Sport is increasingly popular as we have more leisure time and we are encouraged to be more active. Obesity is increasing and becoming a problem in all groups of people, especially in children. These two pressures are increasing our levels of participation in sport.

However, sport is not a completely positive pursuit. Injury, even long term disability, is a distinct possibility in many sports, and the risks of this kind of problem are not fully recognised.

Everywhere we are encouraged to exercise. When we are young we participate in sports at school and college, and when we are older it is suggested we exercise for our health, our hearts, our weight and our joints. It's pretty persuasive, isn't it? Even if we don't buy in to the whole message and take part we are aware of the pressure. Is this pressure a wholly good thing?

Young people play sport for fun, not for their health! When we are young we don't need to play sport for our health, because unless we are unlucky we are already healthy. Young people play hard and put large forces through their limbs and joints, risking injury in their competitive efforts. This can have long term consequences.

Older people don't participate in sport and exercise as much as younger people, but have more need to exercise. Sensible exercising in the years from fifty onwards can give benefits in terms of life expectancy and ability to function in life. At this age we are likely to be more moderate in the level of effort and forces involved, so are at lower risk of injury.

If we look at it logically, young people don't need to exercise (and do, hard) and older people do need to exercise (and don't). There's a interesting paradox! We need to look at this unquestioning acceptance of exercise as a good thing, as we hear very little of the personal and financial consequences of going for it.

Heavy exercise (high level sport, military training) is associated with a significant level of joint and other injuries. Many of these problems get worse over time and cause pain and disability. People in their forties and fifties may need joint replacement due to the arthritic changes which have developed since the initial injury. However, We can take some precautions to avoid problems later.

The ten tips for success in sports

1. Very young people should not put extreme forces on their spines and joints. Early gymnastics with large ranges of movement may give problems later.

2. If you are hypermobile (very bendy or "double jointed"), think very carefully about engaging in contact sports. Your joints are more vulnerable to injury and your muscles less able to control their movements to keep them safe from damage. I know someone whose joints are so lax that dancing is a risky activity!

3. Choose an activity to suit your physical type. Impact sports may not suit a high body weight, and a poorly coordinated person might not choose a complex contact sport. High level sport is not for everyone, no matter how much they want to participate.

4. If you get injured, get a proper diagnosis from a qualified person and follow the treatment plan. Do not be tempted to go back to the activity until you are completely recovered and have regained your fitness. Otherwise re-injury is likely.

5. If you have a serious (or repeated) injury to your spine or one of your joints, consider giving up the activity responsible and taking up some other, more appropriate, pursuit.

6. Take the advice of a competent physical therapist if your problem persists.

7. Moderate level exercise, such as brisk walking, can give you all the health benefits without the injury risks of more extreme sports.

8. Consider whether or not to encourage children strongly to be competitive in sports where they can get injured.

9. Don't just start a new sport straight off, work up your fitness and participation until your physical condition and skill are good enough to avoid injury. Be particularly aware of this at the times of the year when sports and other activities may start and you are least used to them.

10. Remember that fitness is very specific to the sport you are used to. Don't expect your fitness to transfer to a very different activity, or you may get muscle soreness or injury. For every new activity, you need to start again with your fitness.

Jonathan Blood Smyth is author of Secrets of Pacing and a Superintendent Physiotherapist in an NHS Hospital in the South-West of the UK. With over 15 years experience of managing orthopaedic conditions and looking after joint replacements, he now specializes in the management of chronic pain conditions. For more information on these and other subjects see The Physiotherapy Site.