Running is one of the most taxing forms of exercise. While it may seem that the legs do most of the work, running requires the whole body to be fit, toned and strong. More importantly, a tremendous amount of core muscle strength is needed for one to run in top form. Not only does it keep you strong and stable, a strong core also prevents lower back pain and hamstring injuries. Thus, any ab workout for runners must focus on strengthening the muscles of the abdominals, back and pelvis. This is because well-toned abdominal muscles translate to strong pelvic muscles that are necessary to be able to sustain a longer and more powerful run.

The following workouts will develop your core muscle strength so running becomes smoother and more fluid. You can easily incorporate these exercises in your typical running routine.

• Floor Crunch. One of the most basic exercises, the crunch has been tried and tested to strengthen the abdominal muscles. Start by lying on your back with knees bent and feet flat on the floor. Place your fingers by your ears (don't cup your head in your hands). As you curl forward to lift both shoulders off the floor, contract your abs making sure that your chin is kept pointing up and not tucked to your chest. Hold position for two counts before lowering down. Do two sets of 10 to 12 repetitions for this exercise.

• Captain's Chair. This is easily done in the gym on the equipment built particularly for this purpose. If you don't have access to a captain's chair, however, you can still do this challenging ab workout on a regular chair by following these instructions: Sit on the chair with your hands on the sides. Putting your body weight onto your hands, lift your thighs up a few inches off the chair while keeping your knees bent before slowly lowering them back down. Do this for two sets of about 10 to 12 repetitions.

• Plank/Side Plank. One of the more advanced core muscle workouts, the plank/side plank strengthens the muscles of your abdomen and lower back to give your body that much needed stability as you run. Begin in a push-up position. Make sure that you keep your body in a straight line as your forearms hold you steady and your elbows are placed directly below your shoulders. Your abdominals must be pulled in. Hold this position for 30 seconds. For the side plank, shift to your side, keeping one elbow directly under your shoulder as you do so. Both feet should be on the floor with your top foot in front. Slowly raise your hips until your body is in a straight line. Hold this position for 30 seconds before doing it to the other side. As your core muscle strength improves, you should be able to hold the plank/side plank positions for a couple of minutes.

• Standing Broad Jumps (Double Leg Hops). An important exercise that should form part of a runner's routine, broad jumps stabilize the trunk by forcing your hips and abs to work together. Begin in a standing position then jump as far as you can using your arms to pull yourself up. As soon as you land, jump again three times without stopping. Do these in three sets, resting only for two minutes in between.

• Swiss Hip Extension. This exercise stabilizes the body by making the hip flexors and glutes work with the abs and back. Sit upright on a stability ball. Walk your legs forward, letting the ball travel up your spine to your shoulder blades. Keeping your arms extended out to the sides, raise your hips up until your torso is parallel to the floor. Continue by lifting one knee at about a 45 degree angle and lowering it down again. Finally, lower your hips toward the floor. Repeat motion on the other side for one set. Perform these for three sets of five to seven repetitions. Rest for two minutes between sets.