The Airdyne KILLED me. When I first bought the thing back in late October, I tried out some short bursts of high-intensity - maybe 5 seconds or so. It seemed too easy, and I was worried it wouldn't produce the same effect as the rower or the prowler. Holy shit was I wrong. Twenty second intervals on that thing are tougher than rower, prowler, and hill sprints, at least in my experience. I spent a FULL HOUR trying not to puke, and I didn't even do 4 full intervals. The aim is eventually 8, and then adding a second day per week. For now, I'll do one day, and try to add intervals as becomes possible. Hopefully 4 full intervals is possible next time. Lord.