Cytrix-On the days when he would run 2 400's, he would rest atleast 5 minutes in between them, and it wasn't unusual for him to rest almost 10 minutes in between them.I tried them with him once and I didn't stop breathing heavy for 5 or 6 minutes afterward, and my legs were sore for about 5 days.His workout was fairly quick.He would run two 400's at moderate speed to warm up,rest about 5 minutes then run his first "real" 400.During his rest period he would walk the track at a moderate pace and then he would do his second 400.This was followed by another walk around the track and some stretching and that was it.I think the reason he rested so much in between was so he could be completely recovered for the next sprint.He also had me timing his sprints, so this may have been a reason as well.