This is what I do for cardio 1-2x a week and how I get my workouts in without a daycare or babysitter around. workout: 5 minute warmup (easy jog) 20 seconds all out sprint (on a hill is even better if you can) 2 min 30 second slow recovery jog repeat the sprint/recovery jog 4 times 5-10 minute cooldown should take you 21-26 minutes total.