Drop the gimmicks and get to grips with this challenging approach to core training. Chris Mallac explains
From colourful Swiss balls to transversus abdominis work, core stability training has taken many shapes and forms over the past few years, depending on what is flavour of the month.
Most Swiss ball programmes, Pilates and other ‘core work’ provide a valuable benefit in physical preparation and injury management. They offer a lot of variety – and there are some things you can do on a Swiss ball or Pilates Reformer that you simply cannot do on any other apparatus.
Yet at times it seems as though personal trainers and athletics trainers are hell-bent on competing to invent the next latest and greatest core training fad. Many of these fail to appreciate fundamental principles of functional biomechanics and betray a poor understanding of how the lumbo-sacral spine and its supporting muscle system work.
This article, therefore, will introduce unfamiliar readers to some elementary ideas about the function of the lumbo-sacral spine and associated muscle systems, in particular the ‘myofascial slings’.
The concept of myofascial slings comes out the work done by Andry Vleeming and others on sacro-iliac joint (SIJ) stability. Contrary to what old rheumatologists will tell you, the SIJ does need to move during normal daily activities such as walking and running (see Lavignolle et al 1983).
Movement in the SIJ and sym-physis pubis is made possible by the fibrocartaligenous structure of these joints. It is both necessary and desirable that they move, so that they can act as shock absorbers between the lower limbs and spine, and to act as a proprioceptive feedback mechanism for coordinated movement and control between trunk and lower limbs.
As the SIJ is capable of some movement, this must be controlled for effective force transfer to take place between trunk and lower limbs. As the term ‘sling’ suggests, the muscle system is able to provide a dynamic way of stabilising the sacro-iliac joint through ‘force closure’.
The concept of force closure relates to the ability of a muscle system, through its attachment into connective tissue (ligaments and fascia), to compress two joint surfaces together and provide stability.
This is in contrast to ‘form closure’, in which the combination of joint structures (eg congruency or architecture) and related ligaments provide passive joint stability. To the therapist and trainer, ‘force closure’ is of greater interest because we can influence this through exercise and retraining.
The ‘slings’ that provide force closure in the pelvic girdle include the posterior oblique sling, the anterior oblique sling and the posterior longitudinal sling. These are made up as follows:
Posterior oblique sling: consists of the superficial fibres of the latissimus dorsi blending with the superficial fibres of the contralateral gluteus maximus through the posterior layer of the thoraco-lumbar fascia. The superficial gluteus maximus then blends with the superficial fascia lata of the thigh, in particular the superficial iliotibial band (ITB). This sling system runs at a right angle to the joint plane of the SIJ and in effect will cause closure of the joint when the latissimus and contralateral gluteus maximus contract. Furthermore, the gluteus maximus and thoracolumbar fascia have investments into the sacrotuberous ligament. Tension in this ligament will also cause closure of the SIJ.
Anterior oblique sling: consists of the external oblique, internal oblique and the transversus abdominis via the rectus sheath, blending with the contralateral adductor muscles via the adductor-abdominal fascia. This will cause force closure of the symphysis pubis when contracted.
Posterior longitudinal sling: consists of the deep multifidus attaching to the sacrum with the deep layer of the thoracolumbar fascia, blending with the long dorsal sacroiliac joint ligament and continuing on into the sacrotuberous ligament. In a proportion of the population, the sacrotuberous ligament extends on to the biceps femoris muscle. This causes compression of the L5/S1 joint and compression of the SIJ.
Key biomechanical training principles for the SIJ
- Keep the compression load vertical: as most athletic endeavours and functional daily activities are done upright, most of the ‘core’ training work should also be done upright. When vertical, it is necessary that loading be taken through the lower limbs and not the ischial tuberosity (as occurs when sitting). Ground reaction force when standing is transferred up the femur, into the acetabulum and the pelvic bones. This is met by the downward force of gravity acting on the trunk. This allows the natural ‘form closure’ mechanism of the SIJ when standing, as the sacrum sits into the corresponding surface of the ilium nicely in this position. Furthermore, the lumbar spine intervertebral discs prefer the compression force that standing provides, rather than shear force or tensile force. Most damaging shear force occurs when the vertebrae slide against each other and shear the adjoining intervertebral disc – as happens when the body is horizontal (the position used for many Swiss ball exercises). Tensile force occurs when the lumbar spine is flexed or extended.
- Keep the spine in neutral. The most common way to damage intervertebral discs is to have the spine flexed, as you do when bent over. In this position the pressure inside the disc increases significantly; with added compression, this position can cause discs to herniate. So it is important to keep the spine away from full flexion and extension positions, to avoid repeated microtrauma to discs, vertebrae and ligaments.
