"This calls into question popular opinion, as well as guidelines published by numerous organisations recommending limits on backpack weights for children. Globally, there’s been little agreement on what a limit should be. Guidelines vary, with the limit being anywhere between 5% and 20% of body weight."

"Preventing mental illness is just as important as preventing other chronic conditions such as heart disease, diabetes and cancer. As with these chronic conditions, regular physical activity plays a key role."

"To understand why the timing of exercise might be important, we first need to understand how our bodies function over a 24-hour day. Our biological clock helps to regulate sleep patterns, when we eat, blood pressure and body temperature. These “circadian rhythms” have been associated with many aspects of physical performance, health and well-being."