To The Core
The latest, greatest thing since sliced bread in the exercise performance and rehabilitation fields has to be what is most often referred to as “core training.” Alternately known as core strengthening, core stability, spinal stabilization, dynamic stabilization, neuromuscular retraining, neutral spine control – this concept has more names than the average rap artist whose career lasts more than two years!
Despite the variations in terminology, the basic theory behind all of these is fairly consistent. Proponents of core training assert that strengthening of the deep muscles of the trunk and pelvis bestows benefits on the individual by:
- Increasing biomechanical efficiency of the spine,
- Providing a more stable base of support that will allow more powerful extremity movements, and
- Decrease the risk of injury, especially to the lower spine.
Core training is not a new concept. In the 1920’s, Joseph Pilates talked about developing a “girdle of strength” by recruiting the deep trunk muscles. His ideas have regained popularity in recent years and have been incorporated into a popular exercise regimen that bears his name. Physical therapy education programs have for years taught the concept that stability of the proximal trunk is necessary for efficient mobility of the extremities. While early advocates focused on the lumbo-pelvic musculature as the “core,” in recent years this has been expanded to include the scapulo-thoracic (shoulder girdle) area.
Because the definitions and notions on core training – by whatever name – are so similar and consistent, and because there are so many of them, this concept has become another in a long line of theories that has been readily accepted by the health and fitness industries. From a conceptual standpoint, it certainly sounds reasonable and there is no really good reason to doubt the claims made by those who advance these ideas. But once again, we must ask whether it is enough to believe a theory simply because it sounds good, or should we demand more solid, scientific evidence to support it before we sign on.
Surprisingly, for an idea that has been around as long as this one, there is a marked paucity of good evidence to substantiate the claims of its proponents. (Part of the problem may be that, while there is general agreement on the concept of core training, there is a lack of consensus as to what exactly constitutes an actual core strengthening program. In other words, there is a considerable degree of disparity in the exercises prescribed by different “experts.”) In fact, I could not find a single, good study to support the claim that core strengthening enhances athletic performance, or that training of trunk muscles even improves the strength of the upper or lower extremity muscles.
On the other hand, there have been a few studies that have looked at the relationship between core strength and injury prevention. Leetun et al took measurements of several trunk and hip muscle groups in athletes (80 male and 60 female) prior to their seasons (track and basketball). At the end of the season, they compared those who had reported an injury during the course of the season with those who had not, and found that the athletes with greater hip strength had significantly less injury occurrence. Nadler et al, however, found no significant difference in the occurrence of low back pain in athletes before and after the incorporation of a hip strengthening program.
Physical therapists often use very specific trunk strengthening exercises in the treatment of low back and shoulder injuries and there is a growing body of evidence that this is effective. However, there is little good evidence that core stabilization exercise prevents such injuries.
Hopefully, the passage of time will produce verification of the claims of those who believe fervently in this theory. In the meantime, those who choose to engage in this form of exercise can at least take some solace in the knowledge that there is no evidence whatsoever that core stabilization regimens are in any way harmful.