Core exercise training has become very popular in the United States over the last five years. The core muscles refer to deep muscles of the trunk (spine and abdomen). These include the iliopsoas (hip flexor), lumbar multifidus (LM; spinal muscle), and transverse abdominis (TrA; abdominal muscle).
Electromyography (EMG) studies have shown that these deep muscles are impaired in people with low back pain (LBP). They may be weak and atrophied. Atrophy means the muscle fibers are getting smaller in size. The muscle contraction then gets weaker.
Impairment of the core muscles also means there is delayed activation of the muscles when needed. Slow contraction alters movement and can lead to pain and injury. There is also a lack of voluntary control of the core muscles.
This understanding has led to the motor control theory of spinal stabilization. This theory suggests that core training strengthens the deep trunk muscles. This type of training works to alleviate LBP because these structures control motion between the vertebrae.
With core exercises, patients are able to learn how to activate and train the deep trunk muscles.