Originally Posted by
Swill
Doing on outdoors, on a track, or even a little bit of an incline if you're a badass, is definitely more taxing and you get more from it than on a treadmill. The acceleration part that is taken out in treadmill sprints as you 'join in' at a fixed pace, and that is the explosive element that you get a lot of benefit from, physically and hormonally.
I do them on a treadmill at the moment purely down to a niggling lower back issue but soon will be back to outdoors... I do get the benefits from treadmill but its not near as good as in the great wide open.