Young people who exercise regularly may perform better in school, a new study suggests.

Scottish researchers looked at almost 5,000 children who were taking part in a long-term health study.

The children's activity levels were assessed at the age of 11, using a device known as an accelerometer, which is worn on an elasticated belt. It revealed that boys were getting an average 29 minutes of moderate to vigorous exercise per day, while girls were getting 18 minutes.

Both of these figures are significantly below the recommended 60 minutes of exercise per day that children are supposed to get.

Meanwhile, the children's academic performance in English, maths and science was also assessed at the ages of 11, 13 and 15/16.

Factors that can influence academic achievement, such as birth weight, the mother's smoking status during pregnancy and socioeconomic status, were taken into account.

The study found that at the age of 11, children performed better academically in all three subjects if they undertook more exercise. In particular, physical activity appeared to benefit girls' performance in science.

At the age of 13, academic performance still appeared to be linked to the amount of exercise the young people had undertaken at the age of 11.

And by the age of 15/16, academic performance in school exams also appeared to be linked to exercise.

For every additional 17 minutes of activity per day at the age of 11 among boys, and 12 minutes for girls, there appeared to be an increase in academic performance at the age of 15/16.

Again, the biggest benefit was seen in girls' science results.

"This is an important finding, especially in light of the current European Commission policy aimed at increasing the number of females in science subjects," the researchers said.

They speculated what impact exercise might have on academic performance if children got the full 60 minutes of daily exercise that they are supposed to.

"If moderate to vigorous physical activity does influence academic attainment this has implications for public health and education policy by providing schools and parents with a potentially important stake in meaningful and sustained increases in physical activity," the researchers concluded.

Details of these findings are published in the British Journal of Sports Medicine.