TS-47 Pelvic Lifting

This week’s exercise is a little different than most of the other trunk stability training exercises we’ve covered thus far. It is taken right out of the DNS (Dynamic Neuromuscular Stabilization) playbook. It looks pretty simple but is quite difficult to execute properly. Essentially it is a reverse crunch where the ribcage is the fixed point and the pelvis is the moving segment. In biomechanics, we would call this reverse muscle action because the the more distal attachment is approximating toward the more proximal one. The reason this exercise is so damn challenging is because of the propensity to default into compensatory movement patterns, namely inhibition (insufficient activity) of the internal obliques (IO) and external obliques (EO) resulting in hyperactivity of the rectus abdominis (RA). The RA get’s a lot of attention, both good and bad, in the rehab and strength training communities. Aesthetically, it is everyone’s favorite abdominal muscle to show off - #SixPackAbs. In the functional rehabilitation world, it is often crapped on. This is most evident in Dr. Stuart McGill’s famous statement about the muscle “show me a 6-pack and I’ll show you a dysfunctional back.” The reality is, we evolved to have a RA, so we must need it in some way. Before I discus what exactly the RA does in function, let’s first discuss the myokinematics of trunk flexion. When we think of trunk flexion, we typically associate that with one muscle. You guessed it, the RA. Attaching to the sternum and the costal cartilage and inserting into the the pubic bone, it no doubt is powerfully positioned to create trunk flexion. It is, however, not the only muscle involved with this movements. Other muscles of note are the IO and EO. It is often thought that the hip flexors (psoas, rectus femoris, TFL, etc.) can produce trunk flexion, but this is not actually true. As their name indicates, these muscles affect the hip, not the trunk. Yes, the psoas major does have a teeny, tiny moment to produce trunk flexion, but this is inconsequentially small and only affects the lower lumbar spine. The reason the hip flexors are often conflated with trunk flexion is that they work with the abdominal wall to execute many traditional “core” exercises like sit-ups or a plank hold. In regards to pure trunk flexion (other than the psoas) they do not contribute in any way other than anchoring the pelvis in place so the abdominal wall can more efficiently produce trunk flexion. Trunk flexion should involve coordination between the the RA, the IO and the EO. (We can leave the pyramidalis out this for the time being.) Achieving this synchronicity is no easy task. That’s why hyperactivity of the RA is so common. The phenomenon necessary to achieve this synchronicity is intra-abdominal pressure (IAP). As an outward-pushing force within the abdomen, it is able to coordinate these muscles into one synchronous activation. In its absence, it is nearly impossible to achieve this coordination. The muscles that should be doing most of the heavy lifting (pun intended) are the IOs & EOs, not the RA, as is often thought. The RA is purely a sagittal plane muscle, significantly limiting its relevance outside the sagittal plane. Also, it only attaches to the medial aspect of the ribcage, lending it zero ability to move and affect the ribs. The obliques, on the other hand, are extremely broad and perfectly positioned to function in all three plane. Also, because they attach to the entirety of the lower rids, they are able to affect rib positioning. This is why it is so important to focus on maintaining IAP in any trunk stability exercise. You want to make sure that synchronicity of the abdominal muscles is preserved and, without it, such synergy is not possible. So besides looking cool, what does the RA do? Despite many rehabilitation professional’s proclivity to talk down about this muscle, it actually is quite important, but not in the way that you might think. Yes, it is able to assist with pure sagittal plane trunk flexion, but its importance has to do with assisting/improving the function of the IOs and EOs. The insertion of both the IO and EO (and the transverse abdominis) is a vertically oriented cartilaginous cord running between the pubic bone and the sternum called the linea alba. Each of the muscles attaching to the linea alba act to pull it apart. Here’s where the RA comes in. Running directly adjacent to the linea alba, it is able support the linea alba against the diastasis-creating pull of the abdominal wall. So, proper trunk flexion involves the RA as both a flexor of the trunk and a stabilizer of the linea alba to improve the trunk flexion capabilities of the EO and IO. What must be present is IAP. This week’s exercise is a challenging, but phenomenal way to train coordination of the trunk flexors via IAP. Best of Luck! Richard Ulm, DC #ProjectTrunkStability #AthleteEnhancement