Scotland should not be patting itself on the back for increasing exercise among children, because there is no way of knowing how many are achieving the national target of an hour's physical activity every day.
This was claimed by John Beattie, the broadcaster and former Scotland rugby international, who chaired the physical activity task force that, in 2002, outlined an ambitious 20-year plan to improve the nation's health.
Earlier this month, a sportscotland report showed that physical activity in schools had leapt up, thanks to the Active Schools scheme, but Mr Beattie suggested it was too early to get excited.
A total of 350,000 activity sessions took place in schools which had Active Schools co-ordinators in 2005-06, in addition to timetabled PE. There were no national figures, however, to show how many children took part in 60 minutes' physical activity a day; the only evidence came from South Lanarkshire and Dumfries and Galloway, where 73 per cent of primary pupils and 48 per cent of secondary pupils achieved the target.
"I don't see massive change," said Mr Beattie. "I don't see that everyone's changed. I think that the Active Schools programme hasn't had a major impact on the general physical activity levels of the population.
"I haven't seen any data that tells me to what extent kids who were already active are just doing more activity sessions. It doesn't tell you how many people have gone from being inactive to being active."
Sportscotland said there were no national figures for the 60-minute target, as it would not be cost-effective to undertake such a survey, and because it would duplicate work done through the Scottish Health Survey every three to four years. It stressed instead that physical activity and sport sessions in schools had risen by 53 per cent at primary level, and 17 per cent overall, in the two years since Active Schools was launched with an annual pound;12 million from the Scottish Executive.
Stewart Harris, chief executive, said: "There are more opportunities than before to take part in a wide range of physical activities and sport, and the more detailed evidence from two local authorities is demonstrating that physical activity levels are increasing, particularly in primaries."
There is no shortage of teachers and education officials willing to provide anecdotal evidence of increased physical activity. Michael O'Neill, North Lanarkshire education director, said that the 23 Active Schools co-ordinators in his region had had an "enormous impact".
The council expects that, by August 2007, every pupil will be achieving two hours' physical activity at school each week, a year ahead of schedule for that national target. Mr O'Neill added, however, that teachers were restricted in attempts to encourage more physical activity because of the demands of the 5-14 curriculum.