Computers may have become a necessity for today's kids, but a study says that the machines are producing a "generation of weaklings" as children swap outdoor play for screen games and the Internet.

The study of 10-year-olds found that the number of sit-ups they could do dropped nearly 30 per cent between 1998 and 2008. And, while only one in 20 kids failed to hold their own weight hanging on wall bars in 1998, the number doubled to one in ten by 2008.

The Essex University study, based on a survey, also found that as kids followed fewer traditional activities, such as tree-climbing, their arm strength dropped 26 per cent - and their grip seven per cent, 'The Sun' reported.

Children's fitness expert Dr Gavin Sandercock, who led the study, was quoted as saying, "Typically, these activities boosted children's strength, making them able to lift and hold their own weight."