Should a swimmer’s arms serve as paddles or propellers? That
question, abstruse as it might seem, underlies a long-running
controversy in swimming about the best, most efficient technique
for the freestyle and the backstroke. It also prompted a new
study from a group of scientists at Johns Hopkins University
that, in seemingly answering the question, is likely to provoke
even more debate. Gretchen Reynolds on the science of fitness.
Gretchen Reynolds on the science of fitness. The physics of
swimming are simple enough. To move through the water, you must
generate thrust. To do so, you can use dragging or lifting
forces. Drag is created by, unsurprisingly, dragging back
against the water and, in the process, pushing an object, like
the swimmer’s body, forward. Lift, on the other hand, is created
mainly by the flow of fluid around an object moving at an angle
through the water. The fluid flows faster around the more curved
side of the object, lifting and thrusting it forward. Ship
propellers work on this princi