Q: I went to an exercise physiologist for some help with a shoulder/scapula problem. She was adamant that I have to do a core training program as part of the rehab. Is this just a craze or is it really all that important?

A: Core training (strengthening the muscles of the belly and trunk) has become quite popular but for good reason. The more we learn about the influence of the center stabilizing areas of the body, the more we realize how important core strength is to movement of the arms and legs.

The core includes: the abdominal muscles (in particular the transverse abdominis), the deep muscles of the spine (multifidus), and the hip flexors (iliopsoas muscle).

Looking at the body as a whole, the core is made up of the lumbar spine, the pelvis, and the hip joints. This area is also called the lumbopelvic-hip complex. Any of the structures that cause or prevent motion in these areas is part of the "core." There is also evidence to show that the scapula (your shoulder blade) plays an important role in the kinetic chain (connection between the core and the extremities).

For example, when using the arm overhead, there is an entire sequence of actions needed. First, there is a ground reaction force as the foot and leg push against the ground. This force moves through the legs to the knees and hips and then into the trunk. The legs and trunk produce about half of the energy and force needed for this motion.

The trunk and scapula (wing bone) then work together to funnel this force to the shoulder, arm, and hand. This allows the smaller muscles of the arm and hand to position the hand to control the movement. Each activity has its own kinetic chain and energy. You cannot move the arm without core control so your exercise physiologist is right on with this approach!

Reference: W. Benjamin Kibler, MD, et al. Scapular Dyskinesis and Its Relation to Shoulder Injury. In Journal of the American Academy of Orthopaedic Surgeons. June 2012. Vol. 20. No. 6. Pp. 364-372.