The aim of core stability training is to effectively recruit the trunk musculature and then learn to control the position of the lumbar spine during dynamic movements.
The deep trunk muscles, Transversus Abdominis (TA), Multifidus (MF), Internal Oblique (IO), paraspinal and pelvic floor are key to the active support of the lumbar spine. The co-contraction of these muscles produce forces via the "theracolumbar fascia" (TLF) and the "intra-abdominal pressure" (IAP) mechanism which stabilise the lumbar spine. The paraspinal and MF muscles act directly to resist the forces acting on the lumbar spine.
Having identified the key muscles and how they act, the next step is to establish how best to train these muscles. As with any type of strength and conditioning training, the training protocol for improving the function of the deep-trunk muscles must be specific to the task required. This specificity of training must take into account the type of contraction, the muscle fibre type and the anatomical position required. By definition, the deep-trunk muscles act as "stabilisers" and are not involved in producing movements, but instead involve static, or isometric, contractions. Furthermore, they must act as stabilisers continuously throughout everyday activities as well as fitness and sport activities, and so require very good endurance of low-level forces. These muscles do not need to be very strong, but they must be correctly co-ordinated and capable of working continuously. In addition, we want these stabiliser muscles to act by holding the lumbar spine in the neutral position, which is the correct alignment of the pelvis that allows for the natural 'S' curve of the spine. These characteristics underpin the following deep-trunk muscle training program.
Core-stability training begins with learning to co-contract the TA and MF muscles effectively as this has been identified as key to the lumbar-support mechanism. To perform the TA and MF co-contraction, you must perform the "abdominal hollowing" technique with the spine in the neutral position.
To do this, use the following guidelines:
- Start by lying on your back with knees bent.
- Your lumbar spine should be neither arched up nor flattened against the floor, but aligned normally with a small gap between the floor and your back. This is the "neutral" lumbar position you should learn to achieve.
- Breathe in deeply and relax all your stomach muscles.
- Breathe out and, as you do so, draw your lower abdomen inwards as if your belly button is going back towards the floor. Pilates teachers describe this as "zipping up", as if you are fastening up a tight pair of jeans.
- Hold the contraction for 10 seconds and stay relaxed, allowing yourself to breathe in and out as you hold the tension in your lower stomach area.
- Repeat 5-10 times.
It is vital that you perform this abdominal hollowing exercise correctly otherwise you will not recruit the TA and MF effectively. Bear in mind the following points:
- Do not let the whole stomach tense up or your upper abdominals bulge outwards, as this means you have cheated by using the large Rectus Abdominus muscle (the six-pack) instead of TA
- Do not brace your TA muscle too hard; just a gentle contraction is enough. Remember it's endurance not max strength your are trying to improve
- Do not tilt your pelvis nor flatten your back, as this means you have lost the neutral position you are trying to learn to stabilise
- Do not hold your breath, as this means you are not relaxed. You must learn to breathe normally and maintain the co-contraction of TA and MF
- Use your fingers for biofeedback on either side of your lower abdomen to feel the tension in the TA muscle.
- Once you have mastered the abdominal hollowing lying on your back, practice it lying on your front, four-point kneeling, sitting and standing. In each position, get your lumbar spine into neutral before you perform the hollowing movement.
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