Health: Warning: exercise can damage your health

People starting fitness programmes often think they can do more than they should. By Roger Dobson

GETTING FIT can seriously damage your health. Exercise may be all very well for keeping the heart and lungs in shape, but other parts of the body are losing out in the sprint to get fit.

Backs and necks are getting strained, knees damaged, ankles twisted and bones cracked by the stresses and strains of running and jogging and myriad other activities that have become popular over the last 20 years in the fight against flab.

Participants also risk getting a variety of specific problems including jogger's nephritis, runner's knee, golfer's groin, parachutist's ankle, runner's claw toe, and thrower's elbow. And even worse, there are the diseases waiting to be caught from fellow enthusiasts, from conjunctivitis to legionnella. New research on the effects of exercise has found that there are hidden dangers in having too much of it, and sports medicine specialists now want the emphasis to be on quality rather than quantity.

A major problem only now being recognised is that many people embark on fitness programmes with an over-optimistic enthusiasm and assume the body is far fitter than it really is.

"If the Government is propagating healthy exercise for everyone, the message must be taken in the context that some people will take health advice to an extreme," says Professor Michael Horton, head of the bone centre at University College, London, and the organiser of a conference on the impact of exercise on the skeleton. While the density and strength of bones is boosted by exercise, too much of it can lead to a weaker skeleton as people become older. Women are particularly at risk: evidence from the USA shows that as many as 70 per cent of young women students who took part in college athletics had irregular menstrual cycles caused by exercise and poor diet and as a result were building up problems of osteoporosis in later life.

Bones grow and adapt to pressure by increasing the strength in those areas where it is needed. Football players have a very dense ankle structure and leg bones as a consequence both of running and of impact.

The danger of side effects from too much exercise is not the only problem facing those who want to get fit. There are risks associated with exercising while the skeleton is unfit and unprepared, and there is also the problem of choosing the right exercise.

"Swimming can increase muscle mass and help with the respiratory system, but it has no effect on the skeleton. Squash on the other hand is good because the rapid changes of movement increase bone mass. Activities with high impact and big changes in movement are best for the skeleton. Every time we put a foot on the floor the physical effect is sensed by the skeleton and it will adapt," says Professor Horton.

"One of the main problems is that if you take someone who is sedentary and put them in a training regime, then a substantial number may be at risk of injuries like stress fractures because of their immature skeleton. The message is that exercise is good for you, but your initial health has to be taken into consideration and you need to be aware that at extremes it can cause damage, particularly when taken without any preparation."

Prof John Davies, professor of sports medicine and medical adviser to the Welsh Rugby Union, says that 90 per cent of sports injuries involve damage to soft tissue, including sprains and strains. "We see a lot of pulled muscles and stress fractures and a lot of it is down to poor technique and people going at it too hard without any graduated regime," he says.

"Choosing the right activity is important. Some people, for instance, are built for running and others are not. There are alternatives to running and there is now evidence that power walking is as beneficial but without the jarring effects."

Over time, these jarring effects can have a serious impact on the cartilage of the knee leading to arthritis, and urban joggers running on hard surfaces are thought to be most at risk. Apart from the risk of trauma and long- term bone problems, there is also the danger of picking up an infection from other enthusiasts. These infections are known collectively as the changing-room syndrome.

"In the changing room people are in close proximity to each other in a crowded, moist atmosphere, and it lends itself to the transmission of a whole range of respiratory infections - sore throats, colds, fungal infections, verrucae and so on," says Prof Greg McLatchie, professor of sports medicine at Sunderland University.

And his research shows that the most unlikely places can be sources of infection. After several swimmers and curlers at a Scottish leisure complex went down with a form of legionellosis, investigators, eventually found that the airborne infection had travelled all the way along the pipes and vents of the ventilation system from a contaminated Jacuzzi.