the thing with crank arm length and gears is that, longer arms <i>should</i> effectively give you more leverage over the gear while a shorter arm gives you a smaller circumference to spin through.

sprinters tend to run shorter cranks, while pursuiters and endurance riders (on the track anyway) run longer crank lengths.

there is little to suggest any of this will affect your performance any more than drinking goat milk prior to a crit.