Where is my Rectus Abdominis?
Your Rectus Abdominis is your “abs” located in the front of your belly. In anatomy, they consist of 2 parallel strips of muscles, but because there are tendinous intersections going through them, each strip can have between 2 and 4 muscle bellies, giving some people a 6- or 8- pack (Some people only get 4-packs! like Arnold).
Anterior abdominal region.
"rect-" = meaning raise/erect
"-us"= meaning “one who” (One who raises)
"Abdomin-"=meaning in the abdominal region of the body
"-is"=meaning a muscle
All together: The muscle who raises the abdominal region. You try sitting up from laying down with out using your abs!
Why This Matters
The abs are a powerful group of muscles and one of the primary movers in flexing the body trunk. They are critical in posture, which means in balance while standing, for stabilizing your trunk while lifting objects, for creating a wall for support of your internal organs, and for breathing. This means in almost every exercise, you are using your rectus abdominis in some way, shape, or form.
When you lift objects from the ground, be it your shoes in the morning, or a barbell deadlift, you recruit your core, including your rectus abdominis to stabilize your body and keep it sturdy under the weight. This serves to transfer your effort in your legs and back to up to your arms without losing energy or strength.
The rectus abdominis is also an important breathing muscle, particularly during exercise. When breathing normally at rest, you provide effort to inhale, but you relax to inhale, without much energy. This is because your body is stretchy like a rubber band and when you breath in, you stretch out your chest and stomach and when you breathe out it just goes back to its resting position. During intense exercise however, you don’t just relax to breathe out, you contract your abs and other core muscle to push the air out fast! This way, you can take a new breath sooner, and get more oxygen to your muscles more quickly. (Don’t believe me? try it right now, breathe out as fast as you can and feel your abs at work!)
It is important to maintain strong, healthy abs because, weak abs can lead to poor posture and back pain, especially when combined with other muscle weakness/imbalances. For example, weak abs can cause your pelvis to rotate forwards and down, called Anterior Pelvic Tilt. The result of this is the back of your pelvis shifting upwards, which compresses your low back creating an unhealthy “shelf-like” appearance. An exaggerated but good example is to look at the low back of an overweight/obese or a pregnant person. Generally, these populations do not have strong core muscles, and combining that with the extra weight that needs to be supported, the low back becomes compromised. So in addition to losing weight, strengthening your front can actually be a way to improve pain in you back.
On a Hamstring day:
Rectus Abdominis in Isolation: Any type of crunch mostion would isolate the rectus abdominis. This means that your pelvis should move relative to you rib cage. Your legs might also move depending on the exercise, but that is not necessarily the goal and might happen just by happenstance. Ex. Crunches, reverse crunches
Rectus Abdominis + Hip flexors: Many abdominal exercises inadvertently also target your hip flexors (Iliopsoas and rectus femoris). In these exercises the legs are moving in addition to the trunk and pelvis. The best example is the full sit up; in a sit up, the first portion is similar to a crunch, recruiting mostly your rectus abdominis, but very quickly your Hip flexors take over and your back stays relatively straight throughout the movement.
Hip Flexor dominant: While you may feel your abs tightening during some of these exercises, they are more working your Hip Flexors than your Rectus Abdominis. In many cases you just feel your abs tight because you are using them to stabilize your body while you are moving your legs. Hint: if you feel your legs moving but your pelvis and body are staying still, you are probably using hip flexors. There is nothing wrong with doing this, and in fact it can be very beneficial to work on your hipflexors for overall core strength. In addition, while you are not targeting your rectus abdominis primarily, sometimes holding them in static contraction can be just as or more difficult than some typical isolation exercises such as crunches! Ex: Laying or Hanging Leg raises, flutter kicks
Emphasis on Bodybuilding
Rectus Abdominis is a critical muscle in just about every division of bodybuilding in order to take home the title. The judges may want a specific look for them depending on the division, but they definitely are always looking!
For Bikini Competitors, you typically won’t want to come in as hard as a Men’s Physique, or as full as a Men’s Body Builder, but they must still have adequate definition. The abs should be prominent and defined when viewed from the front poses, but not projecting much when viewed from the sides. The goal is to maintain as small a waste line as possible, while still having some definition.
Women’s Figure/Men’s Physique is similar to Bikini in that you want to maintain a small waste line, especially as viewed from the side, but you want to have more deep cuts in your 6/8-pack than a bikini competitor. For men some projection is okay.
Bodybuilders typically have a good amount of girth to their rectus abdominis, even when viewed from the sides. Their fullness and width helps to balance the overall aesthetic of their large chests, legs, backs, and arms.
Pelvis: Pubic bone - Pubic symphysis and Pubic tubercle
In posture, and in most abdominal exercises, the pubic bone origin is often the anchor. As the pelvis remains still, the body moves towards the pelvis.
1) Sternum: Xiphoid process & 2) Costal cartilages: Ribs 5-7
In typical exercises, this is the attachment that does the moving. This is opposite however in handing exercises where the pelvis and legs move.
Linea Alba: central line connecting the 2 strips of rectus abdominis together. During pregnancy, this strip can sometimes loosen and cause a hernia. It is often corrected during a tummy tuck procedure.
Semilunar Line: Semi-circular line on the lateral borders of the rectus abdominis. Connects the rectus abdominis to the oblique muscles.
1) Flexes the Trunk: The primary action of the Rectus abdominis is to bend the torso down towards the pelvis.
The anatomical term for this is Flexion of the Trunk. This movement occurs at multiple joints, as all of the vertebrae of the spine must flex forward to accommodate the motion.
2) Stabilizes the Trunk: When working together with other trunk muscles, such as the Errector spinae, obliques, hip flexors, and quadratus lumborum.
When all of your core muscles contract simultaneously, the trunk becomes stiff, and able to translate forces well from the legs up to the arms.
The Rectus abdominis is a secondary breathing muscle. It helps in forced exhalation; in other words when you breathe out on purpose, or during exercise or other period of increased breathing rate.
When a muscle acts as antagonist, it is trying to resist the action of a different muscle. Since the rectus abdominis acts in trunk movement and breathing, it has 2 different opposing directions as well. The major antagonists are the Errector spinae and Diaphragm.
The deep back muscles (Errector spinae) is the primary extensor of the torso, and acts to bend the body backwards, and maintain standing posture, therefore it opposes both of the actions of the Rectus Abdominis.
The Diaphragm is the muscle of inhalation, therefore it opposes the Rectus abdominis in exhalation.
The Rectus abdominis is innervated by several spinal nerves corresponding to their dermomyotome. These span from T5-T12.
Theses nerves also innervate the skin over the muscle (thus dermomyotome). Each spinal nerve comes from the spine, and wraps around the body and ends at the rectus abdominis in the midline.
The Rectus abdominis is primarily supplied by inferior epigastric artery. This is is a branch of the External Iliac Artery inside the pelvis. whichFemoral Artery which supplies the Quadriceps femoris in the front of the leg. The inferior epigastric artery travels upward along the deep inside surface of the muscle. It continues upwards and anastomoses with the Superior Epigastric Artery. The Superior Epigastric come down from the inside of the chest wall, a branch of the internal thoracic artery (aka internal mammary artery in females).
Heart -> Aorta -> Common Iliac -> External Iliac -> Inferior Epigastric supplies Rectus abdominis
Heart -> Aorta -> Subclavian -> Internal Thoracic -> Superior Epigastric supplies Rectus abdominis