The start in speed skating: from running to gliding.

The purpose of this study was to describe the push-off kinematics in speed skating using three-dimensional coordinates of elite male sprinters during the first part of a speed skating sprint. The velocity of the mass center of the skater's body VC, is decomposed into an "extension" velocity component VE, which is associated with the shortening and lengthening of the leg segment and a "rotational" velocity component Vr, which is the result of the rotation of the leg segment about the toe of the skate. It can be concluded that the mechanics of the first strokes of a sprint differ considerably from the mechanics of strokes later on. The first push-offs take place against fixed location on the ice. In these "running-like" push-offs the contribution of Vr in the forward direction is larger than the extension component Ve. Later on, the strokes are characterized by a gliding push-off in which Ve increases. In these gliding push-offs no direct relation exists between forward velocity of the skater and the extension in the joints. This allows skaters to obtain much higher velocities than can be obtained during running.