Running on an incline, whether you are running up hills or on the treadmill, is a high intensity workout with many benefits. Your abdominals are among the many major muscle groups that benefit from incline running, as this exercise builds muscle mass in the abs while also burning fat.
The two major muscle groups in your abdomen that benefit from incline running are your rectus abdominis and your obliques. Your rectus abdominis is the broad, flat muscle that stretches from your pelvis to your lower rib cage, and controls your ability to bend forward. Your obliques are the muscles that run down both sides of your rectus abdominis in a "V" shape, and are responsible for twisting and rotating your torso.
Incline running forces your muscles to work against your body weight as you propel yourself up and forward. This means that your body must work considerably harder than it would on a flat surface, as your muscles are forced to contract more quickly and powerfully. Depending on the height of the incline, your muscles may activate up to two to three times as many fibers as they would on a flat plane. This results in a much more strenuous but rewarding workout for your abs. As you run uphill, your body leans slightly forward as your rectus abdominis contracts to stabilize your torso and keep your back and pelvis straight. Depending on the length of your run, this could mean that your rectus abdominis will remain contracted for an extended period of time, resulting in muscle fatigue and ultimately muscle growth. Additionally, if you pump your arms when you run, the twisting motion of your torso will work out your obliques.
Because your abdominal muscles are usually the primary place your body stores fat, you likely want an exercise that burns this fat and lets the toned muscles show through. Incline running burns a considerable amount of calories, as the incline demands a great deal from your muscles and heart. Once your body has used up the carbohydrates in your system, it will turn to the fat stores, generally located around your midsection, as a source of energy. Incline running increases the level of exertion and cuts into your fat reserves quickly and efficiently. Additionally, muscle requires many times more calories than a similar amount of fat. When you build muscle mass from exercise, you are creating a larger mass with higher caloric requirements, ultimately burning more fat.
Always perform a warm up and cool down period before and after running an incline. Start with some light jogging in place and leg stretches, as this exercise can put a great deal of stress on your leg muscles. Keep your head up as you run rather than staring down at your feet or at the ground. By facing forward you allow greater oxygen intake, which your muscles will then turn into energy.