I think you are making the assumption that if someone has an upright posture they have stopped accelerating,they are still accelerating just not as well as you can could do. There is plenty of data around just most is not available easily online. Star61 summed up this entire argument perfectly, I’d suggest re-reading his post.
I have been reading this thread very thoroughly…I just disagree with the points you guys are making. I was not suggesting that acceleration stopped when one becomes upright, but there is a bit of a correlation between when one becomes upright towards when they stop accelerating. I think the points said have validity, I’m just trying to suggest that the range of when acceleration stops is a bit wider than has been suggested, and I think the better the power levels and mechanics a athlete has the longer acceleration will last timewise.