Aim: To analyse aerobic fitness and its relationship with sport participation, exercise training and habitual physical activity (HPA) during youth.
Methods: Studies were located through computer searches of Medline, SPORT Discus and personal databases. Systematic reviews of time trends in aerobic fitness/performance, and exercise training and peak oxygen uptake (peak VO(2)) are reported.
Results: Peak VO(2) increases with age and maturation. Boys' peak VO(2) is higher than girls'. Despite data showing a decrease in performance test estimates of aerobic fitness there is no compelling evidence to suggest that young people have low levels of peak VO(2) or that it is declining over time. The primary time constant of the VO(2) kinetics response to moderate and heavy intensity exercise slows with age and the VO(2) kinetics response to heavy intensity exercise is faster in boys. There is a negative correlation between lactate threshold as a percentage of peak VO(2) and age but differences related to maturation or sex remain to be proven. Young athletes have higher peak VO(2), a faster primary time constant and accumulate less blood lactate at the same relative exercise intensity than their untrained peers. Young people can increase their peak VO(2) through exercise training but a meaningful relationship between aerobic fitness and HPA has not been demonstrated.
Conclusions: During youth the responses of the components of aerobic fitness vary in relation to age, maturation and sex. Exercise training will enhance aerobic fitness but a relationship between young people's current HPA and aerobic fitness remains to be proven.