Core stability, core strength and their relationship with back pain have been subject to research since the early 1980s. Research has highlighted the benefits of such training for people with back pain and for carrying out everyday activities.
The whole area of core stability, exercise and lower back pain is far more complex than the media or the average gym instructor would have you believe
However, these findings, combined with general beliefs about the importance of abdominal muscles for a strong back as well as influences from Pilates, have promoted several assumptions, such as that certain muscles are more important than others, or that weak abdominal muscles lead to back pain.
Other assumptions are that strengthening abdominal or trunk muscles can reduce back pain, that there is a unique group of core muscles working independently of other trunk muscles, that a strong core will prevent injury, and that there is a relationship between stability and back pain.
As a consequence of these assumptions, a whole industry grew out of these studies, with gyms and clinics worldwide teaching the abdominal hollowing and core bracing exercise to athletes for prevention of injury and to patients as a cure for lower back pain.
In essence, the passive human spine is an unstable structure and therefore further stabilisation is provided by the co-contraction of trunk muscles. Erroneously, these muscles are often referred to in the core stability approach as the core muscles and assumed to be a distinct group, with anatomical and functional characteristics specifically designed to provide stability.
One of the muscles in this group to have received much focus is transversus abdominis. It was widely believed that this muscle was the main frontal component of trunk stabilisation. It is now accepted that many different muscles of the trunk contribute to stability and that their stabilising action may change according to varying tasks.
In one of the early studies, it was demonstrated that during rapid arm or leg movement, the transversus abdominis in patients with lower back pain was delayed in its recruitment. It was consequently assumed that the transversus, by means of its connection to the lumber spine, is dominant in controlling spinal stability. Therefore any weakness or lack of control of this muscle would spell trouble for the back.
It was in part the results of this study that led to the huge success of Pilates globally, as it embraced these findings and started busily retraining the delay in recruitment of transversus abdominis.
However, the subject is far more complex than this and many other factors have to be considered. Mainly though, just because transversus abdominis is the first muscle to fire up does not make it the most important – it just means that it is the first in a sequence of events and all muscles need to be considered.
No study to date has demonstrated that core stability exercise will reset onset timing in patients with lower back pain – therefore if using this as a tool to address lower back pain, one should be cautious, especially if an individual therapist promotes it wholeheartedly as the answer to one’s pain.
There is more confusion about the issue of trunk strength and its relation to back pain and injury prevention. What we do know is that trunk muscle control, including force losses, can be present as a consequence of back pain or injury. Again, here several assumptions are often made: that loss of core muscle strength could lead to back injury and that increasing core strength can alleviate back pain.
To what level do the trunk muscles need to co-contract in order to stabilise the spine? The answer is not very much. During standing and walking, the trunk muscles are minimally activated and this is very important to understand when deciding on the appropriateness of an exercise. These low levels of activation raise the question as to why strength exercises are so often prescribed when such low levels of co-contraction forces are more necessary in the rehabilitation of the spine. Such low co-contraction levels suggest the strength losses are unlikely ever to be an issue for spinal stabilisation. A person would have to lose substantial trunk muscle mass before it will destabilise the spine.
Is there a relationship between weak abdominals and back pain? No studies to date have shown that strengthening the core muscles, in particular the abdominal muscles and transversus abdominis, would reduce back pain and therefore you should proceed with caution when trainers or therapists suggests that is does.
The whole area of core stability, exercise and lower back pain is far more complex than the media or the average gym instructor would have you believe. The first thing to note when considering this area, and in particular core stability and lower back pain, is that there is no gold standard universal measure or definition on what core stability is, which makes writing any article on it problematic and leaves it open to ambiguous interpretation.
The majority of expert opinions state that more research needs to take place especially when exercise is used as a tool for lower back pain. From the research it is unclear which exercises are most effective, which exercises are essential, and at what point there are diminishing returns from continued progression.
Bryn Kennard is a Pilates instructor at Bodyworks.