University of Wollongong physical activity expert Professor Tony Okely will join Federal Sports Minister Bridget McKenzie in Canberra this morning to launch the Australian 24-Hour Movement Guidelines for Children and Young People.

Prof Okely and his team helped develop the guidelines, which for the first time look at the connection between physical activity, screen time and sleep for five to 17-year-olds over a 24-hour period.

"It acknowledges that the whole day matters, and that physical activity, sedentary behaviour and sleep are all interrelated," he said.

"That if your child meets the guidelines for all three, they're going to have better health outcomes. 

"But that if, for example, they're just meeting the physical activity requirements, they're going to undo some of the benefits if they're spending too much time using electronic media for recreational purposes or compromising on their sleep."

Prof Okely said since the previous national guidelines relating to screen time had been released in 2012, the use of electronic media had boomed - with a myriad of devices and apps now available.

"It's important to note that the recommendations of no more than two hours of screen time a day relate to recreational sedentary screen time - while sitting or lying down," he said, "it's not referring to using electronic media for electronic purposes or homework.

"We recognise that limiting kids' screen time can be difficult for parents, so we'd suggest gradually reducing screen time or replacing it with activity. And it's important for parents to model the same behaviours too."

While at least 60 minutes of moderate to vigorous-intensity physical activity was recommended each day, Prof Okely said more was better.

"We're talking about activities like a brisk walk, swimming, dancing, active play - an activity where you can still speak while you're participating, but your heart rate is a bit faster," he said.

"Again some is better than none, and more is better than some. And it can be spread throughout the day."

When it came to sleep - children aged five to 13 years should be getting an uninterrupted nine to 11 hours of sleep a night. Those aged 14 to 17 should aim for eight to 10 hours.

"We know that many children and young people are not meeting those recommendations, however good quality sleep is vitally important," Prof Okely said.

Achieving a good balance of all three would keep kids and teens healthy and happy, he added.

"Our research shows us that meeting these guidelines leads to better cognitive development, social and emotional health and academic achievement," Prof Okely said. "And it results in lower levels of unhealthy weight and better cardio metabolic outcomes."