Updated: Jul 2
The Abdominal Complex
Let me be clear from the start. This is NOT a “how to” on getting 6-pack abs for the summer season. However, it will help establish a foundation for a strong core through the following objectives:
1.) Highlight the origin, insertion, and action of each abdominal muscle as to understand the biomechanical principals of targeting the abdominal complex.
2.) Create a relationship between biomechanics and a variety of abdominal exercises as to more thoroughly understand proper joint movement vs compensatory joint movement.
3.) Review concepts to assist with targeting of the abdominal complex during exercise and common compensations to observe to prevent inefficiencies from developing.
When referring to the abdominal complex it will include the transverse abdominis, rectus abdominis, internal obliques, and external obliques. Developing abdominal complex (and overall core) strength can have far reaching benefits past an aesthetically pleasing 6-pack. For starters it will create spinal and pelvic stability to move heavier loads during strength training exercises, such as the squat and deadlift. Through targeted strengthening we can develop improved awareness. By being more aware of our abdominals we can improve posture immensely. This may even result in decreased chronic pain due to corrections in biomechanics. Additionally, by creating stability through the spine and pelvis we are decreasing the stress on joints that can lead to spinal degradation and pelvic dysfunction. By learning to connect to the abdominal wall effectively we can create greater efficiency with exercises and workouts!
Nearly all muscles have an origin and an insertion point on a boney surface, a place where they act on a joint to produce movement. When a muscle contracts it produces force that facilitates this joint movement. For example, a bicep muscle originates on the scapula (shoulder blade) and inserts into the elbow joint. When a bicep contracts it can pull on and move the scapula, shoulder, and elbow joint (biomechanics). This means that each muscle of the body has a particular job when contracting to produce movement. The abdominal complex follows this rule just the same. Although each abdominal muscle has very specific points of origin and insertion, they all follow a common theme of connecting the anterior (front) of the pelvis and the ribcage (with minor connections to the posterior trunk chain). Therefore, abdominal contractions will only produce specific movement (or stability) through the trunk, pelvis, and ribcage. Another way of thinking of this concept is to target the abdominals during exercise we must produce movement through the pelvis and/or ribcage! Excessive hip joint, lumbar spine, and cervical spine movement are considered compensations leading to improper targeting of dozens of additional muscles and creating inefficiencies with exercises and workouts.
Move to the end of the article for a deeper dive into abdominal complex anatomy including insertion and origin points along with actions of each muscle.
A Deeper Connection Through Palpation
To better understand the biomechanics of the abdominal complex, ribcage, and pelvis it can help to palpate the region being targeted. Through touch we can visualize how the muscles facilitate joint movement. Luckily this anatomy is accessible and can be easily explored!
Specifically, splay out your hands across the abdominal region (palms down) placing pinky fingers on the front tip top of the pelvis (ASIS), thumbs on the lower ribcage, and remaining fingers on different parts of the abdominal wall. Feel for the space between the ribcage and pelvis decrease and the different abdominal muscles contract when performing pelvic rotation or ribcage depression. You may notice the difficulty or intensity of the exercise increase as that space becomes smaller. This is also known as abdominal compression which will be reviewed later on.
Conceptualizing Abdominal Function
Also known as the act of pressing together this concept is highlighted by the ability to decrease the space between the ribcage and pelvis. As the space decreases the contractile strength of the abdominal muscles increases. This can lead to improved range of motion and mobility and unlock the ability to perform more complex body movements. To visualize compression, think about folding the body in half pulling the chest towards the legs.
The difference between bracing and compression is dependent on movement. Bracing involves a submaximal isometric (no movement) contraction of the abdominal wall and can increase intra-abdominal pressure. This is helpful when stabilizing the pelvis or spine is required due to excessive movement or hypermobility. Bracing is most often utilized compound, heavy load exercises such as the squat, deadlift, shoulder press, or pull-up but is also an important concept when stabilizing the plank.
Proper diaphragmatic and abdominal breathing is a complex, coordinated task that often requires deep mental thought to perform correctly and consistently. During any abdominal exercise it is strongly encourage to focus breathing through, not around, the tension developed in the abdominal complex. Breathing will initially feel shallow and restricted, but with concentrated practice, will become easier and more efficient. Referring back to Anatomical Connections many of the abdominal muscle’s actions involved breathing, specifically expiration.
Pelvic Floor & Adductor Synergy
The abdominal complex and pelvic floor share a synergist connection. When recruited together they can produce increased activation and movement through the pelvis. A simple way of promoting this synergy is to target the adductor magnus muscles. Without over complicating things the adductor magnus can be recruited by squeezing the knees or thighs together. Coordinating a knee squeeze, posterior pelvic rotation, and ribcage depression will promote greater abdominal and pelvic floor activation for strengthening.
