One of the common denominators of those who were really fast to 10 in the past (and to some extent even now) is that they stood up much quicker. Check out FloJo, Cason, Ben and you’ll notice they look like they’re almost upright at 15m. Compare that to today’s runners who display much better 10m splits in the latter half of the race but come up much slower.
So Mike, does this all come back to preserving energy and / or the hamstrings for later in the race?