There are lots of core exercises out there. Doing any of them is better than doing none of them. But some are definitely better for runners than others.
A strong core--that is, strong abdominal and low-back muscles--enhances running performance and may reduce injury risk. The best core exercises for runners are those that mimic the specific ways the core muscles are required to work during running. Here are three moves that do just that.
Supine March
Why it's good for runners: Core stability begins with the transverse abdominis, a deep abdominal muscle that needs to hold the right amount of tension to prevent excessive movement of the pelvis and lumbar spine during running. The greatest challenge this muscle faces in running is maintaining appropriate tension while the legs move freely and alternately. The Supine March is a great exercise for runners because it administers that very challenge in a controlled way.
How to do it: Lie face up in the floor with both knees sharply bent and your feet flat on the floor. Press your low back into the floor. While concentrating on keeping your low back pressed into the floor, lift your left leg until your left foot comes even with your right knee. Now lower the foot back to the floor. Repeat with the right leg. Continue until you begin to feel an uncomfortable burn in your tummy, up to 20 reps per leg.
Standing Trunk Rotation with Cable
Why it's good for runners: One of the important jobs of the core muscles during running is to control rotational forces. Among the biggest energy wasters in running is excessive rotation of the hips, pelvis, and/or spine. The Standing Rotation with Cable isolates and intensifies this particular challenge.
How to do it: Stand with your left side facing a cable pulley station with a handle attached at shoulder height. Grasp the handle with both hands and both arms fully extended. Begin with your torso rotated toward the handle and tension in the cable (i.e. the weight stack is slightly elevated from the resting position). Rotate your torso to the right while keeping your arms fully extended and the handle in line with the center of your chest. Keep your eyes focused on the handle as you rotate and your hips locked forward. Return to the start position without allowing the weight stack to come to rest. Complete 12 repetitions, then reverse your position and repeat the exercise.
Suitcase Deadlift
Why it's good for runners: Running is all about moving against gravity in an upright position. Most core exercises don't mimic this fundamental element of running. The Suitcase Deadlift does. In particular, it trains the oblique muscles on the sides of the torso to do what they are asked to do during running, which is to keep the torso vertically in line with the legs against resistance. The low back muscles are also challenged in a running-specific way in this exercise.
How to do it: Stand with your arms hanging at your sides and a dumbbell in one hand. Push your hips back, bend the knees, and reach the dumbbell down as close to the floor as you can without rounding your lower back. Now stand up again. Don't allow your torso to tilt to either side while performing this movement. Complete 10 repetitions, rest for 30 seconds, then repeat the exercise while holding the dumbbell in the opposite hand.