Review
Therapeutic Exercise for Lumbopelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back (C Richardson, P Hodges, J Hides.
pub. Churchill-Livingstone, second edition 2004).
Diagnosis and Treatment of Movement Impairment Syndromes (S A Sahrmann.
pub. Mosby 2002).
The first edition of Richardson et al, published in 1999, is reviewed in Stretching exercises and the low back Part IV: Etiology of mechanical low back pain and the implications for stretching. The basic principles reviewed in the first edition concerned the relation of low back pain to segmental instability and the role of local muscles in providing what in general terms has become known as ‘core stability’. The 2004 edition extends the analysis incorporating research findings on the role of weight-bearing and non weight-bearing muscles and the inter-play between these and local core muscles. The conclusions drawn from the new research, derived from micro-gravitational work (i.e. weightlessness in space) strengthen the author’s original thesis that segmental instability is related to low back pain that can be prevented and remedied by strengthening the local muscle system.
The authors reiterate their earlier work that focuses on the correlation of muscular-skeletal pain with joint instability. This built on research by Panjabi (1992a and 1992b who described a ‘neutral zone’ in which movements of the spine needed to be stabilised by local muscles attached to the spine. Ligaments and passive structures control spinal movements at the end of range but held no influence in the neutral zone. Larger muscles situated more laterally produced movements of the spine of the spine but whilst they provide ‘global’ stability in the back that are unable to provide core support and fine tuning of the spinal segments. Control and stability at the neutral zone are by the local muscles of the lumbo-pelvic area with multifidus being particularly important. These deep local muscles have their insertions or origins attached to the lumbar vertebrae and control inter-segmental motion and local stabilization. The global muscles handle the external loads placed on the trunk, so minimizing the variations in load imposed on the local muscles to manageable levels. Ligaments and other passive elements limit motion only at the outer ranges of joint movement although their role as proprioceptors influence local muscle movements The neutral zone becomes larger with injury or muscle weakness and smaller with increased muscle force.
Multifidus provides lumbar segmental stability linking vertebrae to vertebrae within the lumbar and between lumbar and sacral vertebrae. It finely adjusts spinal movement and enhances stability by stiffening motion segments. Facet joints are covered by multifidus on all sides except where the joints are in direct contact with ligamentus flavum so the multifidus muscles keep the joint capsules taut and prevent impingement of articular cartilage. Multifidus has by far the most influence on spinal segmental stability but can only do so in conjunction with efficient functioning of the other elements of the ‘corset’. These are the transverses abdominis, the pelvic floor muscles and the respiratory diaphragm. The functional activities of multifidus is linked to transversus abdominis with both acting as synergists as integral components of a corset that imposes intra-abdominal pressure. The pelvic floor muscles and respiratory diaphragm contribute to this corset. Transversus abdominus also has considerable influence on the tension of the thoracolumbar fascia facilitated by its extensive attachments to it. The thoracolumbar fascia is thought to constrain radial expansion of the multifidus and the lumbar longissimus and iliocostalis muscles. This provides a brace around these muscles that enhances their strength contributing to spinal stiffness and lumbar stabilization.
The authors quote research findings that patients with low back pain have been found to have abnormal degenerative changes in the multifidus. It is atrophied with muscle fibres containing a larger proportion of fat, it fatigues more easily and is unstable in concentric activity. Patients also have delayed contraction of transversus abdominis in preparation for movement of the limbs that suggests inadequate motor control. The link between muscle function and spinal stiffness provide a basis for therapeutic exercise to be used to manage spinal instability offering an exercise strategy based on co-contraction of the multifidus, transversus abdominis, the pelvic floor muscles and respiratory diaphragm aimed at promoting segmental stabilization to treat mechanical low back pain. Muscle stiffness as described by the authors is muscle with a spring like quality in resisting deformation and able to return to its original position after lengthening. Muscle stiffness is generated by the activation of tonic, postural slow twitch motor units. The quality of stiffness is a function of the ability of the central nervous system to control the motor units adequately. It is therefore necessary to train the central nervous system as well as strengthen the muscles concerned. Muscle stiffness may be compromised by fatigue, degenerative changes or injury. Damage to spinal structures can, in turn, result from instability and manifest as pain.
The principles extolled by Richardson et al guide their approach to ‘segmental stabilisation training’ that involves training muscle performance and re-education of control by the central nervous system. In essence this means acquiring and refining movement and co-ordination. A key aim is to strengthen local muscles of the lumber segments relative to the global muscles. The patient needs to become aware of the muscles initially through palpation in a fully supported lying position. This is followed sequentially by training the muscles in closed chain, then open chain positions and movements leading to training in muscle control in functional activities.
