The extensor digitorum longus is a long, thin muscle on the front and outer side of your lower leg. It starts high on the shin and upper part of the fibula, then runs down toward the ankle, crosses the top of the foot, and splits into tendons that attach to four toes. Its main jobs are to lift your toes up (toe extension) and to pull your foot upward toward your shin (ankle dorsiflexion). It also helps turn the sole of your foot slightly outward (a small amount of eversion), which matters for balance and stable foot placement when you walk, run, jump, and change direction.
Even though it’s not an “ab muscle,” it can indirectly affect your progress toward visible abs because it influences how you move. If this muscle is weak or your ankle mobility is limited, your body often compensates by changing your squat depth, shifting weight into the toes, or altering your running stride. Those compensations can reduce training quality, increase fatigue in other areas, and sometimes contribute to shin discomfort. If it’s overworked, you might notice tightness along the shin or a burning feeling during uphill walking, running, or high-rep leg work.
In training, this muscle is active any time you lift the front of your foot or control foot placement, such as during sprint drills, jumping, walking on inclines, and even slow controlled lowering of the foot after a step. Keeping it healthy usually comes down to smart progression in running volume, good footwear choices, and strengthening the muscles that share the workload around the ankle and foot. When your lower legs and ankles work well, your core training and fat-loss work become more consistent, which helps you get lean enough for abs to show.