Fig. 10. Transect of the vortex wake of a synchronous kick (A) and the corresponding velocity profile perpendicular to the transect (B). Positive velocity is forward, showing an augmented forward velocity between the vortex rings. There is no backward-directed central jet produced at the end of the kick as the feet come together. If anything, there may be an interaction between the vortex rings produced during the kick, increasing the forward velocity between the vortex rings. The forward velocity between the rings may also be partly due to the drag wake of the body.