This was an interesting post I found. In 1979 Coe ran his fastest 400m flat and relay split (45.5). In 1980 he had sciatica, from a pelvic injury. Did this change his action?
He ran his fastest in, what, 1981?
This is what's always interested me: If you watch his races from 1979, his 800 and mile, then watch him from 1980 on, his form seems to have changed. It seems more forced, like he change some element(s) of his training and he looked like he was working harder (OK, he was running faster so maybe he WAS working harder). If you watch his 800 and mile from 1979, the fluidity and bounce and smoothness of stride is amazing. It's like he's still got a full tank! No one was there to push him.
If he could have retained that form and increased his shape, which I don't know whether he really did because it looked like he could have run 3:47 on the day he ran 3:49, I think he could have gone 1:40 or slightly under. That was the year he ran 46.87 in the open 400.