Originally Posted by mander
My instructor at the velodrome told me the stiff armed, no swaying style of sprinting is for track riding, in order to avoid a pedal strike in the banks.
well...its mainly just a lot more stable, which is very important in track racing. the only way you will strike a pedal on a track bike is if you go down onto the apron in a corner, or are on the banking very very low, and your pedal hits the apron while sprinting road style. stiff armed non swaying style helps you keep your line better, but the swaying road style is just more comfortable and natural, and easier to do on a road bike because of the geometry.
if you have an actual track bike with track geometry, try both styles. if you just have a "street" fixie or a conversion, try the road style, or whatever comes more natural to you.