The sporting spine – what all athletes should know about core strengthening

‘There are two types of people in this world- those who have back pain and those who are going to get back pain’! While this may be an exaggeration, research suggests that 80% of people will suffer with lower back pain at some time in their life(1). But as TJ Salih explains, sportsmen and women can reduce this risk with targeted core strengthening work

Anatomy of the healthy spine

The spine consists of 33 individual bones or vertebrae and 23 intervertebral discs. The spine is comprised of neck (cervical), thorax (thoracic) and lower (lumbar) bones (vertebrae). Each has a slightly different shape, which, when fitted together, form a lazy ‘S’ shaped curve. This curve is very important as it provides the optimum mechanical advantage, putting the least amount of stress and strain on the surrounding joints, ligaments and discs.

The vertebrae communicate with each other via small joints on either side (facet joints). These joints allow only small movements within adjacent vertebral bodies but when moved together allow large spinal movements (much like a child’s wooden snake toy). These joints are like other joints in the body only on a smaller scale; they have cartilage to absorb shock and lubricate like other joints.

The intervertebral discs sit between the vertebrae to separate them. Each disc is rather like a car tyre. The outer wall (annulus) is made up of thousands of layers with fibres that crisscross making it very strong. The middle (nucleus) is made up of a protein that is over 80% water, this means that it is very resilient to being compressed and thus is a good shock absorber.

Ligaments attach to the vertebrae at the front, back and sides of the spinal column to provide a strong, non-elastic support to the spine and allow muscles to make close attachments to the spine. These ligaments should be thought of in the same way that we think about ligaments in any other joint; ligaments of the spine can be sprained/strained just as those in the knee and other joints can. Prolonged stretch or awkward positions of the spine can precede strains, especially when core muscles are weak.

Muscles surround the spine and encase the trunk. These muscles serve to move the spine through its different functional positions – eg forwards, backwards and twisting – but they also have a stabilising effect. Deeper (core) muscles act as a girdle supporting the spine providing a stable platform to allow other high-level activities from the upper and lower limbs (kicking a ball or serving in tennis). This stabilising function is now believed to be of fundamental importance for a healthy spine.

In addition to providing us with mobility, the spine provides a safe encasement of the spinal cord. The spinal cord runs down the spinal canal, through the centre of the vertebrae. The peripheral nerves that supply all the muscles and skin of the body come from the spinal cord and these pass through gaps at each level of the vertebrae. The intervertebral discs are fundamental in allowing sufficient space for these nerves to exit.

Pain in the spine

Intervertebral disc problems are unique to the spine. A ‘prolapsed’ disc occurs when the ‘pulp’ or nucleus in the middle of the disc herniates out, potentially pressing onto a spinal nerve. Other terms used are ‘slipped’ disc or ‘ruptured’ disc. If the spinal nerve is being compressed, or if the canal that a nerve needs to exit the spinal column is being compromised, pain may be felt down the entire length of the nerve or just where the nerve ends. For example, irritation to the nerve at your elbow can produce pain in the little and ring finger. Certain spinal positions (bending forward and twisting), prolonged postures (sitting and being bent forwards) and poor spinal control (because of poor core muscle strength) all increase the chances of a potential disc prolapse.

Most cases of spinal pain will resolve within six weeks, during this time bed rest is to be avoided and normal activity should be maintained as pain allows(2). However, extreme movements and sustained postures should also be avoided because subsequent episodes of spinal pain are unfortunately common.

Core strengthening and spinal health

‘Core strengthening’ has become very topical recently in rehabilitation of the athlete. Core strengthening is basically about developing the muscular control required around the spine to maintain functional stability(3). Research has shown that core muscle stability training improves function and activity of people with spinal problems and reduces the reoccurrence of spinal pain(4-6). Moreover, the girdle or core muscles of the spine can become weak and uncoordinated after just one episode of spinal pain(7). This reduces the support around the spine and so further increases the risk of further episodes of spinal pain and injury.

Spinal problems among sportsmen are no different from those in the general population. Keeping fit and active reduces the risk of back pain; therefore athletes could expect to have a lower incidence than the general population. However, studies have shown that high volumes of training can put the spine under greater stress, and so incidence of injury is increased(8). One study on dancers indicated that the incidence of spinal pain was not linked to the average total hours of activity, until this exceeded 30 hours per week(9). Although these studies may show a minor trend with increased physical activity and increased pain incidence, the outcomes of treating athletes with spinal pain are reported to be good(10).

Some researchers have found that general exercise programmes can be just as effective at reducing pain as specific core exercises(11-13). However, these studies were not performed on athletes, but on ‘general populations’ with back pain, and so we can’t draw conclusions about the suitability of general exercise programmes for athletes with back pain.

Sports-specific spinal health

Although there’s a wealth of research on core exercises and pain reduction, research that relates specific core exercises to specific sports is scarce. However, there are some sports that warrant special recognition with regard to spinal health, because they carry specific risks or an increased incidence of spinal injury. We will briefly discuss a few of these with reference to particular ‘troublesome’ areas that need to be targeted with specific stretches.

Football

In football players, certain muscle groups have a tendency to become overdeveloped, leading to muscle imbalance. These include over-strong quadriceps, over-strong or shortened hamstrings, tight hip flexors, tight over-developed calves, over-strong rectus abdominis, and weak core muscles. Most footballers also favour one leg, leading to an imbalance between sides. The result can be poor trunk and pelvic stability with poor spinal flexibility. To combat this, sport-specific stretches should be performed to aid flexibility and core stability exercises should be performed to aid stability and to prevent injury reoccurrence(14). Useful specific stretches that a footballer can do include quadriceps, hamstring, hip flexor, calf and abdominal wall stretches. These specific stretches, in conjunction with core stability exercises (see later), can minimise the likelihood of injury and increase performance.

