A study published today in the British Medical Journal (BMJ) found that 52.5% of seven-year-olds in Scotland were achieving the basic target of one hour of moderate to vigorous physical activity per day. This compared to 52% of children in Wales, 51% in England and 43% in Northern Ireland.
However, the findings also mean that almost half of seven-year-olds in the UK are sedentary for six to seven hours every day, with girls and children of Indian origin -together with youngsters in Northern Ireland - the least physically active on average.
The authors base their findings on a sample of almost 7000 primary school children who were all part of the Millennium Cohort Study, which is tracking the long-term health of around 19,000 children born in the UK between 2000 and 2002.
The duration and intensity of children's daily physical activity levels were captured for a full week between May 2008 and August 2009, using a gadget called an accelerometer, worn on an elasticated belt. The children only took this off when they bathed or went to bed.
UK guidelines on daily physical activity levels were revised in 2011. These recommend that children engage in moderate to vigorous physical activity for at least an hour every day, and that they spend less time sitting down, although no maximum has been specified for this.
A previous study of Scottish children found that 15% exercised for less than an hour a day, with almost one-third (31%) watching television or using computers and other devices for more than three hours a day.
The analysis showed that on average, across the entire sample, children managed 60 minutes of moderate to vigorous physical activity every day, and that they took an average of 10,299 steps.
But the accelerometer readings also showed that half of the children were sedentary for six or more hours every day, and that half of them did not reach the daily recommended exercise target.
Girls fared worse than boys, in terms of total physical activity, moderate to vigorous physical activity, and in the number of steps they took every day.
They were also more sedentary and less likely to meet their recommended daily exercise target than the boys. Just 38% of girls achieved this compared with almost two-thirds of the boys (63%).
Meanwhile, children of Indian ethnic origin spent the least time in moderate to vigorous exercise, and took the fewest steps each day. Only one in three children of Bangladeshi origin met the recommended daily exercise minimum.
Senior author Professor Carol Dezateux describes the gender differences in exercise levels as striking, and calls for policies to promote more exercise among girls, including dancing, playground activities, and ball games.
The authors refer back to the legacy of the London 2012 Olympic Games, which promised to inspire a generation to take part in sport.
They write: "The results of our study provide a useful baseline and strongly suggest that contemporary UK children are insufficiently active, implying that effort is needed to boost [physical activity] among young people to the level appropriate for good health."
This is likely to require population-wide interventions, they say, including policies to make it easier for children to walk to school, in a bid to increase physical activity and curb the amount of time they are sedentary.
They conclude: "Investing in this area is a vital component to deliver the Olympic legacy and improve the short and long-term health of our children."