Core stability training programme

Core Stability Training: This exercise programme will strengthen your trunk muscles and thus help avoid back problems

Strengthening the back extensor muscles is a useful preventive approach for low-back pain. However, the current vogue in physiotherapy and fitness training is to focus on what is known as 'core stability' training, which specifically targets the smaller and deeper lumbar spine and trunk muscles. 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. This article will review the theory and research that underlies core stability training and suggest a simple exercise progression to enhance this function.

Hodges and Richardson (1) have described the lumbar spine area as 'inherently unstable'. In practical terms, this means the lumbar spine relies for stability on the muscles that actively support the area. This 'active' support comes from four mechanisms; tension from theracolumbar fascia; intra-abdominal pressure; the paraspinal muscles; and the deep lumbar extensors (2).
The theracolumbar fascia (TLF) can provide a tensile support to the lumbar spine via deep-trunk muscle activity. The Transversus Abdominis (TA) and the Internal Oblique (IO) muscles both attach to the TLF. This fascia 'wraps' around the spine, connecting the deep trunk muscles to it. When the TA contracts it increases the tension in TLF which, in turn, transmits a compressive force to the lumbar spine, enhancing its stability. In addition the increased tension of the TLF compresses the Erector Spinae (ES) and Multifidus (MF) muscles, encouraging these to contract and resist spine flexion forces.

The intra-abdominal pressure mechanism (IAP) can provide a supportive effect for the whole lumbar area. A co-contraction of the pelvic floor, TA, IO and low back muscles increases the IAP which, in turn, exerts a tensile force on the rectus sheath. This sheath encloses the Rectus Abdominus (RA) muscle and attaches to the IO and TA, surrounding the abdomen. The tension of the rectus sheath increases the pressure within the abdomen like a pressurised balloon. This supportive 'bag of air' reduces the compression and shear forces acting on the spine. Research shows that IAP increases before and during weightlifting exercises(3) and also during running(2), lending credence to the idea that it plays a crucial role in lumbar stability.

Research also demonstrates the significance of the paraspinal and deep lumbar muscles as important stabilisers. It is likely that these muscles act with a static contraction to resist any lumbar extension and rotational forces. The paraspinal muscles - Interspinalas and Intertransversarii - provide an individual stabilising effect on their adjacent vertebrae, acting in a similar way to ligaments (4). The deep lumbar muscle - multifidus (MF) - has been shown to be active throughout a full range of motion of the lumbar spine and during movements of the lower and upper limbs (5).

From this brief explanation of the anatomy and research into the muscles of the lumbar trunk area, it is clear that the deep-trunk muscles - TA, MF, IO, paraspinal, pelvic floor - are key to the active support of the lumbar spine. The co-contraction of these muscles produces forces via the TFL and IAP mechanism which stabilise the lumbar spine, and the paraspinal and MF muscles act directly to resist the forces acting on the lumbar spine.

Further study showed that it is not just the recruitment of these deep-trunk muscles but how they are recruited that is important. Hodges and Richardson showed that the co-contraction of the TA and MF muscles occurred prior to any movement of the limbs. This suggests that these muscles anticipate dynamic forces which may act on the lumbar spine and stabilise the area prior to any movement. Hodges and Richardson also showed that the timing of coordination of these muscles was very significant, and that back injury patients were unable to recruit their TA and MF muscles early enough to stabilise the spine prior to movement. The onset of the contraction before any force can act on the lumbar spine is essential for these muscles to act as stabilisers. Furthermore Hides et al (5) found that the MF muscle showed poor recruitment in back injury patients, again showing how the recruitment of these deep trunk muscles is very important.

Interestingly, as early as the 1920s Joseph Pilates talked about developing a 'girdle of strength' by learning to recruit the deep-trunk muscles. Even without a complete knowledge of anatomy and the benefits of the latest muscle activity research, he was aware of the importance of these deep muscles and their supportive effects.

Having identified the key muscles and how they act, the next step is to establish how best to train them. As with any type of strength and conditioning training, the 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 use static, or isometric, contractions. Furthermore, they must act as stabilisers continuously during everyday activities as well as sport, and so require very good endurance of low-level forces. These muscles do not need to be very strong, but they must be correctly coordinated and capable of working continuously; in addition, they must hold the lumbar spine in the neutral position - 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 programme.

The basics...
Core stability training begins with learning to co-contract the TA and MF muscles effectively, as this is key to the lumbar-support mechanism. To do this you must perform the 'abdominal hollowing' technique with the spine in the neutral position, as follows:

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 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.

Sounds easy? Well maybe, but it is absolutely vital that you perform this abdominal hollowing exercise correctly; otherwise you will not recruit the TA and MF effectively. The following tips will help to ensure your practice is correct.

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;
brace your TA muscle too hard; just a gentle contraction is enough. Remember it's endurance not max strength you are trying to improve;
tilt your pelvis or flatten your back, as this means you have lost the neutral position you are trying to learn to stabilise;
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.

