Core Training has become a widely used term in the fitness and strength & conditioning fields, but it seems that many people have substituted the term “core training” for abdominal training. There seems to be a need to clearly define what the core is to eliminate this confusion.
The core is a collection of muscles that co-contract to stabilize the spinal column and maintain proper alignment during body movements. The core includes the abdominals, the back extensors, the upper back (Lats and Rhomboids), and the muscles of the pelvis (mainly the Glutes). If all the core muscle are strong, then the spine is stable and can bear large loads and stress with less risk of injury.
If one focuses on just strengthening one or two of these muscles, the abs and back extensors for example, the spine becomes less stable as the muscles of the upper spine become the weak link in the chain. The key is developing a balance of strength for all the muscles that support the spine, not just the abs.