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The Lateral Subsystem

Have you ever wondered why it's generally more difficult to balance on a single leg when holding a weight on the opposite side of your body? Or have you experienced right-sided low back pain when standing on your left leg? The answer to these issues may be related to your lateral subsystem.

The lateral subsystem is a group of muscles that work together to provide support and movement in the frontal plane, which is a plane that divides the front of your body from the back of your body. The primary muscles that make up this subsystem include the gluteus medius muscle, the leg adductor muscles and the contralateral (opposite) quadratus lumborum muscle:

As you can see in the picture above, this subsystem requires that certain muscles in the legs work with muscles of the trunk/core. When you perform an activity while balancing on a single leg , it's the gluteus medius and adductors (the muscles on the right leg in the picture above) that work together to keep the leg stabilized, while the opposite quadratus lumborum (the muscle on the left side of the trunk in the picture above) works to keep the trunk stabilized. Without the co-activation of these muscles, your pelvis would drop and become misaligned. Changes in pelvis or hip alignment can often indicate dysfunction of this subsystem, which is a common dysfunction that we see in the clinic as it relates to low back pain and hip pain.

When it comes to balancing on one leg and holding a weight on the other side of your body, the lateral subsystem is stressed in a way that requires good muscle mechanics and activation. If this subsystem is not integrated properly and muscles are not properly activated, you may have a loss of balance, weakness and/or pain in either the hip or low back. Performing exercises while balancing on a single leg can be very effective at training this system. One of our favorite exercises to perform is the pass-over exercise, which is a great way to work on single leg stance stability and develop core muscle control. Grab a weight and hold it in one hand. Start by balancing on one leg with the opposite leg in front. Slowly pass the weight from one hand to the other, making sure you keep your core muscles engaged. Pause after you’ve passed the weight:

This post is just scratching the surface on a technical and important subsystem in your body. This subsystem does not act in isolation with many of daily activities we perform; however, isolating this subsystem can better assist other subsystems in promoting more effective movement. If you have any questions or concerns, please don't hesitate to call us at 907-622-2500. We would also love to hear from you if you have any issues that you think might be related to this subsystem. Finally, we would like to thank Brent Brookbush from the Brookbush Institute for inspiring this post. For more information about the institute, click here.

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