If you run fast 400m, whats the point to do recover run after it for like 200m.

Question

whats the point of doing it even though your going to run another 400m.

Answer 1

Jeff's right about the lactic acid, another reason, to keep your heart rate up to help build your lungs up so they can perform better longer.

Answer 2

Agree with both of them.  The lactic acid will build up in your legs.  Soaking in a hot bath will also help remove lactic acid if you are sore.

Make sure you do a "cool down" for your muscles.  Also, be sure to stretch before and after you run.  People forget to stretch after, and thats probably more important.

Answer 3

Its to rest your legs, but also to keep them warm. If you ran a 400 then stopped for like a minute your legs will become stiff because of the la tic acid. It will just make the next 400 even harder. Its mainly to increase the quality of the workout.