Anterior Pelvic Rotation & Lumbar Extension
These two compensations go together like peanut butter and jelly. The hip flexor muscle group’s (rectus femoris, iliacus, psoas, sartorius) main action is to flex the hip. However, due to abdominal weakness they can have a strong influence on the pelvis promoting anterior pelvic rotation and lumbar spine extension. This can lead to deactivation of the abdominal complex and place compressive stress on the pelvis and lumbar spine. Proper movement through the lower body during abdominal focused exercises should be initiated and dominated by posterior pelvic rotation and lumbar flexion. In fact, hip flexion through the hip joint should remain as minimal as possible. The most effective tactile cue to maintain this joint position is to sense the low back pressing into the ground and the tailbone (sacrum) tilting upward toward the ceiling. Additionally, make sure to include ribcage depression to stabilize the upper body. Work to increase the pressure and range of motion of these three movements.
During a crunch does the initial movement come through the trunk or neck? Stability vs mobility will be covered more in-depth below but for now it is important to understand the primary moving parts during abdominal exercises are the pelvis and ribcage. This will help lead to the conclusion that the cervical spine must remain stable with movement being initiated through ribcage depression. To connect more clearly imagine lifting the chest towards the knees and keep the chin retracted back. A little trick is to hold a tennis ball under the chin throughout the exercise. The pressure of the scapulas (shoulder blades) on the ground will decrease as pressure of the low back into the ground will increase. This compensation most likely occurs due to the weight of the head overloading the strength of the abdominals. Protracting or flexing the cervical spine effectively decreases the load on the abdominals making the exercise easier to perform but at the cost of cervical muscle and spinal strain.
Bracing Without Breathing
The inherent benefits of abdominal bracing were discussed above. However, bracing combined with dysfunctional breathing can have negative consequences. When it comes to abdominal focused exercises repetition is often preferred. Higher repetition calls for increased oxygen consumption as it shifts from anaerobic to aerobic. Without proper breathing oxygen uptake does not occur and muscles are unable to work for longer periods. This directly affects cardiovascular endurance, muscular endurance, and caloric burning. In the Guide to Muscular Tightness & Pain the positive effects of breathing on promoting a parasympathetic nervous system response was highlighted. It can create a calming effect on the body that allows for increased focus and concentration through managed stress levels.
Similar to the compensations seen through the cervical spine, the knee’s flex (or bend) during lower body abdominal exercises due to an excessive load placed on the abdominals. With the quadriceps engaged and knees fully extended the weight of the lower body increases placing a greater load on the abs. This can result in the above compensation of anterior pelvic rotation and lumbar extension. Before advancing a lower body exercise, such as the leg raise, or adding weight make sure to overcome this compensation. Not only will abdominal strength improve but so will quadricep strength and hamstring mobility.
Mobility vs Stability
Mobility vs stability is a very common theme when it comes to a whole-body approach of exercising and biomechanics. Each abdominal exercise falls into one of four categories. In the sub section of each category an example exercise is listed. Note that no other joint movement is listed in this section.
1.) Ribcage Mobile; Pelvic Stable
2.) Ribcage Stable; Pelvic Mobile
a. Leg Raise
3.) Ribcage Stable; Pelvic Stable
4.) Ribcage Mobile; Pelvic Mobile
1.) Hooklying Lumbar Press
2.) Hooklying Knee Tucks
3.) Table Top Pelvic Tucks
4.) Table Top Initial Crunch
5.) Table Top Heel Touch
6.) Table Top Pelvic Rotations
1.) Hooklying Sit-Up
2.) Elevated Leg Raise
3.) Shoulder/Elbow Side Plank
4.) Elbow to Knee
5.) Seated Balance
6.) Elbow & Knee Plank
1.) V-Up Sit-Up
2.) Hand to Toe
3.) Seated Balance Rotations
4.) Seated Balance Knee Tucks
5.) Hill climbers
6.) Elbow & Foot Plank
1.) Star Plank
2.) Strict Hanging Leg Raise
3.) L – Sit
4.) Seated Balance Toe Touch
5.) Front Levers
Internal Surface Ribs 7-12
Anterior Portion Iliac Crest
Portion of Internal Oblique
Bilateral (Both Sides Contract) = Abdominal Compression; Breathing Expiration
Unilateral (Single Side Contracts) = Trunk Rotation (Same Side)
Costal Cartilage Ribs 5-7
Anterior Portion Iliac Crest
Inferior Ribs 10-12
Bilateral = Trunk Flexion; Abdominal Compression; Breathing Expiration
Unilateral = Lateral Trunk Flexion (Same Side); Trunk Rotation (Same Side)
External Surface Ribs 5-12
Anterior Iliac Crest
Bilateral = Trunk Flexion; Abdominal Compression; Breathing Expiration
Unilateral = Lateral Trunk Flexion (Same Side); Trunk Rotation (Opposite Side)
Note: Parts of origin, insertion, and action were left out for simplicity sake.
Thank you to KEN HUB for providing all anatomical photos in this educational article.