I think the idea that reducing ground contact time makes you run faster is putting the cart before the horse. Ground contact time, for a specific individual, is controlled by how fast he/she is moving over the ground. Unless the sprinter’s mechanics are altered, the foot strikes the ground in the same relative position (under the body) and leaves the ground at toe off in approximatel the same position as before. In other words, an elite sprinter who improves his max speed doesn’t contact the ground farther behind his center of gravity, and doesn’t toe off earlier in his stride. The ground contact time is shorter simply because he is going faster over the ground, the legs are traveling through space faster, and the foot spends less time on the ground.
The first assumption is the correct one, IMHO, that to go faster you need to apply more force during the alloted ground contact time. To go faster, even more force has to be applied during what is now a shorter contact time.
Improving your ability to generate force, and steepening your personal force/time curve (be able to generate more force and apply it at a higher rate) is what makes you run faster. The ground contact time, while it limits the time alloted to generate force, is an artifact and product of speed, not the other way around, IMHO.
I agree, in general, with you. The Weyand study was descriptive, not prescriptive. It is like someone telling me that the fastest guys run 100m under 10s, while this is true, it does not tell me in any way how to do the same.
Some people used to think that faster guys had much faster stride frequency; Weyand showed that in fact there is little difference in that respect, the key factors being force produced on the ground and time spent on the ground. This is good, but so what? How can I accomplish these things? He did not say, nor should he, because he is a scientist, and they understand the limits of their research; however, lay people rarely do, and so tend to extend scientific results unwarrantedly. Unfortunately, some mystical people make an entire training system based on these studies, and all of a sudden getting as strong as possible is seen as the crux for greater speed.
In my opinion, fast running is mainly a neurological skill, something that has to be developed by many hours of practice. Some people are more gifted than others, so they learn what muscles to activate more efficiently and quickly than others. But we all need practice. And what is the best practice? This cannot be answered scientifically, the variables are too numerous and inter-related. We can only go on experience. Try and model what the most successful people have done, and make it fit your situation. Nothing more to it. Describing to me how great guys run fast does not, and will never, help me to run faster because the “how” is too individualistic.