Rugby

Although it’s a generalisation, a large proportion of the rugby game is played in semi-crouching, forward-leaning position. This can lead to muscle imbalances of the neck and upper shoulders, tight hips flexors due to the constant forward-bending position, and too much specific extension (arching) of the lower back. Specific stretches for these areas, with core stability exercises, can benefit the rugby player immensely.

Rugby is also a sport that has a history of a relatively high frequency of spinal cord injuries and spinal fractures. Unfortunately, no amount of core work or stretching can prevent such injuries. However, during the 1970s and 1980s, researchers identified an increase in the frequency of spinal injuries among rugby union players in many countries(15,16). Subsequently, the Rugby Football Union implemented changes for school rugby relating to scrums, rucks and mauls, which became effective in the 1985/86 season on an international basis(17), leading, for example, to a 67% reduction in the number of scrum-engagement spinal injuries recorded in Australia(18).

Cricket

Cricketers can sometimes develop a stress fracture injury of the vertebra (spondylolysis). In this injury, either because of a developmental abnormality, or more often because of repeated stress on a small part of the spine, a small crack develops. This crack does not normally displace or move, and can often only be detected on a bone scan.

Fast bowlers are the particular group most affected by this condition(19,20) but it appears that the amount you bowl is not necessarily a precursor of pain(21). Australian researchers found that over a 10-year period, fast bowlers missed approximately 16% of playing time due to injury, while for other positions it was less than 5%(22). Given that the volume of bowling is not linked to the risk of spinal pain, the technique of bowling seems the most likely cause of injury.

Fast bowling in cricket requires the spine to act as a whip for the arm. The low back bends backwards as far as it can (hyperextension), together with rotation and sideways bending of the trunk. This puts stress on an area of the vertebra called the ‘pars interarticularis’, which is where stress fractures develop.

In the majority of cases, a period of rest will allow the fracture to heal. However, returning to the same technique at the same intensity often results in a reoccurrence of the problem. To prevent reoccurrences, the bowler’s technique needs to be modified. It tends to be the rotation of the spine that is problematic(23), so a ‘purer’ technique of front-faced or side-faced bowling is preferable. Getting professional coaching to prevent shoulder counter-rotation and to fully analyse foot and hip placement during bowling will minimise further episodes of spinal pain.

Flexibility is also vital for the cricketing spine, not only for the spine itself but also for the shoulder girdle as this area is heavily involved during a game of cricket. Stretches that involve the spine, scapulae and shoulder should be incorporated into the warm-up programme. Core stability exercises are also vital to create support around the spine and around the particular spinal segment involved in injury.

Rowing

Lower-back pain is a common problem in rowers, largely because of the prolonged overall flexion (spine bent forward) of the rower in the boat, along with the repetitive action of bending forward and backwards of the spine during the rowing action. These positions place the ligaments and discs under increased amount of strain (as the protective lazy ‘S’ is lost). Poor technique can also increase the risk of injury – usually the result of an asymmetrical technique – which also adds a rotational strain on to the spine. Weakness of the deep core muscles may further increase the risk of injury.

To prevent back pain, rowers need to ensure that they have the flexibility required for the rowing positions together with the core stability and strength needed to protect the spine. Muscle imbalances often include tight rectus abdominis muscles and poor core muscle stability. Anterior knee problems are also common (from the repetitive forces generated through the knee) as are those of the thoracic spine. Specific stretches that target these muscles and that open the anterior chest should be performed.

Conclusion

To conclude, while there are certain sports that require special consideration with regard to spinal health, all sportsmen and women can suffer from spinal pain and injuries. More studies looking at the effects of core stability exercises on injury reduction in specific sports are needed, but there are a number of simple core strengthening exercises that can and should be incorporated into specific sports training and rehabilitation programmes to offer protection of the spine and to provide athletes with a strong platform to allow them to execute their highly skilled actions.

TJ Salih is a chartered physiotherapist and worked for Tottenham Hotspur Football Club for two seasons, before establishing his own clinic, Back2Normal – www.back2normal.co.uk

References
1. Pain 2000; 84:95-103
2. Clinical Guidelines for the Management of Acute Low Back Pain Royal College of General Practitioners 1999
3. Arch Phys Med Rehabil 2004; 3 (Suppl 1): S86-92
4. Med Sci Sports Exerc 2004; 36(6):926-934
5. Curr Sports Med Rep 2004; 3(1):41-46
6. Curr Sports Med Rep 2004; 3(1):35-40
7. Spine 1996; 21(22):2640-2650
8. Br J Sports Med 2003; 37(3):263-266
9. Man Ther 2001; 6(4):213-220
10. Prim Care 2005; 32(1):201-229
11. Spine 2001; 26(8):897-908
12. Clin Biomech 2005; 20(5):474-482
13. Phys Ther 2005; 85(3):209-225
14. J Orth Sports Phys Ther 2004; 34(3):116-125
15. Sports Med 2002; 32:633-653
16. The Lancet (editorial) 1984; 1:1108
17. Sports Med 1988; 5:328-334
18. Paraplegia 1993; 31:759-763
19. J Sports Sci 2000; 18(12):983-991
20. Clin J Sport Med 2002; 12(2):107-112
21. Br J Sports Med 2004; 38(2):125-128
22. J Sci Med Sport 2006; June 10: (abstract)
23. Sports Biomech 2004; 3(2):263-284