Patients can find palpation and activation of the multifidus difficult and the authors offer descriptions of using electronic feedback devices as an alternative. However, as transversus abdominis(TA) and the pelvic floor muscles are synergists to multifidus, patients unable to directly perceive multifidus contraction may find it easier to work this muscle by way of working the synergists that may be more easily perceived and controlled. The ideal position to palpate transverses abdominis and test its contractile strength is described as medially and inferiorly to the anterior superior iliac spines lateral to the rectus abdominis. With the patient supine, contraction of TA can be perceived as a deep tension in the abdominal wall that develops slowly. The internal abdominal oblique muscles that lay over the TA should remain relaxed whilst contracting TA. Activation of the oblique muscles will be felt as a more rapid and superficial tension. The former feels as though the abdominal wall is sinking beneath the palpating fingers. The latter feels as though the muscle is hitting out against the fingers. Contraction of the TA should also result in a perceived narrowing of the waist. Furthermore, contraction of the oblique abdominal muscles result in pulling the ribs downwards and inwards compared with the upward and outward movement that occurs with contraction of TA whilst the other abdominal muscles are silent.
Contraction of the respiratory diaphragm contributes to the internal pressure system protecting and stabilising the spine. The pelvic floor muscles also contribute to the development of this internal pressure. Contraction of these muscles may is easier at the end of a relaxed exhalation. The patient should focus on the anterior part of the pelvic floor (described as if trying to stop a flow of urine) in order to activate the pubococcygeus muscle. The patient should not contract the puborectalis and should therefore avoid contraction around the anus.
The authors point out it is not possible in therapeutic practice to isolate the contraction of TA. However, whilst all abdominal muscles are activated in voluntary expiration, relaxed breathing can decrease the activation of the global muscles, i.e. the rectus abdominis and the abdominal obliques. This enables greater focus on TA sp it is preferable to approach initial training of TA with relaxed breathing, although this is less practical when the training is progressed into functional activity. Similarly, there is better co-activation of TA with contraction of the pelvic floor muscles when the lumber spine is in a neutral position. However, the techniques are intended for use in functional activity in many different body positions. This should be approached incrementally so once the patient has achieved good control of the local synergy muscles in a lying down position the training can progress to sitting and standing positions with attention to correct spinal curves. The correctly held lordosis is achievable only with effective contribution from the core local muscles and is not sustainable by using the global muscles alone. Once trained, the local muscle control is integrated into closed chain i.e. both feet on the ground weight-bearing functions. The closed chain exercises challenge the patient to maintain stability of the local muscles and also maintain appropriate spinal curves whilst moving and elevating the upper limb. An example is a squat or a lunge that can be progressed by adding shoulder flexion and holding weights. Performing postures and movements on unstable surfaces provide further challenge.
Most everyday functions and sport activities involve open chain movement whereby at least one foot is off the ground. Core local muscle control with suitable hip and spine positioning therefore needs to be maintained with limbs on a stable trunk such as kicking a ball. This example requires the hips to move rather than the lumbar spine. An easier less dynamic exercise such as standing on one leg with arms raised may be practiced before attempting more dynamic functional activities. The spine maintains its normal curves in this posture but training needs to progress to include normal spinal movements if the spine is to aid dissipation of forces and work with maximum efficiency. The role of the local muscles is thereby to protect and control individual spinal segments whilst the global muscles dissipate force and generate movement. The main focus at this stage is to integrate the local, global, weight-bearing and non weight-bearing muscles with the body in action. The author warns that it is at this stage that patients with a history of low back pain tend to revert to previous unhelpful patterns of muscle control so counter-measurers need to be planned.
The major addition to the second edition of the book is an account of the influence of the global muscles on the quality of function of the local muscles. Global muscles control or influence spinal movements although they are not directly attached to the spine. The authors describe important distinctions between global muscles that are weight bearing and those used more for dexterity and are generally non-weightbearing. The former are mostly one-joint extensor muscles comprised of relatively more slow-twitch fibres suitable for maintaining posture. The latter are used for grasping, manipulation and dexterity and are principally two or multi-joint flexor muscles with fast twitch fibres. Research in micro-gravity has found non-weight bearing muscles to become stronger whilst weight-bearing muscles lose strength as a result of de-loading. This change in strength ratio has an adverse effect on the quality of motor control of the local core muscles. Balance is therefore necessary between the strength of the weight-bearing and non-weight-bearing muscles and also between the strength of weight-bearing muscles and the core local muscles. Local core muscles should fine-tune spinal segmentation movement within the ‘core-zone’. Failure of the local muscles to do imposes pressure on the passive structures that can result in pain. Poor control of the local muscles will result in strong global muscles compressing the spine and imposing gross movements. Global muscles therefore need to be maintained at an optimal level in balance with the local muscles.
