Ever do anchored sit-ups or leg raises? The problem is that if the femur is moving much, you are really working your hip flexors. Anchoring your legs during sit-ups, placing your legs further out, or even doing leg raise types of abdominal exercises increases hip flexor activity and may cause disc compression. It also increases risk for low back pain aggravation.

So what’s a better way to work your abs? Abdominal curl-ups, especially if done on an exercise ball, can more effectively activate the abdominal muscles. Abdominal curl-ups place the majority of the resistive stress in the rectus abdominis. Rollouts also are effective for engaging the trunk musculature without hip flexion.

Additionally, consider this: Almost every lift you do, from squats to standing alternating dumbbell curls, activate your abdominals in one way or the other. I’m not a subscriber to the theory that you shouldn’t work your abdominals, but if you are exercising and doing daily resistance training, you are indirectly working them all the time! What this leads to is that if you can’t see your ab muscles, you are probably packing too much body fat and should adjust your diet.

Summary: Choose ab exercises where the femur is largely anchored and not flexed in, and reduce calories to reduce body fat.