A stair stepper provides a lower body workout and an aerobic exercise. It engages muscles from your hips to your ankles, including some of the largest muscle groups in your body. These machines often allow you to adjust the resistance of the steps, offering flexibility to strengthen muscles or burn calories according to your needs and goals. Stair steppers provide a low-impact workout, which reduces strain and pressure on your joints as you exercise. Consult with a doctor before beginning a stair stepper workout to ensure it is appropriate for you.
Thigh Muscles
Your thighs stay in constant motion on a stair stepper, ensuring the muscles on the front and back of your thighs get a workout. The quadriceps in the front of your thigh works as you step down and extend your knee. The hamstrings in the back contract as you bend and lift your knee to the top of the motion.
Hip Muscles
The outside of your hips -- the abductor muscles -- add stability to your body as you exercise on the stair stepper, so they are worked to some degree. However, the gluteus muscles across your buttocks work constantly as you step. These muscles help your thighs move forward and backward, so one side is contracting while the other is releasing throughout your step workout. You also target your hip flexors, which are located at the front of your hips and are worked when you raise and lower your legs from the hip.
Lower Leg Muscles
Although you don't usually push off with your toes on a step machine as much as you would when you walk up steps, the gastrocnemius and soleus in your calves still work when you use the machine. At the top of the movement, the calf muscles contract to stabilize your ankle, which is bent slightly forward, and to help your knee bend. At the bottom of the motion, your heel points downward slightly, causing your calf muscles to elongate and stretch while the tibialis anterior muscle along the front of your shin contracts to pull your toes up.
Aerobics
In addition to strengthening and toning the muscles in your legs and hips, a stair stepper provides a fat-burning aerobic workout. According to MayoClinic.com, a 160-pound person can burn 657 calories per hour on a stair stepper. The same person walking for an hour burns about 314 calories. Working your large muscle groups keeps your heart rate up to strengthen your cardiovascular system as well.