Cant you just take shorter strides until you get to full speed, and then extend to maintain speed? And if you have bigger muscles, wont that negate any increase in weight?
I also, I have been told that running is essentially falling, and then catching yourself. So if you are higher, dont you have more potential energy in the fall? Not sure if that will mean anything.
No, if you shorten your stride you don't fully extend your body during the acceleration phase, you will accelerate quickly but you also hit top speed quickly. As a consequence of shortening the stride is that the rest of the race then depends on your speed endurance because after you hit top speed early you begin to SLOW DOWN, and this happens to everyone even the elites. Whoever slows down the slowest has the greater speed endurance to maintain the momentum of speed from dropping off too quickly. If you were to watch this phenomena on TV it looks like the sprinter is hitting another gear and taking off in the last 20-30 meters of the race, when really what's happening is that he/she is slowing down the least compared to the rest of the competitors.
Aspiring sprinters get into the habit (very quickly i should say) of just moving their limbs fast but not applying necessary power to get ones body moving faster through the track, also cadence is very much dependent on your body mechanics. I must also add that by forcing ones limbs to move faster and generating more cadence you apply your foot longer on the ground and increase ground contact time slowing you down even further, the goal is to be as little as possible on the ground (GROUND IS LAVA) all in the while when you do touch the ground you have to apply the greatest amount of force in that very very very small amount of time.
Your cadence should be the last thing to think about after technique is perfected, conditioning is tapered, and speed endurance is fully actualized. Stride length is ultimately the deciding factor anyway as you move faster due to less time being spent on the ground, while simultaneously generating so much force when the foot touches the ground that elevates the hips to get even higher in the air.
As for the running and catching yourself from falling, it is not quite like that. There is an exercise that sort of has this line of thinking and it is in a way that is used from coaches to find out what lead foot naturally presents itself in an athlete by secretly pushing them off balance from the back. When a novice is first trying to learn how to get off the blocks at a low angle to prolong the acceleration it may feel like you are going to fall on your face, but really this feels like this for only beginners because of course it will feel weird to them and the body hasn't dialed in the mechanical movement to it's nervous system, after a few block starts they will feel fine.
The reasoning for maintaining low angles during the drive phase is to extend ones acceleration, you want to accelerate for the longest time because it means you will hit top speed at the end of the race and very little of the race will be left to speed endurance. Problem is you need to be very strong and powerful to maintain the low angle and the transition from drive phase to fully upright sprinting for the top speed part of the race becomes more critical. If done wrong the accel was for nothing, you will see some guys accelerate very well and then just pop upright and they quickly slow down and everyone will have caught up and passed the individual in a few steps, all that work for nothing.