These answers are almost all correct. Every workout should have a goal; actually every run should have a goal, always!. It is early track season for us here on the WC so we might do this as a cruise interval session at tempo pace with 60 to 90 secs recovery. My HS athletes are really not ready for a true max VO2 workout yet. we will do that in starting in late March, and I think a 400 jog is sufficient recovery (which boils down to 2:30 or so) more with the farting around the HS students do.