In 2007, Professor Eyal Lederman wrote an article entitled “The Myth of Core Stability” for the online journal Centre for Professional Development in Osteopathy which you can download here. But for those with less time on their hands, I will summarise his fine points which we will discuss in Yoga Class this week…
Essentially this is a critique of the wide spread acceptance since the 90’s that we now blame low back pain on a lack of core stabiity. Bracing the trunk before loading the spine has been the mainstay of activities in the Pilates Movement with a view to preventing back injury as well as a cure for back pain which Lederman argues has been based on a misunderstanding of research.
In the first instance, Lederman argues against there being a core of muscles which are used just to stabilise the spine which work independently from surrounding muscles to protect the spine when moving. The transverse abdominis (TrA) has a particular focus in Pilates Classes, however, he points out that when this muscle is damaged (or in pregnancy when it is extensively elongaged) it does not automatically result in lower back pain for the individual. Even when the rectus abdominis is cut during breast reconstructive surgery, individuals were not shown to experience an increase in lower back pain as a result of this new weakness. According to Lederman:
“We can conclude from the above that healthy abdominal musculature can demonstrate dramatic physiological changes, such as during pregnancy, post-partum and obesity, with no detriment to spinal health. Similarly, damage to abdominal musculature does not seem to impair normal movement or contribute to LBP.”
He also explains how the Pilates Movement made a “dramatic leap of faith” when they based a whole industry on identified issues with the timing of the engagement of the TrA which was seen to be slowed in those with CLBP (Chronic Lower Back Pain). He argues that the delayed or differentiated recruitment pattern of muscles is a protective mechanism rather than a fault.
In the original studies, the muscle strength of the TrA was not measured but the timing of it’s recruitment was. The difference between pain free ad CLBP individuals was only one fiftieth of a second. Hardly significant!!!! His argument that these timing issues have been addressed in the Pilates Movement using kneeling and lying exercises in which the core is trained to be braced constantly in order to address the issue of the timing of when the TrA is recruited (if it’s on all the time, then timing is no longer an issue). Lederman says that this fruitless activity is “like aspiring to play the piano faster by exercising with finger weights or doing slow push ups”. He is also at pains to point out that many of these exercises are not transferrable to real life situations in which the trunk is expected to play a part in stabilising the spine so if you learn a set of exercises to control the trunk whilst lying on your Pilates Mat, there is no guarantee this is going to transfer into your every day life activities (lifting shopping into the boot of the car for instance). It is quite impossible to maintain concentration on one group of muscles whilst performing every day actvities despite attempts to get students to concentrate on their core all day long!
The Pilates Movement is based on two arguably false assumptions:
1. That core stability will protect the back from injury and pain
2. That those with CLBP all have weakend trunk muscles
In fact the amount of bracing required to protect the back under load is very minimal in order to be effective and core muscles would have to be very severely ruptured in order for the spine to be affected. According to Lederman:
“During standing and walking the trunk muscles are minimally activated. In standing the deep erector spinal, psoas and quadratus lumborum are virtually silent! During walking rectus abdominis has a average activity of 2% maximal voluntary contraction (MVC) and external oblique 5% MVC. During standing “active” stabilisation is achieved by very low levels of co-contraction of trunk flexors and extensor, estimated at less than 1% MVC rising up to 3% MVC when a 32 Kg weight is added to the torso. With a back injury it is estimated to raise these values by only 2.5% MVC for the unloaded and loaded models. During bending and lifting a weight of about 15 kg co-contraction increases by only 1.5% MVC”.
Often in class, we observe that this contraction isn’t under our conscious control. So when we pop up (ha ha) into a Plank, the core just switches on of it’s own accord – there is no need for us to brace first…. It has not been shown that deliberately strengthening these muscles through Pilates Style exercises has any effect on decreasing lower back pain in numerous studies.
In relation to the second point above, Lederman explains that there is no evidence that those with CLBP do indeed have weakened abdominal muscles and certainly the injury is very unlikely to affect just one group of isolated muscles, such as TrA therefore separating this muscle consciously for the purpose of building it up to protect the spine makes no functional sense at all.
In Core Stability (CS) Training, the excessive use of the contraction of the abdominals may also detract from functional movements. An example of this is when you attempt to side bend whilst gripping on to your trunk muscles – the side bend is necessarily reduced. A soft belly and deep breath (not possible with a tight core) will allow for a far wider range of movement.
It could also be argued that training individuals to excessively contract their abs might also worsen back pain in cases where the injury was caused by overly loading the back through lifting or sports related activities since they are already overly bracing themselves during these activities. Excessive contraction increases intra-abdominal pressure which in turn puts pressure on the back and results in a worsening of the spinal compression which in turn leads to increasing back pain. Any form of gentle exercise (especially Somatic Yoga) will lead to an improvement in the person’s psychological as well as physiological and functional ability and CS training has not been shown to be more effective than any other movement work.
Lederman also points out that psychological issues play a far greater role than core weakness in the recurrence of pain in lower back injuries. There is a tendency to worry and catastrophise about accidentally worsening the injury. Tensing abdominal muscles is associated with anxiety and worry and it could be argued that this contributes to the injury further as the person self inflicts reduced back movement which stiffens the joints and increases inflammation.
Professor Peter O’Sullivan further points out that we have created a widely accepted cultural belief in the West (not evident in say, Africa, where people are carrying around all their worldly possessions on their backs) that the back is very vulnerable and that pre-tensing before movement is desirable which he explains in this clip, is very detrimental to our recovery in LBP.
Direct Link to Lederman’s Research: