THE last thing on your mind when you're about to break through to a new level of Tomb Raider is improving your posture or stopping for a break. Yet children who spend hours surfing the net or sitting hunched over games consoles run a high risk of developing repetitive strain injuries (RSI).

The painful condition is well known among adults, and now the popularity of games terminals, computers (especially laptops) and text messaging is putting young people at risk.

Mark Bender, believes that the addictive nature of computer games makes them doubly hazardous: "Children spend hours in an unnatural position, while carrying out habitual repetitive micro-movements with their hands - punching the keys or battling with tiny consoles."

The condition, also known as work-related upper limb disorder, causes a range of symptoms. Common complaints include tingling, pins and needles, numbness, weakness, loss of movement, muscle spasm, shooting pains and pain between the shoulder blades.

Regular breaks, time limits, stretching and exercise all help, but motivating children to change their behaviour is tough. "Few children want to leave the middle of a gripping computer game to run up and down the stairs or stretch," says Bender.

Children's spines are also more vulnerable to RSI as a result of doing less sport and sitting at desks that are too small for them. The average size of a pupil has grown significantly over the past 30 years but few schools have invested in bigger chairs and desks. Less locker space and more homework also oblige children to lug around heavy books, while some schools ban rucksacks - the safest way to carry heavy books.

"Children are still developing their bone structure and muscle tension, so bad posture could cause debilitating pain for life," says Bender.