when d?ing 400 m track sprint on thibedaus running man started out with only three sets with two min rest but man did they wipe me out you have to try this !
As I recall that is his wicked sprint training program.
I commend you. I have never had the balls to try that program. I'm gonna have to put that on the list for next year. Gotta do it. Have you seen Dan John's version?
First you lift something very heavy, Dan recommend Oly lifts but I don't see why sand bags and stones couldn't work too, then you run. It has good reviews so far.
400m is a great distance for sprinting. It takes quite a lot of endurance and will tax your CNS pretty quick if you are SPRINTING.
How about trying a shorter distance and working up to 400m if you so desire?