I remember Davis Phinney saying something WAY back about sprinting. You should brush the backs of your thighs on the nose of the seat when sprinting. Been doing that for the last 19 years.
Also: don't move yer body up and down, angle yer bike side to side when sprinting. Torso should stay relatively still while the bike, arms, and legs go wild underneath you. Don't watch Zabel...
HTH,
M