Both my children are into sport, especially competitive gymnastics, but recently my daughter's flexibility has decreased and she is now less flexible than her brother. She is worried this will continue. What can she do about it?

Contrary to popular conception, children aren't always more flexible than adults, and girls aren't always as flexible as boys. Decreases in flexibility during childhood and adolescence are a direct result of growth, and I suspect your daughter is experiencing a growth spurt. As bones grow, the muscles and tendons tighten across the joints. This reduces flexibility, and makes adolescents vulnerable to injury from any jarring action such as jumping or kicking, or from long-term overuse.

The first thing to do is to minimise the risk of injury during such periods of rapid growth. Reduce the intensity of her training sessions, especially with explosive movements such as tumbling and vaulting. Instead, place more emphasis on stretching - both static stretches, which are held for 10-30 seconds, and dynamic stretches, which stretch the muscle with controlled movement. Partner stretches, such as proprioceptive neuromuscular facilitation (PNF), which involves stretching, contracting and relaxing muscles, and then moving deeper into a stretch by using a prop or partner, are particularly effective for increasing flexibility and may be useful once the growth spurt has passed. While she may feel slightly frustrated, in this way she can maintain her flexibility and reduce her risk of injury.

· Joanna Hall is a fitness expert (joannahall.com). Send your exercise questions to Weekend, 119 Farringdon Road, London EC1R 3ER (weekend@theguardian.com).