Vigorous exercise sessions aimed at increasing activity levels are "likely to prove counterproductive as children demonstrate resistance to regimented, compulsory exercise", they say.
Professor Neil Armstrong, head of the Children's Health and Exercise Research Centre, whose latest report on primary pupils' activity levels breaks new ground, told The TES Scotland: "Daily PE is fine so long as it means physical education and not physical exercise."
He suggested teachers should work on basic motor skills to allow children to taste success in sports at a later stage and recommended short periods of PE, which fitted into children's natural patterns of activity and shorter attention span. "We're trying to change lifestyle and to sustain activity into adult life," he said.
The study of 153 primary pupils, which monitored heart rate for days at a time, showed that few 5-11 year-olds were active enough for their own long-term health and fitness. It is the first time such young children have been so scientifically observed.
Professor Armstrong said primary children were as fit as they ever were but were storing up problems for later life by being the most sedentary generation. He pointed out there were now 25 per cent fewer children walking to school than 20 years ago.
His findings reveal over 50 per cent of girls and 36 per cent of boys never manage the equivalent of a brisk ten-minute walk a week. Sustained periods of moderate activity and 10 to 20 minute periods of vigorous activity are rarely seen in the age group. Professor Armstrong said he was "quite surprised" at the results.
The second key finding is that girls are more inactive than boys with the decline setting in very early in primary.
Boys' activity levels are relatively high throughout primary but taper off towards secondary.
Parents' influence on their children is said to be significant with boys receiving more encouragement to be physically active.
Professor Armstrong and his co-researcher, Joanne Welsman, argue the promotion of enjoyable experiences of physical activity should start early in primary and that curriculum content is more important than time.
They reiterate: "When the curriculum emphasises developing motor skills and co-operative rather than competitive activities, it has been shown to be very popular with children.
"Ensuring that children experience fun and success in the early years of physical education is likely to be critical to sustaining interest in physical activity."
Physical Activity Patterns of 5-11 Year Old Children, by Joanne Welsman and Neil Armstrong, is published by the Children's Health and Exercise Research Centre, University of Exeter EX1 2LU.