Your diet has a lot to do with your ability to display a ripped abdominal wall. However, you must also kick up your cardio to eliminate fat stores in that area. And when it comes to training, select three good abdominal exercises; one that emphasizes your upper abdomen, one for the lower area of your abdominal wall and one that provides constant tension on both upper and lower regions and the sides of your abdomen. Seated knee-ins accomplish the last goal very nicely. To sharpen your abs, you need exercises that tighten and not stretch your entire abdominal wall. Many exercises will emphasize the superior (upper) or inferior (lower) parts of your abdominal wall, and a few target the lower areas of your abdomen, but few exercises provide the constant tension that activates both the superior and inferior parts of your abdominal musculature. Seated knee-ins activate the sides, upper and lower portions of your abdominal wall very effectively. If your body fat levels are not too high, seated knee-ins will chisel your abs to a razor sharp condition in a short time.
Structure and Function
The rectus abdominis is a long, strap-like muscle. It’s the primary vertical muscle of the anterior abdominal wall. It’s separated vertically in the middle by the linea alba, so the abdominal wall appears to have a left and right half. The linea alba is a tendinous sheet that’s about one-half an inch wide that stretches from the xiphoid process on the inferior border of the sternum (sternum = breast bone) to the pubic bone in the pelvis. The rectus abdominis begins on the pubic bone and pubic crest, which is the center of the pelvic bones of the hip girdle. This muscle inserts into the xiphoid process at the base of the sternum and some fibers terminate on the cartilages of the fifth to seventh ribs (near the sternum).
The rectus abdominis has tendinous intersections (connective tissue) that create the grooves when it’s tensed. Although there is some genetic variability in this “six-pack” look, usually there are three sets or rows of these tendinous intersections. The muscle fibers of the rectus are actually quite short compared to some muscles (like the biceps) and they run almost entirely vertical from one small tendinous line to the next. Therefore, when the rectus abdominis is tensed, the short fibers bulge between the tendinous grooves, almost like small ropes. The thicker the muscle fibers, the greater their rounded rope-like appearance in each block of tissue. When both right and left halves of this muscle contract simultaneously, the trunk is flexed forward so the head and chest move closer to the hips and legs (assuming a fixed pelvis).
The external oblique is the largest and most superficial of the three flat abdominal muscles. It begins along the lower half of the ribs by small bundles of muscle fibers. The muscle fibers run from lateral to medial, the same direction your fingers would point if you put your hands in your pockets. This muscle inserts into the pubic and iliac bones of the pelvis and also the linea alba. When both left and rights sides of the external oblique muscles contract, they flex the trunk so the head will move toward the feet. If only one side contracts, the trunk will flex toward the opposite side. For example, if only the right side contracts, the external oblique will twist the trunk and shoulders toward the left side of the body.
The internal oblique is deep to the external oblique muscle and it’s therefore not visible. It begins from a thick connective tissue sheath located in the lower back, called the thoracolumbar fascia, and also from the iliac bone of the hip. Its fibers run at right angles to the external oblique muscle, fanning out from their origins and running toward the head (superiorly). The internal oblique inserts into the lowest three or four ribs, where they become continuous with the internal intercostal muscles (respiratory muscles of the rib cage). In contrast to the function of the external oblique, the internal oblique will twist the body toward the right if only the right side contracts, and toward the left if only the left side of this muscle contracts. However, similar to the external oblique muscle, the internal oblique will flex the trunk at the waist and move the head toward the feet, if both left and right portions of the internal oblique contract together.
Seated Knee-Ins
This exercise should not be confused with straight leg raises, which primarily activate the lower regions of the abdomen. Seated knee-ins activate the upper regions and a pelvic lift ensures that the lower part of the abdomen is also activated effectively. Furthermore, muscle tension is maintained in both superior and inferior regions of the rectus abdominis and oblique muscles from the beginning to the end of each set in seated knee-ins.
1. Select a flat exercise bench. Turn you body sideways so that your legs are 90 degrees to the long axis of the bench on which you are seated.
2. Grab the edge of the bench behind your back with both hands for support.
3. Lean back on the bench just slightly. Put both feet together and lift them from the floor. Raise your legs and thighs until they are parallel to the floor.
4. Bring your knees toward your chest. Tense your abdomen and exhale as your knees approach your chest. This is like a version of an abdominal crunch. Hold this position for a count of two. The upper part of the knee-ins will also induce a pelvic tilt that will ensure activation of your lower abdominals. If your knees can touch your chest, you can separate your legs on the way up toward your chest, so that each knee passes to either side of your rib cage.
5. Extend your knees and straighten your legs to full extension as you inhale. Stop only momentarily, then flex your knees again and bring them toward your chest.
6. Try to complete five sets of 50 repetitions before ending the set. Rest for 45 seconds, then start your next set. You should be able to work up to five sets. When five sets becomes too easy, strap on some medium weight ankle weights to add resistance for additional sets.
Training Tips
Since you don’t need any special equipment, you can do a few sets of these just about anywhere, even in your bedroom before turning in for the night.
There are several technique errors you should avoid. First, it’s important not to lower your legs below parallel to the floor. Likewise, if your legs are lifted more than five degrees above parallel to the floor, the resistance will be easier, but the activation of the lower abdominals will be reduced significantly. Also, lowering too far will stretch the rectus abdominis and enlarge this muscle, and who wants to have a bigger and thicker abdomen? If the fibers of the abdomen are stretched excessively, the stomach will take on a rounded and almost bloated, protruding look when relaxed. Thirdly, if you lift your legs with your knees locked out straight (a seated leg raise), this will strongly activate your iliopsoas muscle and this will reduce the activation of the rectus abdominis and oblique muscles. This is because the iliopsoas, a deep abdominal muscle, is one of the strongest flexors of the lumbar region.
If you want to increase activation of your oblique muscles, twist your legs to the left (twist slightly from your hips) on one repetition and to the right on the next repetition when you’re bringing your knees toward your chest. It’s a good idea to eliminate holding your breath at any point during the exercise, since this increases the intra-abdominal pressure and prevents the abdominal fibers from shortening as much. Rather, exhale as your knees are coming toward your chest, and inhale as your legs are extended.
Few abdominal exercises allow such a constant tension throughout your entire abdominal wall as does seated knee-ins. You should achieve a very intense continual muscle burn throughout much of the exercise, but you must persist through the burn to achieve ultimate abdominal success. This selective fiber activation and shortening will be the keys to producing razor-sharp abs.
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