Quads and not hamstrings??

Hey all. I am just starting to train back for the 400 coming down from the 800. I am starting short, ie. today I did 5x20m. Usually, or at least last year when I was doing intensive 400m training, my hamstrings would feel the burn, and my quads would only be tired, but never sore. Now, my quads are sore and not my hams. I read that Desai knew he had run well when his ham’s were feelin’ it, and I know this is true too. Anyone have thoughts as to why this is? are my hips dropping? I appreciate it all!
Mike

I think it is natural to feel like your quads are working from 0-20m , you are not yet in the sprint position and are probably still “pushing”.