Dynamics of gait transitions

Although many studies deal with transitions between gaits and several alternative hypotheses on ultimate and proximate causes are provided, surprisingly little information is available on what actually happens kinematically and dynamically when changing from one gait to the other. Nevertheless, this kind of basic information seems indispensible for further insights in the control of transition and to speculate on the nature of proximate triggers. As gait transitions typically occur during whole body accelerations, they are studied overground. We measured 3D kinematics, ground reaction forces and (in a limited set of experiments) muscle activation patterns in humans throughout transition from walking to running (and vice versa; typically 3 steps before and 3 steps after the transition). Three experimental conditions are used: accelerating constantly (controlled rate), during spontaneous accelerations and when performing a burst transition (fleeing). Next to the descriptive kinematics and forces, whole body dynamics and joint dynamics are calculated to characterize the transitions. Comparisons with transitions towards the uncommon bipedal galloping gait in humans and with trot-canter transitions in quadrupeds are made. In a parallel study, a powered foot-ankle exoskeleton is used to explore to potential role of lower limb muscles in triggering the walk to run transition in humans. In the context of the development of legged robots, able to switch autonomously between gaits according the circumstance (e.g. towards more dynamic gaits in order to exploit actuator compliance), insights gained from nature may be very useful