what the other 2 posters have said, and bike fit. you mentioned body position in regards to its importance in swimming and that idea applies to the bike too and how you fit on it. how well you end up sprinting, in races and in training (which impacts the races!) depends upon bike fit and your most efficient/powerful/balanced position (assuming your training for road racing/fast riding).
just as in swimming when you practice strokes w/ good form and proper hand/arm/body/leg positioning/movement to train your muscles to work most efficiently in order to achieve speed/power you need your best position on the bike to get those muscles in the best position and train them accordingly.