what is your routine for hiit cardio, im just starting to try it once a week along with 2X a week regular cardio. i just tried one minute sprinting on the treadmill, 1 min walk, then repeat until 20 min is up. this didnt seem like it was near as demanding as running at a consistent pace for 30 minutes, i couldnt really sprint on the treadmill. what have you done that has worked for you, outside or ont he treadmill, what intervals....????