Abdominal muscles are connected throughout the entire midsection of the body, so the distinction between lower or upper abs means little in purely physical terms. Still, from outer appearances the lower midsection often holds excess fat that seems more stubborn than anything else above the waist. To trim your entire midsection, including the lower abs, start with regular cardio and a healthy diet. After that, these moves will help you slim down your lower abdomen with just a regular commitment and a little patience.
Lie on your back on a mat or soft surface to protect your vertebrae. Lift your legs so that knees are bent at a 90-degree angle, with shins parallel to the floor. Keep your arms straight and at the sides of your body.
Keep your upper body still and use your abs to raise your butt and hips off the mat, pulling your knees toward your face.
Squeeze your abs and knees until your knees are hovering over your mid-chest. If you feel strain on your lower back, do not contract your knees as far. Hold for one breath.
Return your legs slowly to the starting position. Do two sets of 10 to 15 repetitions. If this exercise becomes too easy, hold a small weight between your ankles as you do the move.
Position yourself on your back on a mat or soft surface. Keep your feet together and your legs straight as you lift your legs off the floor about 6 to 12 inches. Inhale and engage your abs. Keep your arms at your sides and your back pressed to the floor.
Lower your legs slowly as you exhale until your feet are 3 to 5 inches above the floor -- a little higher if you feel yourself straining or raising your lower back. Hold this position for one breath.
Inhale and raise your legs back to the starting position. Do one or two sets of 10 reps.
Lie face down on your mat or soft surface and slowly lift yourself to rest on extended arms and the balls of your feet with your feet together, as if preparing to do push-ups. This is the plank position.
Bring your right leg across the front of your body slowly -- without bending your arms -- by drawing your right knee to the left. Place your right foot on the inner area of your left knee. Allow your hips to twist naturally to accommodate the position, and shift your weight to the ball of your left foot. Keep your back straight and abs engaged.
Push your right leg back to the ground as you resume the plank position. Keep your back straight and abs engaged. Repeat the move on the left side of your body.
Do two sets of 10 reps, making sure that each rep includes both sides of your body.