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Study: Ramp up physical activity and sleep to boost kids' bone health

Study: Ramp up physical activity and sleep to boost kids' bone health


Children need more moderate-to-vigorous physical activity, more sleep and less sedentary time to optimize bone health, according to a University of South Australia study.

The study found the ideal balance of a child's activities across a 24-hour period comprises:

  • 1.5 hours of moderate-to-vigorous physical activity (sports, running around)
  • 3.4 hours of light physical activity (walking, doing chores)
  • 8.2 hours of sedentary time (studying, sitting at school, reading)
  • 10.9 hours of sleep.

"Children's activities throughout the whole 24-hour day are important for their bone health, but until now we haven't known the perfect combination of exercise, sleep and sedentary time," said Dr. Dot Dumuid, lead researcher from the University of South Australia. "Higher levels of physical activity are known to be good for children's bone health, yet we can't just increase children's exercise without impacting their other activities.”

More than 800 Australian children between the ages of 11 and 13 were part of the study.  

"In this study, we looked at the interrelating factors of physical activity (both light and moderate-to-vigorous physical activity), sedentary time and sleep, finding an ideal combination that delivers the best daily balance,” Dumuid said. "The 'Goldilocks Day' tells us the durations of physical activity, sleep and sitting that are 'just right' for children's optimal bone health. Up to 90 percent of peak bone mass is achieved by age 18-20, which makes this especially important during childhood and adolescence. Optimizing bone health in children is a key protector against osteoporosis, the leading preventable cause of fracture in adults and a major public health problem with considerable economic and societal costs.”

Globally, osteoporosis affects 200 million people, with 75 million cases across Europe, the United States, and Japan.

The study also highlights the importance of sleep, especially for boys.

"We always talk about getting enough exercise to help build bones, but for children it's vital that they also get enough sleep,” Dumuid said. "Curiously, the study also showed that sleep is more important for boys' bone health than for girls, with boys needing an extra 2.4 hours of sleep a day. However, boys tended to be at earlier stages of pubertal development than girls, causing us to speculate that the need for longer sleep is related to rapidly changing hormonal processes rather than gender. By knowing the best balances and interrelations of sleep, exercise and rest, parents and caregivers can guide their child's daily activities to put them in good stead for future bone health."

Bone Health Exercise Health Sleep Study

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