I don’t have any data on this…its primarily from what I’ve read on other sites and stuff. I know when a athlete goes upright doesn’t mean acceleration is stopping, but there is usaully a correlation.Clearly we just disagree and its kind of pointless to just say the same things about things we disagree on.
And just out of curiosity, why do you favor tall posture quickly?
To be clear, I don’t teach athletes to stand up right away. I just don’t bother making kids stay artificially low when their sprint mechanics are not very good, and they aren’t strong enough to do so anyways.
I favor the upright position for a number of reasons. One is that I predominantly work with high school athletes. As Roswell pointed out, you have to be upright in the hurdles in under 15m. In relays you have to be upright and taking the handoff in about 20m. And in the longer sprints, staying low isn’t really relevant anyways. So what I come to is the idea that low acceleration mechanics are only important (at my athletes’ level) for 100m specialists with relatively high performance. Everyone else needs to learn how to run first.