Kinematics and Dynamics of Burst Transitions

Abstract

ABSTRACT. Subjects (N = 14) were instructed to walk at comfortable walking speed and to start sprinting on an external (visual) stimulus. This is a burst transition. To accelerate maximally, different strategies can be used. The choice for a strategy was hypothesized to be (a) dependent of the body's dynamical status, which is in its turn dependent on the signal timing within the gait cycle; and (b) influenced by the performance and efficacy of the different strategies. Three-dimensional kinematics and ground reaction forces were used to discriminate between strategies and to calculate work (W_total). Distance laser data yielded performance measures and the work related to the forward acceleration (W_objective). Efficacy was calculated as the ratio of W_objective to W_total. Subjects mainly used 2 strategies among others depending on the timing of the stimulus: (a) subjects placed their body center of mass (BCOM) in front of their center of pressure (COP) by tilting the trunk forward and flexing the knee, resulting in a sudden forward acceleration but a relatively fair efficacy; (b) subjects placed their COP behind their BCOM by placing the foot of the swing leg backward. This led to a high performance with high efficacy and was therefore the most ecologically relevant.

Keywords:

• biomechanics
• biped
• gait transition
• locomotion

ACKNOWLEDGMENTS

V. Segers and I. Van Caekenberghe contributed equally to this manuscript. The authors acknowledge D. Spiessens for technical support.

FUNDING

This research was supported by Research Foundation-Flanders (F6/15DP G.0183.09 and FWO08/ASP/152) and the European Community's Seventh Framework Programme FP7/2007–2013—Future Emerging Technologies, Embodied Intelligence, under grant agreement no. 231688.