Core stability training – A new point of view
An interesting critical review on core stability has drawn my attention lately.The myth of core stability is a critical review written by the Osteopath and Physiotherapist Eyal Lederman specialised in functional neuromuscular rehabilitation and functional stretching.
In his review, Lederman drew attention to the principles of core stability and the lack of evidence to support it. Core stability (CS) training was derived from studies that demonstrated that a change in motor control and recruitment of muscle fibre timings take place in people who suffer from back injury and pain. From there over the years a general belief about the importance of strong abdominal and back muscles has promoted some assumptions prevailing in CS training:
ASSUMPTION N. 1 – Certain muscles are more important for stabilisation of the spine that other muscles.
ASSUMPTION N. 2 – Weak abdominal muscles lead to back pain.
These assumptions refer to the role of transversus abdominis (TrA) muscle in increasing stability in the trunk of the body. The assumption also states that the human spine is an unstable structure that needs the activity of trunk muscles in order to keep an upright position. It is believed that TrA plays an important role in trunk stabilisation.
The TrA muscle has several functions. Its function is in synergy with the other muscles that make up the abdominal wall. It also acts in controlling other physiological features like pressure in the abdominal cavity, vocalisation, respiration, defecation, and vomiting1. The nerves serving the abdominal musculature are the same so it is impossible to contract voluntarily one muscle without contracting the others at the same time. Several studies did not find a link between weak abdominal muscles and spinal instability2. Also, damage to abdominal musculature does not seem to be detrimental to spinal stability or contribute to low back pain3.
ASSUMPTION N. 3 – Strengthening abdominal muscles reduce back pain.
While low back pain can lead to a loss of force in trunk muscles there is no proof that strong core muscles alleviate back pain. In fact, the activation of trunk muscles in walking is reported to be only 2% of the maximal voluntary contraction (MVC). In a standing position only 1% of MVC is required by trunk musculature rising up to 3% when a 32 kg weight is added to the torso (e. g. a heavy backpack). To date there are no studies that support that weak abdominal muscles cause back pain or that strengthening the abdominal muscles would reduce back pain4.
ASSUMPTION N. 4 – The existence of a unique group of muscles called “core” that work independently from other trunk muscles.
ASSUMPTION N. 5 – The timing of core muscles to decrease pain in the low back area.
This assumption is already explained in point number one. Trying to isolate and activate only one muscle in trunk area is impossible due to the fact that core muscles share the same neural pathway. An example would be when we perform a crunch exercise. Our brain won’t think “activate TrA or rectus abdominis”, but “bend the trunk forward”5.
In human movement the timing to contract muscles is organised ahead in anticipation of our intention. Try to learn or “re-learn” to contract a single abdominal muscle remains a theoretical concept6. All structures in our body are intimately connected anatomically and biomechanically in order to work together. Nothing “works alone”.
ASSUMPTION N. 6 – A relationship between core stability and back pain.
This assumption is also explained in point number one. Core stability exercise programs use an approach that does not take into consideration the biomechanical dynamics of the body. Low back pain is associated with factors like fatigue and overtraining combined with sudden, unexpected movements that are the cause of the injury. It is unlikely to see a benefit in further strengthening core muscles for injury prevention7.
In the last 20 years psychological and psychosocial factors have become important in assessing risks associated in back pain8. “How to use the body” in daily life activity has also become an important factor in preventing and treating low back pain. Biomechanical factors like muscle weakness and muscle asymmetry have been reduced in their importance in diagnosing, treating and managing low back pain9.
Based on my experience of training people with low back pain what is really important is to concentrate on the neurological reorganisation rather than the exercising of a single muscle of group of muscles. What is important is to learn how to use the body in complex movement rather than in a simple one. The concept of core strengthening is to work the muscle. Instead, we should work the brain in order to change the way how the brain sends signals to the muscles. However, there can be a time, maybe at the beginning of the rehabilitation program, where breaking down a complex exercise into a simple set of movements may help the person in understanding the concepts of neurological reorganisation.
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