The choice of Stationary Bike over Elliptical Machine may be a controversial one, but I'm sticking by it. I've had knee problems off and on over the last few years, and the stationary bike is much easier on my knees than the elliptical machine. Many a time I have felt a twinge in my knee as I make a misstep on the elliptical, but never while cycling. [caption id="" align="aligncenter" width="700"] Source: www.brookstone.com[/caption] That's not to say cycling is all peaches and cream. The feeling of a numb bottom is HIGHLY unpleasant, and the poor "gentlemen" in my pants often protest as I cycle. I still prefer the stationary bike. You can get a much better workout just by pedaling in the standing position, and you'll give your legs a much harder time than you could with an elliptical machine. There's also a lot less pressure placed on your knees, and you can adjust the seat to the perfect height for a comfortable cycling workout. Doing your HIIT training on the bike is as easy as pedaling at top speed or standing up for your high intensity interval!