Do:
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, practise 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.

The next step...
Having learned to recruit the TA and MF muscles correctly in various positions, which can take anything from one session to one month or more, it is time to move onto simple core stability exercises. These may also involve the oblique muscles, other lumbar muscles and gluteals to assist the TA and MF in maintaining the lumbar spine in a stable neutral position. I have chosen two very useful examples, but there are many others included in Pilates lessons and used by trainers and physiotherapists that can be incorporated at this stage of core stability learning.

Lying leg-lift stabilisation
Lie on your back with your knees bent, ensuring your back is in neutral and placing your hands on your hips for biofeedback;
Breathe in and relax. Breathe out and, as you do so, perform the abdominal hollowing or zipping-up action;
Once you have established some TA tension, slowly slide your left leg out along the floor until it is straight, then slide it back. Your back should not have moved, and your pelvis should not have tilted as you performed this action. If your back or pelvis moved, you did not achieve the correct stability. Remember the coaching points above, and ensure you follow them, otherwise you will jeopardise the training;
n Repeat for the other side, 10 times each leg.

The waiter's bow
Stand up with good posture, knees soft, lumbar spine in neutral, head up and shoulders back and relaxed;
Breathe in and relax. Breathe out and, as you do so, perform the abdominal hollowing action;
Keeping the tension, slowly lean forward from the hips at an angle of 20û and stop, in a posture like a waiter's bow, keeping your back completely straight and long as you lean. Hold the lean position for 10 seconds - you will feel your TA and MF supporting you if you hold the correct position;
Keeping the tension and the alignment, slowly return to your start position. Repeat 10 times. Again, remember the coaching points above.

These exercises are two examples of how you can learn to keep the spine in neutral, using slow and controlled static contractions of the trunk stabiliser muscles. Technique is vital and the aim is to build up the time you are able to maintain good stability.

Getting functional...
The ultimate aim of core stability training is to ensure the deep-trunk muscles are working correctly to control the lumbar spine during dynamic movements, such as lifting a heavy box or running. Therefore it is important that once you have become proficient in the simple core exercises you should progress to achieving stability during more functional movements. I have chosen two examples.

The lunge
A classic exercise which, performed slowly and with care, can teach you a great deal about body awareness and core stability. Interestingly, it is used by Alexander Technique teachers to help establish better movement patterns.

Stand with feet hip-width apart in front of a mirror. Ensure your lumbar spine is in neutral and your back is tall with your shoulders back and head up;

Lunge forwards, bending your knee only half way down. Ensure that your front knee is in line with your toes and your back remains upright, with your lumbar spine in neutral and your hips level;
Push back up, initiating the movement by pushing down into the floor with your front foot. The force from your legs should bring you back up quickly and easily to your start position. Your back should have remained totally still and your hips level as you performed the push back.

Many people wrongly initiate the up movement by pulling their heads and shoulders back first; this extends the lumbar spine, losing the neutral position. Others have problems keeping their pelvis level while performing the lunge. You must learn to use your deep trunk and gluteal muscles to hold your lumbar spine in neutral and your pelvis level as you perform the movement up and down. The movement should come only from the leg muscles.

The press up
Another classic exercise which, more often than not, is performed with questionable core stability.

Start on all fours - even if this means it is easy for your upper body - in order to learn the correct technique. Your hands should be slightly further than shoulder-width apart and your shoulders and your head in front of your hands. Lift your hips so that there is a straight line from your knees through your pelvis and lower back, through your shoulders and all the way to your head. Ensure your lumbar spine is in neutral, using a mirror or a partner/trainer to help you. To maintain a neutral spine and a straight back during the exercise, the trunk muscles must provide active support;

n Slowly lower down, bending your arms all the way to the floor. Keep your head still, with your neck in line with your back;

n Push up, initiating the movement by pressing down into the floor with your hands. Your back should remain still and straight and your lumbar spine in neutral throughout.

Many people allow their lumbar spine to arch and sag downwards as they perform the press up; this is because they are not using their trunk stabilisers to support the body.

These two exercises, used in a non-traditional manner, enable you to learn core stability while performing dynamic movements. By reducing the resistance - ie doing only half lunges and knee press ups - you are able to focus on the trunk stabilisers and achieving perfect technique rather than working the major muscle groups. The whole essence of core stability training is quality of movement and relaxation. The more you practise, the easier it becomes until you can control your lumbar stability at all times, during complex as well as simple movements.

Raphael Brandon

References:
1. Spine, 21, 2640-2650
2. International Journal of Sports Medicine, 1(4), November 2000
3. Zatsiorski (1994). Science and practice of strength training. (1994). Human Kinetics: Champaign IL
4. Palastanga et al. (1994). Anatomy of human movement. Butterworth Heinemann: Oxford.
5. Physiotherapy, 36, 6-11.
6. Spine. 21, 2763-2769.

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