Oxygen Uptake Kinetics in Youth: Characteristics, Interpretation, and Application

Abstract

Pulmonary oxygen uptake (V  O2) kinetics, which describe the aerobic response to near instantaneous changes in metabolic demand, provide a valuable insight into the control and coordination of oxidative phosphorylation during exercise. Despite their applicability to the highly sporadic habitual physical activity and exercise patterns of children, relatively little is known regarding the influence of internal and external stimuli on the dynamic V  O2 response. Whilst insufficient evidence is available during moderate intensity exercise, an age-related slowing of the phase II time constant (τ) and augmentation of the V  O2 slow component appears to be manifest during heavy intensity exercise, which may be related to changes in the muscle phosphate controllers of oxidative phosphorylation, muscle oxygen delivery and utilisation and/or muscle fibre type recruitment patterns. Similar to findings in adults, aerobic training is associated with a faster phase II τ and smaller V  O2 slow component in youth, independent of age or maturity, indicative of an enhanced oxidative metabolism. However, a lack of longitudinal or intervention-based training studies limit our ability to attribute these changes to training per se. Further, methodologically rigorous studies are required to fully resolve the interaction(s) between age, sex, biological maturity and external stimuli, such as exercise training and exercise intensity, and the dynamic V  O2 response at the onset and offset of exercise.

Relationship between (non)linear phase II pulmonary oxygen uptake kinetics with skeletal muscle oxygenation and age in 11–15 year olds

“…) coheres with that observed for muscle kinetics (Benson, Grassi, & Rossiter, ; Grassi et al., ; Krustrup, Jones, Wilkerson, Calbet, & Bangsbo, ), or, as its surrogate, phosphocreatine (PCr) breakdown in adults (Rossiter et al., ) and children (Barker et al., ). However, whilst a progressive slowing of the in older adults (Babcock, Paterson, Cunningham, & Dickinson, ; DeLorey, Kowalchuk, & Paterson, ) has been reported to originate during childhood (see McNarry, for a recent review), the physiological factors limiting kinetics remain less well understood in youths.…”

Youth Aerobic Fitness

“…She takes the opportunity to expand her analysis of the sparse research, critically examines the evidence supporting the existence of child-adult differences, questions aspects of the differential muscle-activation hypothesis, and identifies areas for further research. Taken together, the thought-provoking contributions of Dotan (22) and McNarry (34,35) remind us that much remains to be learned about the mechanisms underpinning the development of pulmonaryVO 2 dynamics in childhood and adolescence.…”

“…In a Letter to the Editor, Dotan (22) argues that children are more limited than adults in their capacity to recruit and utilize higher threshold type II motor units and reviews the role of the child-adult differential muscle-activation hypothesis in explaining why children have fasterVO 2 kinetics than adults. He suggests that the hypothesis is able to account, as a sole or major underlying factor, for all the mechanisms, proposed by McNarry (35), as partial explanations for adult-child differences. In her response, McNarry (34) acknowledges that different child-adult fiber-type distribution and recruitment may contribute to an exploration of child-adult differences but contends that there is insufficient evidence to support the view that the differential muscle-activation hypothesis provides the sole or major explanation.…”

“…Mel McNarry (35) focuses her invited review on pulmonarẏ VO 2 kinetics in youth and emphasizes the need for rigor in the analysis of data with a low signal to noise ratio. She discusses how flawed methodology and misinterpretation of rich data sets have clouded understanding of young people's transient responses at the onset and offset of exercise.…”

“…One of the strengths of the review is a discussion of the potential mechanistic bases of age-, sex-, and training-induced changes in pulmonaryVO 2 kinetics. McNarry (35) concludes that more methodologically rigorous studies are required to resolve the influence of and interactions between sex, age, maturity status, and external stimuli (eg, training) on the development of the dynamic pulmonaryVO 2 responses at the onset and offset of exercise.…”