Aerobic Fitness and Trainability in Healthy Youth: Gaps in Our Knowledge

Peak oxygen uptake (VO2) is widely recognized as the criterion measure of young people's aerobic fitness. Peak VO2 in youth has been assessed and documented for over 75 years but the interpretation of peak VO2 and its trainability are still shrouded in controversy. Causal mechanisms and their modulation by chronological age, biological maturation and sex remain to be resolved. Furthermore, exercise of the intensity and duration required to determine peak VO2 is rarely experienced by most children and adolescents. In sport and in everyday life young people are characterized by intermittent bouts of exercise and rapid changes in exercise intensity. In this context it is the transient kinetics of pulmonary VO2 (pVO2), not peak VO2, which best describe aerobic fitness. There are few rigorously determined and appropriately analyzed data from young people's pVO2 kinetics responses to step changes in exercise intensity. Understanding of the trainability of pVO2 kinetics is principally founded on comparative studies of trained and untrained youth and much remains to be elucidated. This paper reviews peak VO2, pVO2 kinetics, and their trainability in youth. It summarizes "what we know," identifies significant gaps in our knowledge, raises relevant questions, and indicates avenues for future research.