Evolution of maximal oxygen uptake in children.

Evidence exists that physiologic aerobic fitness, defined by maximal oxygen uptake related to body mass (VO2 x kg-1), bears health implications for children as well as adults. Identifying secular trends in VO2max x kg-1 is important, then, in assessing the impact of socio-cultural influences on aerobic fitness in youth. At present, no data exist to provide a population-based indication of secular trends in VO2max in young persons. However, based on documented temporal changes in childhood obesity and physical activity levels, it can be anticipated that a decline of VO2max x kg-1 is occurring over time. This fall would be more likely due to increases in body fat in youth, inflating the size-normalizing factor ('per kg'), rather than a temporal deterioration in cardiovascular function per se.