Skip the sit-ups. Instead, try these toning exercises, which engage the abdominals while providing other muscle-toning benefits as well.

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Standing Forward Push

When performing a standing forward push, or chest press, the abdominal muscles work to keep your upper body from shifting or leaning backwards. There are two-arm and one-arm versions of this move—try both. Use resistance tubing at home or a cable/pulley at the gym.

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With the one-arm version, rotate your torso toward the resistance tube as you bring the arm back, and then rotate it away, toward the front leg, as you push the arm forward.  The lower body, core and upper body all work together in this exercise. You can increase the challenge by adding a lunge as the arm comes back and pressing up to standing as the arm pushes forward.

Side and Forward Lunge with Arm Raise

Your abdominals are heavily used here in both the lower-body lunge work and in the single-side arm raise.

This exercise, which uses dumbbells, also challenges the lower body, including the gluteus (rear), hamstrings and quads and shoulders.  Side and forward lunges may be done with the trailing leg bent or a straight leg.

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Keep in mind that this is an intermediate exercise. If you have not been doing lunges and single-arm dumbbell exercises on a regular basis, master those separately before attempting this move.

Single Arm In-and-Out Biceps Curl

Your abdominals are challenged by placing a dumbbell only in one hand, forcing the core to work to keep the upper body centered over the base of support, along with the fact that the weight is moving from side to side, constantly keeping that challenge alive.

Begin with the weight down at your side. Curl the arm across your body, bringing the weight toward the opposite shoulder. Pass back through the starting position and continue to curl the arm toward the outside. Repeat the entire sequence.

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To increase the difficulty, stand on one leg. If you have not been doing standing, single-arm bicep curls, master those before attempting to add the in-and-out motion, and master that motion before progressing to the one-leg version. 

If you are highly deconditioned or have recurrent or chronic back pain, you may need some isolation exercises to prepare you for these types of functional activities. Check with your doctor before trying them, and work with a trainer or other exercise professional to prepare your body and learn proper body positioning.