Seated on the bike with your feet in the pedals, make sure the leg on the lower pedal is comfortably extended or has a slight bend at the knee. Make sure your seat does not tilt forward, which can force you to lean against the handlebars, putting excessive strain on the hands and arms. Hunching over can stress the back and trigger low-back pain. Excessive leaning on the handlebars also minimizes the effectiveness of your workout. Unlike upright bikes, recumbent bikes have more supportive seats, keeping the back straight.
Larger seats are more comfortable.
If it is too large, however, the seat may alter your pedaling motion. If you have to angle your knees outward, you are placing more stress on the joint and not getting the most efficient workout. They put less stress on the knees and help you burn more calories by allowing you to pull up with one leg as you push down with the other. Try it for short intervals for an extra challenge. Your goal should be to get your heart rate up and keep it up throughout the exercise.