Sprint Unification Theory
The most common way you'll hear people talk about sprint training is that to improve your speed you need to work hard on your stride length and/or stride frequency. Now, I wouldn't go so far to say that's wrong, but it's a little bit too much of a simplification.
During different phases of the sprint, there's an emphasis towards length or frequency and this is very deliberate. In the acceleration phase, your stride length is deliberately shorter. This is to allow more steps in less time so it can help break inertia and put more force into the ground.
If I deliberately tried to lengthen at my stride during acceleration, it would actually slow me down because I'd reach out in front of the body and that would lead to a heel strike which is basically putting the brakes on with every stride. If I put too much emphasis on stride frequency at top speed, I'm going to tighten up which is going to cost me stride length and cost me flight time.
A more holistic way of looking at sprinting is called the sprint unification theory. I'm not sure who invented it, but I heard it first from Mike Young out of athleticlab.com in California.
It's really quite beautiful. More force and shorter ground contact applied in the correct direction equals more velocity.
More force is all about how efficient your neuromuscular system is. Shorter ground contact time is all about maximising your springiness or reactivity. Better sprinters, no matter whether it's top speed or acceleration, are spending less time on the ground. They're more reactive and they're bouncier. And then, putting that force in the right direction is all about your technique. Having a nice strong knee drive, keeping the foot sprung into dorsiflexion and then striking the ground with the mid-foot under the body.