The importance of the achilles tendon to runners

Tendon stress while running
You may think that strong leg muscles are the most important factor in determining the speed of forward running propulsion.

Take a look at Christian Olsson, the Swedish triple jumper. His ability to translate speed on the runway to the jumps seems more likely to be due to fantastic elasticity in his tendons than massive strength from his fairly skinny legs. The secret may well lie in the elastic fibres contained within the tendon. After all, the kangaroo's secret is not extreme power coming from its muscles but rather relates to the elasticity of its tendons. Each time it lands, energy is absorbed in elastic fibres in the tendon and is then returned very efficiently, almost like a spring uncoiling.

It is now thought that the calf muscles are not very active in the push-off phase of the human running action. They seem to work hardest when the foot first makes contact with the ground. The calf muscles and the achilles tendons then act mainly as a sort of shock absorber to control the impact with the ground. If the achilles is not strong enough or the impact is too great damage will occur.

For overpronator runners, it may be that the direction in which the tendon moves with each step is the critical factor; the tendon may be moving in a direction which puts too much demand on an otherwise reasonably strong tendon.

If the tendon is not healthy, the energy absorbed from the impact will not all be returned to help with forward motion. Some of the force of the impact will then produce further stresses on the tendon and small tears and areas of damage will accumulate.

What types of running injuries can occur?
Until fairly recently, most injuries to the achilles tendon were diagnosed as tendonitis. The "-itis" is medical shorthand for inflammation. Treatment would then focus on periods of rest and anti-inflammatory drugs. Sometimes steroid injections were given alongside the tendon in an attempt to soothe the inflammation.

As inflammation needs time to develop after the stressful activity has occurred, typically the pain will often not be felt for several hours after the activity, classically on getting up the following morning. If inflammation is the problem, a few days rest will settle symptoms but the pain is likely to recur if the training is not modified.

Achilles tendon injuries are more usually a form of tendonosis, with inflammation playing a relatively minor role. Tendonosis is a rather vague term which basically just means an unhealthy tendon. As a result of an imbalance between the strength of the tendon and the forces applied to it, small areas of damage appear within the tendon. The problem is that the achilles generally doesn't repair itself well.

This is even more of a problem in older runners. Depending on the severity of the damage, the pain will come on at different points during a run. It may actually settle down after five or ten minutes, only to gradually worsen towards the end of a run. The tendon will be sore and tender immediately after a training session (unlike the situation with the inflammation associated with tendonitis). It will also feel stiff and sore the next morning.

Partial rupture and complete ruptures of the tendon usually occur in tendons already severely damaged by the degeneration of tendonosis. Pain will appear suddenly, probably when the tendon is put under extra strain, such as beginning a sprint, running up hill or sudden change in direction. If the tendon is completely ruptured it may feel as though you have been struck on the back of the leg. Walking will be difficult or impossible. You may even hear a crack. If you think there is any chance that the tendon has completely ruptured you should seek emergency medical attention.

Treatment for achilles running injuries
Do you need to stop running? It is probably advisable to avoid running for at least one week after the symptoms first develop. After that, advice would depend on the grade of injury. In his book Lore of Running, Dr Tim Noakes describes four grades of injury:

• Grade 1 would be discomfort in the tendon first thing in the morning,
• Grade 2 would be pain on running but not affecting performance,
• Grade 3 pain affecting performance
• Grade 4 running is impossible.

Whatever the grade, before returning to training, correct any of the potential causes that you can. This may be the time to invest in a new pair of running shoes. Make sure that the calf muscles are not tight. For Grade 1, after one week's rest, it is probably not necessary to modify training too much. In Grade 2, it will be necessary to cut back on speed and hill work and possibly also mileage. In Grade 3, any running should be restricted to short jogs and cross-training is much preferred. For Grade 4, clearly no running should be attempted.

For all grades, eccentric exercises of the calf muscles and achilles tendon should be carried out. It is possible, over time, to strengthen the achilles tendon and, with healing, the elasticity will return. This will improve running ability and provide greater protection against injury in the future.

Why is the achilles tendon prone to running injury?
Achilles problems are often experienced after a relatively sudden change in the type of run training. More often this is when the quality is stepped up as in hill or speed training but occasionally it can be related to an increase in volume. Contributing factors include tight calf muscles, overpronation, stiff-soled shoes, shoes with flatter heels than normal and stiff ankle joints. Older tendons are also more prone to damage.

Ankle strains during running
Although running cross-country and on trails gives the muscles and tendons some protection from impact forces, the uneven ground requires the ligaments around the ankle to work harder. If the ligaments are not up to the job or too much is asked of them (by going over on the ankle) the ligaments will tear. Occasionally the damage is so great that the stability of the ankle is immediately affected and urgent treatment will be required. More often a few fibres in the ligaments on the outside of the ankle will tear and bruising and swelling will accompany the pain.

Immediate treatment is the usual; rest, ice, compression (with a crepe bandage or Tubigrip) and elevation. Until it is possible to walk without a limp, no attempt should be made to run. An ankle support may enable a slightly earlier return to training. Make sure that the ankle isn't allowed to stiffen. As soon as pain permits, move the ankle joint through a full range of motion.

After one episode of ankle strain the likelihood of further injury is increased. Contrary to popular myth, this is usually not due to a reduction in mechanical strength but is the result of a reduction in the body's ability to sense what position the foot is in, allowing muscles to make quick adjustments to take account of uneven surfaces.

This is because sensory nerve endings are contained within the ligaments and are damaged at the time of the original injury. To restore things to normal, exercises on a wobble board will help to restore a normal range of movement and also retrain the ligaments in their ability to sense the position of the foot.

There is usually a good reason why a specific injury has occurred at a particular time. If a period of rest is required, do what you can to prepare muscles, tendons and ligaments for future challenges. Injuries will recur if the causes have not been attended to.