  The skill to swim fast results from the interplay between generating high
thrust while minimizing drag. In front crawl, swimmers achieve this goal by
adapting their inter-arm coordination according to the race pace. A transition
has been observed from a catch-up pattern of coordination (i.e. lag time
between the propulsion of the two arms) to a superposition pattern of
coordination as the velocity increases. Expert swimmers choose a catch-up
coordination pattern at low velocities with a constant relative lag time of
glide during the cycle and switch to a maximum propulsion force strategy at
higher velocities. This transition is explained using a burst-and-coast model.
At low velocities, the choice of coordination can be understood through two
parameters: the time of propulsion and the gliding effectiveness. These
parameters can characterize a swimmer and help to optimize their technique.
