forgive me if i don't have the studies, but i thought( so i can be corrected) that sprints hit the anerobic energy system hard and also help the aerobic, i remember in basketball we did a lot of wind sprints and suicides, but long slow distance doesn't really touch the anerobic system. also the def. i hear a lot for aerobic, is if you can have a comfortable conversation you are in that zone...never saw guys chatting while sparring or able to chat,just my exp.