I've noticed an unusual problem in my 800m races - after the race is over, I'm not tired or breathing hard, but my legs just won't move any faster. My legs are pretty relaxed during the first 300m or so, but they lock up and hurt so bad that it feels like I'm having cramps after a lap and a half.
Any ideas on what to do with this? Is the answer more speedwork or more long aerobic runs?