Lack of weight-bearing activity of the postural extensor muscles will result in their reduced strength and change their functional orientation to fast-twitch thereby reducing their efficiency in postural control. Furthermore, an increase in proportionate use and strength of the multi-joint fast-twitch non weight-bearing flexor muscles has the effect of reducing the efficiency of the motor units of the weight bearing muscles that in turn has a detrimental influence on the local muscles.
The authors of this work predict that the principles they described may also be used in treatment of muscular-skeletal pain in other areas of the body. Adequate strength and correct patterns of motor control and muscle recruitment in vastas medialis and the rotator cuff muscles are prerequisites for stability in the knee and shoulder joints respectively. Within the context of their current studies the authors prescribe a general strengthening of weight-bearing one joint extensors and a relative reduction in the relative strength of multi-joint flexor muscles. Whilst the weight bearing muscles need to remain supple, the implication is that the multi joint non-weight bearing muscles require enhanced flexibility, that is they need to be stretched relatively more than the weight bearing extensors. There appears to be little rationale for stretching muscles concerned with stability unless they are pathologically short. The practical implications for the postural and exercise therapist such as myself appears to be the need to enhance motor control of the core muscles whilst emphasising the strengthening of the weight-bearing extensors muscles and the suppleness of the multi-joint flexor muscles.
Sahrmann’s Diagnosis and Treatment of Movement Impairment Syndromes (2002) provides a volume of diagnosis and treatment for the entire muscular-skeletal system. It is quoted in Richardson et al (2004) as providing examples of postural exercises appropriate for incorporating spinal segmental stability training. Sahrmann explores the development of faulty posture and pain resulting from muscle weakness and imbalance including analysis for the hip and shoulder joints as well as the spine and proposes a novel approach to diagnosing joint dysfunction by categories of impaired movement. The text describes the adaptation of tissues to posture and everyday movement activities and how correcting faulty body mechanics may alleviate muscular-skeletal pain. The premise is that joints work most efficiently with least wear and tear when running in good alignment. Imbalances of strength and length of muscles servicing a joint results in joint misalignment and consequent movement impairment. The text describes relevant symptoms and their relation to impairments in alignment, muscle recruitment, stiffness, length and weakness. An examination protocol is proposed and treatment programmes are offered accordingly consisting of principally stretching and strengthening exercises.
The text offers useful illustrations and descriptions of ideal posture contrasted with common defects and their associated pathology. It also echoes two prominent themes discussed in the Richardson et al (2004) text. Firstly, it emphasises control of the abdominal muscles to maintain spinal stability in open chain movement exercises. Sahrmann does not specify work on the transverses abdominis but her instruction to ‘pull the navel towards the spine’ (p438 and other pages) is similar to ‘pull in the lower abdomen’ decreed by Richardson et al (p 181 and others). Secondly, Sahrmann offers an example how ‘local’ muscles that would normally provide joint stability can weaken and become overwhelmed by more distant ‘global’ muscles that move the joint in less precise alignment. Sahrmann does not use the terms ‘local’ or ‘global’ but their use here draws attention to comparison with the Richardson et al thesis. The actual example used by Sahrmann refers to muscles used in hip extension. Gluteus maximus and piriformis are normally the dominant muscles in hip extension. Their proximal attachments provide more precise control of the femur in the acetabulum maintaining a relatively constant position of the femoral head than the hamstrings muscles are able to do. This pattern may be altered if the gluteus maximus becomes weak and the hamstring muscles become stronger and dominant. The hamstring muscles do not attach to the femur except for the short head of bicep femoris that attaches distally on the femur. The hamstring muscles cannot, therefore, exert precise control of the head of the femur that may then glide anteriorly in the acetabulum during hip extension causing stress on the joint capsule. This syndrome is mirrored in the shoulder joint when the supraspinatus is weak relative to the pro-rata strength of the deltoid. Supraspinatus is unable to hold down the head of the humerus resulting in impingement. Unfortunately there appears to be nothing in the literature offering techniques to isolate the supraspinatus for strengthening purposes. It may be possible to use the techniques of palpation to train the supraspinatus in a similar way to that described by Richardson et al for training the multifidus.