For complete abdominal strengthening, include exercises to train your transverses abdominis. When strong, this muscle keeps your midsection trim and flat, improving your posture and making your silhouette slimmer. You can engage the transverses abdominis every time you start to do a traditional ab crunch by performing a split-second contraction before fully flexing other abdominal muscles. This will help get the most out of all your abdominal work.
1 Lie on a mat or padded surface with both knees bent directly above your hips and with your calves parallel to the floor and ankles together. Rest your arms on the floor at 45 degrees to your body with palms facing down. Inhale, then exhale and press your navel toward your spine.
2 Stabilize your back against the mat as you lower one leg toward the floor. Switch legs and focus on keeping your abdominal muscles contracted as you continue alternating legs for 15 to 20 seconds. Be sure to keep your head and arms resting on the floor and continue to breathe throughout the exercise without letting your back arch away from the mat.