Core Concepts: Part II
Moving With Your Core
This is the second part of a three part series on trunk stability. In the first part we discussed the importance of bracing the right way through your trunk by using the diaphragm. The second part will revolve around dynamic stability of the core through bracing and movement.
At least once a day, and in most cases, a very large amount of times during the day, we perform activities that require trunk stability. We bend down to pick things up, we carry something, we reach across our body or overhead to pick up a useful item. Without the muscles involved in those movements being trained regularly, we can develop either acute or chronic injury.
The trunk both braces and moves in several different ways using a variety of muscles. In the second part we will examine what these movements are and what muscles make them happen. For the sake of time we will highlight the most important details of these muscles as they relate to trunk stability.
Flexion/Extension and Anti-Flexion/Anti-Extension
Probably the most recognized form of trunk movement is flexion/extension and the counter movement which is anti-flexion/anti-extension. This movement involves either allowing the trunk to flex or extend at the thoracic or lumbar spine. Bracing would be the trunk preventing those movements from occurring.
The primary muscles involved in this are rectus abdominis, the erector spinae, and the multifidus. The Rectus Abdominis is a long muscular strap extending from the ventral lower sternum to the pubis. The main action for rectus abdominis is flexion of the trunk (flexion of thoracic and lumbar spine), while it works by drawing Symphysis and Sternum toward each other. The Erector Spinae is often described as a group of different muscles called Iliocostalis, Longissimus and Spinalis. They are the chief flexors of the vertebral column. They straighten the flexed vertebral column and can also bend it posteriorly. They also release during its flexion so that the movement is slow and controlled. You can see through its description how important these muscles are to keeping your spine healthy through both movement and bracing.
The last muscle, the Multifidus is a series of small muscles which travel up the length of the spine. It is an important muscle in the rehabilitation of lower back pain and can have an extraordinary impact on your body. It allows for the proper distribution of body weight across the spine and activates even before any action is carried out to help protect the spine.
Think of bending down to pick something up or reaching up and grabbing something off of a shelf, these muscles that were discussed will help keep that precious spine of yours nice and safe. This is probably the most commonly practiced type of trunk focused movement in everyday life and in the gym. Unfortunately, too much of our time is spent training this movement in the wrong way. More time should be spent preventing flexion/extension than performing it.
Rotation and Anti-Rotation
The next movement/countermovement is rotation/anti-rotation. This is the act of rotating the trunk or preventing said rotation. The primary muscles involved are the obliques and the transverse abdominis. Both sides of the obliques, the internal and the external both included, flex the vertebral column by drawing the pubis towards the xiphoid process. Unilaterally (one side) it results in side flexion and contralateral rotation . Basically it helps facilitate and prevent rotation. The transverse abdominis wraps horizontally from the back of the body to the front. The Transverse Abdominis function is to maintain tone of the abdominal organs; when one side works it bends and rotates the body to the side.  When you reach across your body to grab something or you get pulled quickly to a side you are using these muscles to facilitate and also to stop these movements.
Lateral Flexion and Anti-Lateral Flexion
The last movement/countermovement is lateral flexion/anti-lateral flexion. The primary muscles involved in this include a lot that we have already covered like the Rectus Abdominis, the Obliques (internal and external), and the Erector Spinae. The other major muscle(s) are the Quadratus Lumborum. The Quadratus Lumborum fixes the 12th rib to stabilize diaphragm attachments during inspiration. It also laterally flexes the vertebral column and extends the lumbar vertebrae. It forms with the contralateral Tensor Fascia Lata (TFL) and Gluteus Medius a lateral myofascial sling which aims to maintain frontal plane stability of the pelvis . So next time you successfully carry a bunch of groceries in one hand, thank your Quadratus Lumborum for protecting your back. This movement/countermovement requires a lot of interconnecting parts between the legs, hips, and the back. Due to its high frequency of usage in everyday activity, this should be a staple in your programming.
These movements and countermovements make up way too large of a part of our daily activities to ignore. We must be able to move and to brace. They must each be trained consistently and intelligently in order to protect ourselves both in every day life and in our physical activities from compound lifting to walking/running, bike riding, hiking, etc.
Join us for the last part of the series where will discuss how to program these exercises throughout your workouts.
This article does not necessarily represent the views/opinions of MadLab Performance, LLC. This article is not meant to recommend health solutions in place of a doctor or other medical professional and should only be used to help those reading it gain more information prior to making their own decision.
Josh has experience with anything and everything, from prenatal and postpartum care to coaching high school athletes as they prepare for high-level DI careers. He specializes in getting the most out of whoever he is coaching. Josh is the Head Coach for MadLab Performance and manages the company’s personal trainers. He also is a frequent contributing writer for MadLab’s continuing education articles. Josh may be contacted by email at: email@example.com
1. Helen J.Hislop Jacqueline Montgomery,Muscle Testing,2007,8th edition.
2. Drake RL, Vogyl AW, Mitchell AW. Gray’s anatomy for students. 3rd edition. Philadelphia: Churchill Livingstion Elsevier; 2015. 286p
3. Cheng J, Jarvis M. Quadratus Lumborum . http://radiopaedia.org/articles/quadratus-lumborum. Accessed August 9, 2019.