US researchers have cited that major organizations in three countries, Australia, the UK, and the US, have stated in recent years that three hours of daily exercise is optimal for children under six. Their commentary was published in the journal Archives of Pediatrics & Adolescent Medicine on Monday.

The new guidelines are partly in response to the soaring obesity rates among young children. For example, 26.7% of US children between the ages of two and five are obese or overweight, researchers Russell Pate and Jennifer O'Neill, of the University of South Carolina, wrote.

Plus, studies have shown that young children rarely get the activity they need. According to studies using accelerometers (wristwatch-like devices that measure physical activity), preschool-age kids get only sporadic exercise, with very little of it vigorous.

For children under six, experts generally advise a combination of light activity and energetic activity throughout the day. Lighter activity can be casual walking, moving around, and less energetic playtime, states the National Health Service in the UK. More energetic activities include fast walking, riding a bike, dancing, swimming, skipping rope, and active play such as hide and seek games.