We’ve all done it. I’ve pointed to the top half of my abs to show a client where my “upper abdominals” ended and where my “lower abdominals” began. The truth is I just didn’t know any better at the time. That didn’t make me a bad person or even a bad trainer; it just meant there was something I wasn’t quite sure about. So where do the upper abdominals end and the lower abdominals begin? The answer is a lot simpler than you might think.
Abdominal muscles are differentiated between upper and lower by which part of the torso they move. Upper abdominals depress the ribcage and curl the thoracic spine into flexion (your upper torso), while lower abdominals control the pelvis (your lower torso). All abdominal muscles work together to provide stability to the midsection. However, exercises like posterior pelvic tilts and crunches are not the same in regards to recruitment patterns. A crunch, when done properly, is an exercise that primarily utilizes your upper abdominals (internal obliques and the rectus abdominus). The posterior pelvic tilt, when done properly, is an exercise that primarily utilizes your lower abdominals (external oblique muscles).
What about rotation? Rotation is primarily a function of the abdominal obliques with secondary assistance from a variety of other core stabilizers and movers more intrinsic to the spine. Pure rotation is a function of synergistic contraction between both upper and lower abdominals (internal obliques and external obliques) with stabilization provided by the transverse abdominus and the rectus abdominus. The external obliques are used on the side opposite the rotation while the internal obliques are used on the side the rotation is towards. Pure lateral flexion is a function of both the internal and external obliques working synergistically on the same side. In this case the quadratus lumborum is also at work.
Axe chops (from left to right) primarily engage the external obliques on the left and internal obliques on the right. Axe chops (from right to left) will primarily engage the internal obliques on the left and the external obliques on the right. This is one simple way to ensure your client’s upper abdominals don’t become over developed compared to their lower abdominals. We see this muscle imbalance in our office weekly in low back pain patients even though it is easily prevented.
Thank you Chris Ostling PT, DPT for your assistance with this installment