To achieve an hourglass shape, you can tone your obliques, which are the abdominal muscles that run along the sides of your waist, with various exercises. Think of your obliques as the right and left sides of your body's natural corset. If you tighten this corset and shrink your waist, it'll accentuate the curve of your hips.
Rely on Body Weight
Perform isolation exercises, such as oblique crunches or side crunches, using only your body weight to target your obliques. For example, begin an oblique crunch by lying supine on the floor with your knees bent and your feet planted on the floor. You can also rest your calves on a bench. Place your right hand behind your right ear, and extend your left arm to the left side with your palm facing up. Exhale and draw your right elbow to your left thigh, holding the peak position for a second. Inhale and return to starting position. Perform three sets of 30 reps, and then repeat the exercise on your left side. The combination of high volume and low overload enables you to achieve greater definition of your obliques without adding bulk.
Carve Curves with Bands
You can use elastic bands as a form of resistance for trunk rotations, which condition your obliques. For example, sit on the floor with your legs shoulder-width apart and extended. Loop the middle of the band around your feet, and hold the ends of the bands with your arms extended in front of you. Slowly twist your trunk to the right, keeping your arms aligned with your chest and drawing the band to the right. Avoid rotating your trunk more than 45 degrees. An extreme amount of rotation may put too much stress on your spine and doesn’t increase the effectiveness of the exercise. Return to the center, and then repeat the rotation to the left side, which completes one rep. Perform 12 to 15 reps for two or three sets. You can also perform a trunk rotation on a cable machine from a standing or kneeling position.
Challenge with a Chop
The woodchop exercise, in which you pull a cable in a diagonal trajectory across your body, works the front abdominal wall and your obliques. You can draw the cable from a low point to a high point or the reverse. The movement resembles the sheathing or unsheathing of a sword. Begin by securing a rope handle to the low pulley of a cable machine. Stand sideways about three feet away from the machine with your right side closer to the weight stack. Place your feet shoulder-width apart with your knees slightly bent, and hold the handle with both hands as if you’re holding a bat. Exhale and draw the handle up and across your body in sweeping motion until your hands are above your left shoulder. Hold the top position for a count, and then inhale and return to starting position. Aim to complete 12 to 15 reps, and then repeat the exercise on the other side.
Balance and Twist on a Ball
A trunk rotation on an exercise ball with a dumbbell is an advanced exercise that’ll work all of your core muscles -- obliques, front abdominals, lower back and spinal muscles. Begin by lying supine on an exercise ball with your neck, shoulders and upper back rest on the ball. Bend your knees and plant your feet on the floor, lifting your hips so that your body forms a straight line. Hold a dumbbell with both hands, extending your arms directly over your chest. Rotate your upper body to the right until your arms are parallel to the floor, and allow your head to track the movement of your arms. Hold the peak position for a second, and then perform the rotation to your left side. Perform two or three sets of 12 to 15 reps. Increase the intensity of the exercise yet another notch by using a heavier dumbbell.
Monitor Your Spine
Avoid exercises involving torso twists if you have issues with your back or cervical vertebrae. If you have a healthy spine, you can perform trunk rotations, but don’t force or exaggerate the degree of rotation. Use fluid controlled movement during rotations, as sudden or jerky movements can put too much pressure on your vertebrae. Perform five to 10 minutes of light aerobic exercise as a warm-up for abdominal exercises.