Different Muscles, Different Roles

When designing an exercise program, it is necessary to understand that certain muscles are designed for stability, while others are for movement and force production.

Bergmark, A. Stability of the lumbar spine: A study in mechanical engineering. Acta Orthop Scand 1989;60:Suppl.230

Bergmark differentiates the concept that certain muscles surrounding the lumbar spine play different roles. The larger muscles that we tend to exercise at the gym are known as ‘global’ muscles..while the smaller muscles that connect more vertebrae to vertebra are called ‘local’ muscles.

‘Global’ muscles such as the rectus abdominis, external obliques, and latissmus dorsi are designed for force production, movement and torque. While the ‘local’ muscles such as the lumbar multifidus and transversus abdominis are designed for intersegmental spinal stability. In daily function we need an interplay between ‘global’ and ‘local’ muscles so that we are able to stabilize the spine, while movement occurs.

In core stability training, we need to design programs that can specify muscle contractions of both groups of muscles. General programs tend to focus too much on the larger global muscles and do not specifiy ‘local’ muscle contractions.The use of real-time ultrasound imaging provides the most direct visual feedback to the client how to contract the deeper ’local’ muscles that are difficult to see from the superficial skin.