A stationary bike offers the ideal low-impact exercise. But many times, users don’t adjust the bike to fit correctly. When adjusting seat height, make sure to have the ball of your foot on the pedal and only a very slight (5 to 10 degree) bend in your knee. If you sit too low (a common mistake) your knees flex too much as you pedal. This puts too much pressure on your knees–and because your legs won’t go through a full range of motion, you’ll burn fewer calories as a result.