Strengthen and tone your midsection with this simple and effective move that doesn't require endless repetition. Make sure your form is precise and that you use complete control to get the maximum benefit.

1 Lie face up on the floor (or exercise mat), both legs straight in front you. Inhale and, with both hands, hug your left knee, bringing your chest and face as close to your knee as possible. On an exhalation -- keeping your chest and head up -- raise your right leg off the floor a few inches. Pause and focus on strongly contracting your abdominals to maintain the upper-body curl.

2 Without allowing your upper body to drop down, straighten your left leg up toward the ceiling. Draw your navel in toward the spine and try to bring your chest closer to your left thigh; hold this position for two to three breaths. Release, lowering your legs and chest to the floor. Rest a few seconds and repeat using the other leg.

This article originally appeared in the Los Angeles Times in the "Good Form" feature of the Health Section. "Good Form" is updated with a new Karen Voight article each Monday.