A higher incline forces you to lift your knees and thighs higher.
Working out on an elliptical machine is primarily beneficial because of its ability to develop the cardiovascular system and burn a high number of calories. Depending on how you set the incline on the machine, however, you can target particular muscles in your lower body. Although the elliptical machine, like other cardio workouts, won't cause you to lose fat specifically in your legs, if your resistance is high enough, you can build strength and tone.
Working out on the Elliptical
When you're riding an elliptical machine, although your feet never leave contact with the pedals, your hips, knees and ankle joints are constantly moving. Your hip joints are extending, which means your upper legs are driving back behind you. The movement at the hips is handled by your gluteus maximus and hamstrings. Your knees are extending, or straightening, as you pedal, thanks to your quadriceps at the front of your upper thighs. Your ankles are performing plantar flexion against resistance, which means your toes are moving down, toward your heels. This movement at the ankle is handled by your calf muscles.
Impact on Muscles from Incline
If you work out on the elliptical without any additional incline, there is only a slightly degree of hip extension, knee extension and ankle plantar flexion. Your legs stay primarily straight as they slide forward and back on the pedals. The movement mimics cross-country skiing. As you increase the incline on the unit, when your legs slide forward, your thighs lift up higher in front of you, your knees bend to a higher degree and your ankles move into a more dorsiflexed position. Therefore, the movement closely mimics climbing stairs. As you drive your legs backward, your gluteus maximus and hamstrings have to perform a greater degree of hip extension, your quads have to extend the knees more and your calves have to plantar flex your ankles more against resistance.
Myth of Spot Reduction
Although a higher incline will place greater emphasis on your gluteus maximus, hamstrings, quadriceps and calves, working out on the elliptical won't cause you to reduce fat in those areas. According to the American Council on Exercise, reducing fat in specific areas isn't possible. Muscle tissue is completely independent of fat tissue. However, as you burn a higher number of calories with frequent elliptical workouts, you'll lower your overall body fat and see improvements everywhere, including in your legs.
Benefits of a Higher Incline
Because your lower body muscles have to work harder with the incline set to a greater degree, your elliptical workout will be of a higher intensity. As a result, your heart rate will beat significantly faster and you'll burn a higher number of calories during your session, which is ideal if you're looking to lower your body fat percentage. In addition, a 2013 study by the Norwegian University of Science and Technology found that cardio training at a vigorous intensity for four minutes three days per week is enough to be healthy and physically fit.