No, not really. It depends on how much power you put out. It may not matter at all with a stationary bike and/or the shape you're in. Basically, if you were to consider a scale from 1 to 10 on bike power output, with 1 being as slow as you can go, and 10 being some Lance Armstrong types of efforts, a recumbant bike, due to your body position and not the bike's construction, would max you out at maybe a 6. However, if the most you can possibly do yourself is a 3 or a 4, then obviously it doesn't matter. But, that's the biggest difference though. If you put Lance Armstrong on a recumbant, his power output would be significantly lower than his reading on a normal bike. An upright position enables you to pump out more power. Now, whether or not you will, or even can, is a different story. The difference may be similar to putting drag racing slicks on a Ford Escort - you won't be able to utilize the equipment unless you've got the power in the first place.