Back pain is the UK's number one illness. It is the primary reason for people taking time off work, and the charity BackCare believes 180m working days are lost in the UK each year as a result of back problems.

Four out of five adults experience back pain, and on any given day there are a staggering 2.5 million people suffering. Runners are at increased risk because of the repetitive nature of the sport. So, to make sure you don't become one of the statistics, arm yourself with this advice from some of the UK's leading back experts. It will help you race and train without suffering.

Your back comprises 33 small bones, called vertebrae, and has built-in shock absorbers, called discs. The discs sit between the vertebrae and are made of a soft jelly-like substance held inside a tough, elastic outer casing. The lowest part of the back, the lumbar region, is the most vulnerable, because it has the most work to do and is also flexed, twisted and bent more than any other part of the spine.

Around 70 per cent of all lower back pain is idiopathic in nature, which means it originates elsewhere in the body's multi-segmented system. The lower part of this system is called the locomotor unit and includes the pelvis. It carries the upper part of the body, which is called the passenger unit and includes the spine, upper body, arms and head. These two units meet in the lower lumbar spine.

Most injuries that are referred to as "simple back pain" are caused by strains and sprains. In our working lives, as well as our running lives, we can expose our backs to minor damage from poor posture, poor abdominal strength, too much bending forward or backward, repeated quick or strenuous muscle contractions, tightness in the gluteus and hamstring muscles and tight connective tissue in the lower back, all of which lead to over-use injuries.

Understanding your back and how it affects your running is key to avoiding over-use injuries. "Because runners hold a specific form, the body ends up getting very little variety. Weakness and imbalance can set in," say Jim and Phil Wharton in The Whartons' Back Book. This can lead to injury: "Runners hold the record for overuse injuries among athletes in all fields - a massive 70 per cent. Of all runners, 37 to 56 per cent get hurt every year," they add.

One of the key reasons for back injuries among runners is excessive training on hard surfaces, so try to avoid always running on roads or pavements. On these hard surfaces, any misalignment in your musculoskeletal system will be absorbed higher up in the body, creating instability in the pelvis and spine.

Wearing the right running shoes will help you to avoid injury, especially if you have low foot arches. Overpronation (excessive rolling in) of the feet leads to exaggerated internal rotation of the shin, which causes excessive internal rotation of the thigh. The result is pressure on the hip joint, which tilts the pelvis forward. "This increases the angle where the spine joins the pelvis and is a very common cause of lower back pain," says Clifton Bradeley, an authority on back care for runners and the Clinical Specialist to Sub-4 Ltd. This scenario is commonly coupled with any number of other excessive pronation injuries such as Achilles tendonitis; plantar fasciitis; runner's knee; shin splints and iliotibial band syndrome.

You're also at risk from back pain if you have one leg shorter than the other. This can be rectified with a heel raise placed on an orthotic insole, which fits inside the shoes. Leg length discrepancies can be responsible for a range of sports injuries including sacroiliitis, sciatica, greater trochanteric bursitis, achilles tendonitis, plantar fasciitis, knee pain, shin splints and piriformis syndrome. A podiatrist, physiotherapist, chiropractor or osteopath will be able to tell you if you have a leg length discrepancy by assessing you for both anatomical and functional differences.

Running places great demands on your body, but by listening to any aches or stiffness in your back, which may in turn be weakening other areas, you'll be able to identify problem areas. Address back pain with targeted stretching and strengthening, and follow the advice to injury-proof your back (see panel), and you'll be able to return to your training stronger and more flexible than before.