what about hill intervals? hard to do tabata on a treadmil b ecause by the time its up to speed, its time to switch! 20 seconds might feel like an eternity when youre doing tabata, but slower its not long enough for a treadmill motor to safely go from 4mph to 8mph or whatever. but longer intervals can still be good. ! just dont overdo it. and of course, walking while youre on the phone or watching TV is great.