- Maintain rectus abdominis in isometric contraction: many elite athletic endeavours require that the rectus abdominals work isometrically. This allows the rectus to provide a stable anchor for the powerful oblique muscles to generate force. The rectus anchors the obliques via lateral tendons and this design allows force to be transferred laterally to the oblique muscles.
Training the myofascial slings
With close attention to good form, the simple twisting exercise in the diagram above is a good way of training the myofascial slings.
The key principles apply as follows:
- The exercise is performed standing up. As mentioned above, most sporting endeavours (except swimming and boat sports) are done upright, and training interventions should also be done this way to allow the natural ground reaction force and spinal compression mechanisms to work.
- There is slight knee and hip flexion. This will pre-tense the gluteus maximus and quadriceps. This is necessary to activate the tension mechanisms in these muscles in order to stabilise the distal element of the posterior oblique sling. The close relationship of quadriceps to the fascia lata of the thigh allows tension to develop in the superficial ITB.
- There is slight forward lean with anterior pelvic tilt. This activates the deep multifidus, a component of the posterior longitudinal sling. Flexion of the hip in the form of partial squat also activates the hamstring muscles, another part of the posterior longitudinal sling.
- There is trunk rotation against resistance. This activates the oblique muscles, part of the anterior oblique sling. The rectus must be isometrically contracted to allow the lateral bands of the rectus sheath to provide a stable base for the obliques to work from. It is also important that the participant understands how to activate the transversus abdominis in the form of a hollowing action, to allow pre-tension in the thoracolumbar fascia.
- The broomstick sits on the shoulders. Pulling the broomstick into the shoulders allows isometric latissimus dorsi contraction. A stable closed chain system is then created for the posterior oblique sling to work effectively.
How to perform the exercise
This exercise was originally developed at the Australian Institute of Sport in Canberra. The diagram and points i to v above will guide you on correct form. Tape or otherwise fix the resistance bands firmly to the broomstick.
As a yardstick, an appropriate level of resistance (band strength and length) should allow the client to perform 3 sets x 10 reps without great difficulty. Progress from there.
As a therapist, follow a good demonstration with good instruction. Verbalise the following points and cues:
- Keep quadriceps and glutes tight.
- Keep transversus hollow and tense rectus abdominis.
- Don’t rotate the pelvis, just the trunk. If the athlete has trouble dissociating pelvis and trunk rotation, have them perch their buttocks on the back of the chair, which takes about 25% of their body weight through the ischial tuberosities. This will give them feedback and position awareness so they can learn to maintain a stable pelvic position.
- Maintain a slight arch in the lumbar spine.
- Keep looking straight ahead, do not allow the head to turn with trunk rotation.
- Keep broomstick firm on shoulders in order to keep latissimus dorsi activated.
Note: one full repetition of this exercise involves rotating from x degrees backward trunk rotation to x degree forward trunk rotation, and then returning to the backward start point.
- Use a single band.
- Move through a small range of rotation 10 degrees to 10 degrees each direction (total arc of 20 degrees).
- Perform three sets of 10 reps each direction (band at left, then band at right).
- Use two bands, one either side of the broomstick.
- Rotate through 20 degrees to 20 degrees.
- Perform three sets of 10 reps in each direction.
- Can double up number of bands (or more, and/or use tougher bands etc), depending on the athlete’s available rotation strength
- extend range of rotation up to 45 degrees to 45 degrees.
- Perform three sets of 10 reps in each direction.
- Place one foot on a step to increase the range of hip flexion. This is particularly effective for sports requiring stability in positions of hip flexion, eg rowing and cycling.
- Decrease the width of the base of support by adopting a lunge stride position.
Myofascial slings: further reading
- Lavignolle B, Vital J M, Senegas J et al (1983): An approach to the functional anatomy of the sacroiliac joints in vivo. Anatomica Clinica 5: 169-176.
- Richardson C A, Jull G A (1995): Muscle control-pain control. What exercise should you prescribe? Manual Therapy 1: 2-10.
- Pool-Goudzwaard A L, Vleeming A, Stoeckart R, Snijders C J and Mens J M A (1998): Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to ‘a-specific’ low back pain. Manual Therapy 3(1): 12-20.
- Vleeming A, Stoeckart R, Volkers A C W, Snijders C A (1990a): Relation between form and function in the sacroiliac joint. Part 1: Clinical anatomical concepts. Spine 15(2): 130-132.
- Vleeming A, Volkers A C W, Snijders C A Stoeckart R (1990b): Relation between form and function in the sacroiliac joint. Part 2: Biomechanical concepts. Spine 15(2): 133-136.