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| Abdominal Training: Unstable Maybe Better! | |||
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By Mark Nemish |
August 2004 | ||
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Whether one trains for professional sports or just for the fun of it, a common thread that runs throughout everyone’s training is the desire for a “6-pac” of abdominals. Such development of the mid-section is only achieved when the proper combination of genetics, diet, and training come together. The training aspect of the sought-after “6-pac” encompasses conditioning exercises designed to burn calories, and thus fat, surrounding the abdominals, and secondly, the proper strengthening exercises to form or shape the muscular aspect of the abdominals. There is however a tremendous amount of misinformation surrounding the proper training of these muscles as evidenced by the deluge of infomercials as seen on TV. Everyone claims to have the latest devise that will not only shed inches off your waste, but also make you coffee in the morning. Stop listening to the imitators on TV, stop spending your money on useless pieces of equipment, and start listening to scientific research. This article will focus on the results of a very recent research article (Vera-Garcia et al., 2000) comparing the abdominal muscular recruitment of curl ups performed on either a stable or unstable surface. In future articles I will expose the myths surrounding some of the devises currently invading our airwaves (Ab-shaper/Ab-roller and Ab-Flex) and also outline exercises and movements that are the most effective and safest for the development of your abdominals. But first, I will provide a short background of the individual muscles that comprise the abdominal wall. The anterior (front) abdominal wall consists primarily of four muscle groups, the rectus abdominis (what most people consider their abs to be), the external oblique, the internal oblique, and the transverse abdominis. All four muscles have different roles or functions and are maximally recruited in slightly different ways. Each of the muscle groups however, acts as stabilizers for the lower back and thus their strength are important for injury prevention of the spine. For the purposes of this article the first three muscles will be the focus.
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The rectus, representing the “6-pac-look”, originates and inserts on the pubic bone and the ribs. It’s main function is to flex the trunk by bringing the pelvis and ribcage closer together (Norris, 1993). Both oblique muscle groups are primarily located on the left and right sides of the abdomen and are more active in twisting actions although both are active in flexing the truck as the rectus abdominis does (Norris, 1993). Vera-Garcia et al. (2000) examined and compared the recruitment of these three muscle groups when performing curl-ups (crunches) on a flat stable surface (bench) or on 3 variations of unstable surfaces. The first two conditions on the unstable surfaces consisted of performing curl-ups on a gym ball (also called a physio or swiss ball) with the feet either on the floor or up on a bench. Performing curl-ups with the upper body on a wobble board and the feet on the floor comprised the third unstable condition. A wobble board is a round wooden disk with a rubber ball underneath that is used mainly in ankle proprioception (balance) rehab. Electrodes placed over the surface of the upper and lower rectus and oblique muscles detected the recruitment of the abdominal muscle groups. The electrodes pick up the electrical activity of the muscle and the whole procedure is referred to as electromyography (EMG). For each of the conditions, the subjects performed a curl up in which their head and shoulders were raised and held for 6 seconds in the curl up position. A number of interesting and significant findings occurred with this research study. First of all, performing curl ups on a gym ball with the feet on the ground resulted in a greater than twofold recruitment of the rectus abdominis than when performed on a stable bench whereas the activity of the external oblique increased about fourfold. Internal oblique recruitment was also nearly twice as active in this unstable condition. The differences between the two conditions for the lower portion of the rectus and external obliques were statistically significant (p<.05). Furthermore, it was found that in each of the four conditions of curl-ups, there was no significant difference |
between the recruitment of the upper and lower rectus abdominis. In other words, the argument that the upper abdominals are preferentially recruited in a curl-up was not supported in this study. Both the lower and upper fibers of the rectus were recruited to the same degree. And finally, this study demonstrated that the rectus is more recruited than the obliques (especially the external ones) during the execution of a curl-up, regardless of the stability of the surface. Performing a curl-up exercise on a gym ball increases the recruitment of three of the anterior abdominal wall’s muscle groups. Because the surface that the exercise is being conducted on is unstable, it can be hypothesized that the body’s response to falling off this surface is to increase the recruitment of the rectus and especially the external oblique muscles, thus increasing the stability of the lower back. Since the external oblique displayed the greatest increase in recruitment when performing curl ups on an unstable surface (400% increase), a gym ball may promote greater co-contraction of the anterior abdominal wall. This certainly has important implications for enhancing spinal stabilization and thus injury prevention. And finally, for all those whose main goal is the “6-pac” look, performing your crunches on a gym ball will increase the effectiveness of your abdominal workouts thus possibly owing to a faster means to your goal of shapely abs. Gym balls can be purchased in a number of sporting goods stores for as little as $30.00. Given the results of this scientific study, it may be a wise investment to make. Look for future articles to be written on the science behind abdominal training. Train hard, but smart, watch what you eat, and condition your body to burn calories and you will achieve the abs you can be proud of while at the same time staying injury-free! References: Norris, C.M. (1993). Abdominal muscle training in sport. British Journal of Sports Medicine, 27, 19-27. | |
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