Only a few cases have been reported in his Ealing practice so far, but Mr Irwin expects a lot more as users realise their discomfort is not going away. "In the next six months I expect to see a big rise in the number of people with RSIlike symptoms from using these gadgets," he said. "The condition can be extremely painful."
Mr Irwin said he is particularly worried about children using iPods for long periods, as their joints are still growing and extended usage could cause "problems they will not see until early adulthood". He called for Apple and other manufacturers of MP3 players to take RSI into account when designing devices.
Apple, which has sold over 27 million iPods worldwide, refused to comment on the warning, which is backed up by the views of some American experts.
"Handheld electronics may require prolonged grips, repetitive motion on small buttons and awkward wrist movements. This combination can lead to hand, wrist and arm ailments such as carpal tunnel syndrome and tendinitis," said Donna Stanton of the US Society of Hand Therapists.