A recumbent bike is a cardiovascular machine that gives you a similar workout to a regular exercise bike. The difference is with the way the bike is set up. On a recumbent bike, there is a bucket seat with a backrest. The pedals are out in front of you, so when you operate the machine, you are in a horizontal position. This can take pressure off your lower back and prevent you from slouching. Even though the bike is a piece of aerobic equipment, there are multiple muscles that you will work when you use one.
The gluteus muscles, or glutes, are the major muscles that compose your butt. These muscles get called into play every time your thigh goes from a position close to your body to a straightened position. This motion is known as extension.Your leg extends and your glutes engage every time you push down on a pedal.
The quadriceps are the large muscles on the front of the thighs. They function as knee flexors. They get worked on the recumbent bike to assist the glutes when you push the bike pedals, and also to help draw the leg back up again at the top of the pedaling motion. The smaller muscles on the inner sides of the quad--the adductors--also get recruited with this motion.
The hamstrings are on the back of the upper thighs. They are the opposing muscle group of the quads and their main function is to flex the knee. You see this action when your lower leg goes from a straight position to a bent position while pedaling. They activate along with the quads to draw the foot back to the top of the pedaling cycle
The calves are on the lower back part of the legs, below the knees. They are comprised of the gastrocnemius, which is the upper part, and the soleus, which is the lower part. Every time your foot goes around and you point your toes downward, you are working your calf muscles. This is called plantar flexion.
The tibialis anterior muscles oppose the calves. They run down the front of the shins and they get worked when your toes point back towards your body during pedaling.
The abdominal muscles, or abs, are stabilizers that get called into play when you are pedaling. They help balance your upper body and they also promote drive strength when you are cranking.