The only thing worse than losing a client to an injury is losing a client to an injury you caused!
About 30 years ago, we learned that straight-legged sit-ups were bad for us because it caused back pain. But aren't lying or hanging leg raises the same thing as the straight legged sit-ups done in reverse? Aren't we using the same muscles, whether we raise our legs and keep our upper body still or raise our upper body and keep our legs still?
Great-looking abs are desired by both men and women, but lying or hanging leg raises are probably the worst exercise you can instruct someone to do unless you are a chiropractor or physical therapist and hope to make money from their rehabilitation.
Why It's Bad
To understand why this movement is bad, you need to understand the basic biomechanics of how muscles contract to move the body. Anatomy and physiology taught us that a muscle attaches at two ends. When those two end points come closer together, we get muscle contraction. It is the contraction of the muscle that pulls the end points closer. When the two end points move further apart, the muscle relaxes and stretches.
For example, look at the bicep muscle. It attaches at the top of your shoulder and just below the crease of your elbow. When you bend your arm or do a bicep curl, the two end points move closer together. When you straighten your arm the two points move further apart.
Every muscle in the body works by this same "pulley" principle, including our eye muscles. Look at the chest muscles. The pecs attach along the side of your sternum and run diagonally into the top of your shoulder. As you lower the bar when doing bench press, the two end points move further apart. The pec muscles are stretching. As you push the bar off your chest, the two end points move closer together. This causes the pec muscles to contract.
Examine the Leg Raise
The muscles responsible for raising the legs are the psoas muscles, known as the hip flexor, not the abdominal muscle. The hip flexor attaches at the upper portion of your thigh muscle and sits beneath your abs and intestines and runs up and attaches to your spinal column, or more specifically, your lumbar vertebra and disc. These muscles are notoriously known for being the primary cause of back pain.
The abdominal muscles sit on top of your intestines and attach at the bottom of your ribs and run down past your belly button and attach to the pubic bone. Remember: A muscle contracts when the two end points come closer together.
To prove to you that lying/hanging leg raises don't specifically work the abdominal muscles, lie flat on your back as if you were preparing to do a leg raise. Place your right hand at the top of your pubic bone and your left hand on the bottom of your rib cage. Now slowly raise your legs up to the ceiling to 90 degrees. Did your hands come closer together? I don't think so!
If you keep your legs in that vertical position (90 degrees) and now pull them closer to your head. You will notice that your pelvis will begin to rock up towards your head. You should begin to feel your hands come closer together. Now you are doing a reverse crunch, and your abdominal muscles are actually being exercised.
Lower your legs; keep your hands on the same positions, legs bent, feet flat on the floor, and do a regular crunch. Your hands should come closer together, which tells us that your abdominal are going through their full range of motion and are contracting and stretching the same way we contract all the other muscles on our body.
Hopefully, this will explain why crunches and reverse crunches are the best exercises to do for your abs. All you have to do is raise your shoulders a few inches off the ground or raise your pelvis towards your shoulders, and you'll get a great isolation movement that targets the abs. Doing leg raises, holding your feet six inches off the ground or having someone throw your legs back down after your raise them is only going to make your hip flexors tighter and put you and your clients at risk for back pain.
I see it so often; patients come to my office complaining of back pain. I ask them if they sit all day, sleep in the fetal position, take long trips, or I ask them what kind of ab workout do they do. If they say lying or hanging leg raises or some other type of similar movement, I gently apply slow, deep pressure (with my fingers) into their hip flexors, which are found about two inches to the side of their belly button. Nine times out of 10 they come screaming off my table. This tells me their hip flexors are in spasm, and the continual contraction from doing leg raises is only making matters worse.
Leg raises are okay as long as the starting point begins with legs bent at the waist (90 degrees) the legs are pulled up about 20 degrees and then back down to 90 degrees. You don't want to lower it past that starting point, otherwise you are using your hip flexors to pull them back up to 90 degrees, and we don't need to be making those muscles any tighter.
When you do a leg raise, the first 90 degrees of the leg raise is activating the hip flexors. When you go past 90 degrees, the abdominal muscles begin to contract and are responsible for raising the legs any further. Unfortunately, most people do their leg raises within that first 90 degrees of range of motion, which is only going to make them susceptible to lower back pain.
It doesn't matter if you bend your knees or put your hands behind your back. The muscles responsible for raising your legs those first 90 degrees are your hip flexors, not your abs. So don't put your client's health or your financial security at risk by making them do an exercise that could injure them and prevent them from continuing as a client.
I know people have been promoting leg raises for years, but when you look and understand the basic biomechanics of how the muscles work, you will see why they don't target the muscles we think. Go grab your A&P book and take a look at where these muscles attach to better see what we are talking about.
Dr. Len Lopez (www.DrLenLopez.com) is a nutrition and fitness expert and author of To Burn or Not to Burn Fat is the Question and the inventor of The Work Horse Fitness Trainer. He is the host of Action Steps for Health and a frequent guest on radio and television. His approach to health and fitness is based on TEE-times: Time, Energy and Effort.