My favorite is to use an elliptical machine, warm up a little then crank it to maximum resistance and just go as hard as I can until I'm done. I can induce a "r

My favorite is to use an elliptical machine, warm up a little then crank it to maximum resistance and just go as hard as I can until I'm done. I can induce a "runner's high" within a few minutes that feels amazing, and I prefer it to treadmill/cycle for the whole-body workout (you can really utilize arms/shoulders/back/core on the elliptical) I'm usually done within 10 minutes, and if I've been out of practice I can certainly feel it the next day.