Here we show theoretically that swimming animals and athletes gain an advantage in force and
speed by spreading their fingers and toes optimally. The spacing between fingers must betwice
the thickness of the boundary layer around one finger. This theoretical prediction is confirmed by
computational fluid dynamics simulations of flow across two and four cylinders of diameter D.
The optimal spacing is in the range 0.2D – 0.4D, and decreases slightly as the Reynolds number
(Re) increases from 20 to 100. The total force exerted by optimally spacing two cylinders
exceeds by 53 percent the total force of two cylinders with no spacing when Re = 20. These
design features hold for both time-dependent and steady-state flows.