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Of all the myths floating around in the wide world of fitness, one of my favorites is the legend of the “upper and lower abs.” One of the reasons this ranks high on my list is because even though its so easy to debunk, this myth is so persistent, that it just refuses to go away.
Hundreds of years of anatomical research are conveniently brushed aside in seconds by every late night infomercial selling the latest gadget or contraption to help sculpt, tone or chisel your lower abs for a perfect washboard, six-pack stomach. And, it’ll do it in less than five minutes a day, for as little as three payments of $39.99.
The simple truth is there is no such thing as upper or lower abs. They are one and the same, just plain old abs, or more accurately the Rectus Abdominis muscle.
The Rectus Abdominis runs the length of the abdomen from the Xiphoid Process (the bottom tip of the sternum) to the Pubis bone (in the pelvis). It is split into right and left halves, NOT upper and lower halves. These right and left halves are separated by the Linea Alba, a thick band of connective tissue, and also crossed by three fibrous bands that give the appearance of the six-pack. In rare cases, some individuals may have a fourth fibrous band, resulting in an eight-pack configuration.
Where the myth of upper & lower abs first came from I am not totally sure. But if we take a closer look at how muscles contract we might be able to shed some light on the subject.
Skeletal muscles generally have at least two ends that attach across either side of at least one joint. When the muscle contracts it shortens, pulling on these two ends, which in turn, pull on the bones, they are attached to, causing one or more of the bones to move. Many times, one of the ends, the origin, is attached to a bone that is stable or doesn’t move. The other end, the insertion, is the one where you see the most amount of movement. This is the case with the Rectus Abdominis.
The main function of the Rectus Abdominis muscle is flexion of the spine. The spine is made up of 33 individual bones allowing you to flex it at many different points. So when you flex one portion of the spine, a certain end of the Rectus Abdominis is moving, while the other end remains stable to allow for this movement. This does not mean that only one part of the muscle is working, it means that the ends are working differently.
So the muscle as a whole may contract differently in certain areas, depending on the exercise. For example, while performing a classic crunch with your lower body stationary, the upper portion of the Rectus Abdominis may contract with stronger force than the lower half. Or if you were performing a reverse crunch, where you bring your knees into your chest while keeping your upper body stable, the lower portion of the Rectus Abdominis is contracting differently than the upper. Also, there are a few nerves that innervate different sections of the Rectus Abdominis, which can result in these sections being activated separately.
It is also important to note here that the Rectus Abdominis attaches at the hip, not the legs. Therefore you are not using your abs when you raise your legs either in a lying or hanging position. This movement is performed by the hip flexor muscles, which lie deeper than the abs.
There are some studies that appear to show that certain exercises are more effective for the lower portion of the abs than others. Scientists from the University of Nebraska Medical Center used electromyography (EMG) to measure abdominal muscle activity during various exercises, including the trunk curl, reverse curl, v-sit, and twist curl. Their findings suggest that a greater emphasis may be placed on the upper or lower portions of the Rectus Abdominis, depending on the exercise performed.
All this means is that there are a variety of exercises that activate the Rectus Abdominis muscle in different ways. All the more reason to use a progressive program that has plenty of variation with exercises that target all planes of motion, joint angles and muscle activation patterns.
There you have it – the infamous upper & lower abs are in fact all just one muscle. So next time you hear someone tell you they know a great exercise to target your lower abs, you can give them a little anatomy lesson. Unfortunately as long as there are late night infomercials, there will always be the MYTH of upper and lower abs.