimensional complexity of dogs' motor control in locomotion under dierent environmental conditions and speeds. To this end, I studied the kinematic coordination laws of dierent gaits (walk, trot, gallop, and swim) of six dogs (Canis lupus familiaris) and, in particular, the coordination between the segments that constitute each limbs. This study was conducted to see if the kinematics laws found in humans, hold also for dogs, in order to compare the quadrupedal canine locomotion with the human bipedal one. Furthermore, I've also veried that laws was maintained in both hindlimbs and forelimbs, despite their dierent musculoskeletal and functional organization. The Study II, Chapter 3, concerns examination of the inter-limb coupling patterns and understanding how the nervous system coordinates the upper and lower limbs to perform quadrupedal locomotion. We used the crawling paradigm in adult humans to determine which step characteristics are adjusted by the central nervous system (CNS) in order to maintain a 1:1 frequency relationship when treadmill speeds for the upper and lower limbs are manipulated independently and to examine how the relationship between upper and lower limbs changes when the limbs no longer follow a 1:1 frequency ratio. The Study III, Chapter 4, describes examination of the endpoint tory control of rhythmic movement under dierent conditions and environments. We tested human free-hand drawing of ellipses and movements guided by a quasi-elliptic template, in air and in water. The aim of this study was to investigate the potential involvement of kinematic and dynamic factors in the control of endpoint trajectory, and in particular in the relationship between geometry and velocity of the endpoint movement (called Two-Thirds Power Law, 2=3-PL ) Finally, conclusion of the work will be presented, in the contest of general view of kinematic control of limbs motion, both hindlimbs and forelimbs, with future objectives that this kind of research can pursue.