There are numerous claims about the effectiveness of various abdominal exercises. One misconception is that certain exercises such as leg lifts or leg raises specifically target your lower abs. Leg lifts don't work your lower abs, though other exercises that involve raising your legs may enable you to focus more on the lower portion of your rectus abdominis, commonly called your abs.
Getting To Know Your Abs
Your abdominal muscles consist of the rectus abdominis, transverse abdominis, and the external and internal obliques. The rectus abdominis is the flat band of muscle that runs down the front of your trunk between your lower sternum and your pubic bone. The external obliques, sometimes called the love handles are on either side of the rectus abdominis. The internal obliques run at a right angle beneath the external obliques. The transverse abdominis are deep-lying muscles that help hold your internal organs in place.
Your Abs Are Not Sectioned
When performing some ab exercises, you may feel that your rectus abdominis is divided into two distinct sections, but according to Len Kravitz, Ph.D., of the University of New Mexico, your rectus abdominis work as a whole and you can't contract each section independently. However, when you perform ab exercises like crunches that only move your trunk with your lower body immobilized, the muscles of the upper portion of your abs contract harder than the lower portion. Conversely, ab exercises that involve immobilizing your trunk and lifting your legs should work the lower portion of your abs harder.
The Illusion of Leg Lifts
When you do leg raises or leg lifts, your entire abdominal wall isometrically contracts to stabilize your legs and protect your spine. According to ExRx.net, leg lifts work your iliopsoas -- one of your hip flexors. The iliopsoas lie beneath the lower portion of your abs. Isometrically contracting your abs and engaging your iliopsoas cause muscle fatigue in your pelvis area. The fatigue and burning in the area is often mistaken as your lower abs working, notes ExRx.net.
Crunching from the Bottom Up
To focus on the lower portion of your abs, do reverse crunches. This exercise involves lifting your legs and pelvis and, according to Dr. Kravitz, contracts more muscle fibers in your lower abs than your upper abs. To perform reverse crunches, lie on your back with your legs raised at a 90-degree angle to your body. Bend your knees and cross your ankles. Pull your knees toward your chest by raising your hips and pulling your pelvis toward your rib cage. Do three sets of as many reps as you can.
This Chair Is Not for Sitting
A study commissioned by the American Council on Exercise conducted at the bio mechanics laboratory of San Diego State University looked at the effectiveness of 13 different ab exercises. The study found the captain's chair was the second most effective ab exercise. The exercise involves stabilizing your upper body and bracing your back against the captain's chair with your legs dangling down. Lift your legs and pull your knees toward your chest by tilting your pelvis forward and raising your hips. As you are moving your lower body with your trunk immobilized, the captain's chair leg lift engages more muscle fibers in the lower portion of your rectus abdominis. Do three sets of as many reps as you can. If you don't have access to a captain's chair, do the exercise hanging from a pull-up bar.