Cologne, Germany - Sport is a healthy leisure pursuit provided the activity does not put an undue strain on muscles and joints.

Children are particularly prone to such hazards and if certain guidelines are not observed, playing sports can create undue stress and pain.

Parents, trainers and teachers should be aware that the sporting strengths and weaknesses of children are linked to phases in their physical development.

Ulrich Fegeler of the Cologne-based Federation of Child and Youth Paediatricians (BVKJ) explains why: "During puberty, boys gain more muscle mass but physical resilience is actually reduced since their bones grow faster than the muscle tissue."

Since their muscular systems are under-developed, weight-training with heavy loads or a high number of repetition is not suitable. Fegeler recommends sports which enhance stamina and motoric functions.

From their early years, children should be encouraged to improve coordination by running, jumping and through participation in ball sports and swimming.

There is nothing wrong with pre-school children taking part in such activities as ice-skating, rollerblading or skiing. Between the ages of seven and 10 years, children should aim to further hone their coordination skills.

At this age, their sense of balance has matured sufficiently and they are able to quickly master more sophisticated exercises. Ball games and gymnastics are ideal for this phase.

"The main risk of injury occurs through sudden muscle tension or jerking movements which can too much strain on a muscle - so even for young people, a stretching routine beforehand and a cool-down period afterwards are essential parts of any workout," said Fegeler.

The pace of training should be moderate too, especially for those unused to such exertion of suffering from overweight. A child or teenager who plays between 10 and 20 hours of tennis a week may already be overdoing it.

Parents should therefore consult a doctor before allowing their offspring to take part in regular sporting tournaments or competitions. (dpa)