• physical fitness

Increasingly it is recognised that what happens in childhood has a significant impact on health in adulthood. As we and others have shown—social, emotional, cognitive and physical development in childhood and adolescence tracks through to later life.1 2 The paper by Tomkinson and colleagues3 examined trends in cardiorespiratory fitness (CRF) levels in childhood and adolescence. It is an important piece of work because poor fitness levels in adolescence are significantly linked with higher all-cause mortality rates later in life4 and because, as the authors illustrate in their comprehensive study, CRF fitness levels in children and adolescents in high-income and high-middle-income countries have significantly declined since the 1980s.

There is some relief in the fact that since 2000 the rate of decline has slowed significantly. A question to ask is whether the reason for a slower decline to do with the fact that there is not much more ‘fitness’ to cut back on. We are also interested in the sex differences between base levels of fitness but the paper does not extend that far, and there is also no mention of the technological revolution seen in terms of children’s modern ‘toys’, and …