Three papers which between them raise controversial issues, apply laboratory measures to sport performance, and expose gaps in knowledge were selected for commentary. The first paper (Sports Med. 2016;46:1451–1460) reviews the literature on peak V̇O2 in relation to body size and recommends that peak V̇O2 in youth is best expressed via allometric scaling of lean body mass. The second paper (Pediatr Exerc Sci. 2016;28:456–465) reports that maturity status has no effect on peak V̇O2, respiratory compensation point, or ventilatory threshold in youth soccer players once data have been allometrically normalized by lower limb muscle volume. It concludes that in future this technique should be used to compare the aerobic fitness of youth soccer players. The third paper (Eur J Appl Physiol. 2016;116:1781–1794) demonstrates that V̇O2 kinetics determined in a laboratory is related to measures associated with soccer match play and might distinguish superior performance within a group of highly trained youth players. The commentary stresses the importance of experimental rigor, emphasizes the need for appropriate scaling of physiological variables, challenges spurious correlations with health-related variables, endorses the use of a range of aerobic fitness measures, welcomes the application of laboratory data to sport performance, and identifies areas for future research.
For ‘The Year that Was—2015’, I have selected 2 papers which review aspects of aerobic training. Studies of pediatric aerobic training generally focus on the effects of constant intensity exercise training (CIET) programs on peak oxygen uptake (VO2). The first paper has been chosen because it provides, for the first time, both a systematic review and a meta-analysis of the efficacy of high-intensity interval training (HIIT) in improving health-related fitness in adolescents. The second paper has been selected because it not only reviews both generic and sport-specific aerobic training studies of young team sport athletes, but also applies the analysis to the design of an evidence-based model of young athlete development. However, the primary reasons for highlighting these reviews is that they expose gaps in our knowledge of youth aerobic trainability, particularly between ‘pure’ and ‘applied’ pediatric sport science. They also identify areas where further research and appropriate data interpretation in relation to chronological age and biological maturation are required.
In Volume 1 of Pediatric Exercise Science (PES), a paper by Fenster et al. (25) investigated the relationship between peak oxygen uptake (peak V̇O2) and physical activity (PA) in 6- to 8-year-old children. They used both questionnaires and large-scale integrated activity monitors (LSIs) to estimate daily PA and determined peak V̇O2 using an incremental treadmill test to volitional exhaustion. They concluded that peak V̇O2 correlated well with PA as measured by LSIs but commented that questionnaire data were only weakly and nonsignificantly associated with LSI and peak V̇O2 data. Peak V̇O2 and PA are the most researched and reported variables in the 25-year history of PES. Yet, the assessment and interpretation of young people’s aerobic fitness and PA remain problematic and any meaningful relationship between them during childhood and adolescence is shrouded with controversy. The present paper uses Fenster et al.’s (25) report as an indicator of where we were 25 years ago, outlines how far we have advanced since then, and suggests future directions of research in the study of aerobic fitness and PA.
In the first volume of PES, Fenster et al. (25) investigated the relationship between 6- to 8-year-old children’s peak oxygen uptake (peak V̇O2) and physical activity (PA). Five boys and 13 girls participated in the study and their data were pooled for analysis. Peak V̇O2 was determined during an incremental treadmill test to voluntary exhaustion and PA was estimated using both questionnaires and large-scale integrated activity monitors (LSIs). On the basis of a significant interclass correlation coefficient of r = .59 between peak V̇O2 and the log of LSI average counts per hour Fenster et al. (25) concluded that “aerobic capacity, as measured by peak V̇O2 correlated well with physical activity as measured by LSI” (p.134).
They also commented that questionnaire data were only weakly and nonsignificantly associated with LSI and peak V̇O2 data. Young people’s peak V̇O2 and PA are the most researched and reported variables in the 25-year history of PES and yet the assessment and interpretation of peak V̇O2 and PA and any meaningful relationship between them during growth and maturation are still shrouded with controversy. The present paper uses Fenster et al.’s (25) work as an indicator of our understanding of young people’s peak V̇O2 and PA in 1989, briefly reviews what we know in 2013, and suggests future directions of research.
Three papers, which between them contribute to the current debate on the assessment and interpretation of pediatric aerobic fitness, were selected for commentary. The first paper (Children. 2017; 4:6; doi:
The presence of a maturational threshold that modulates children’s physiological responses to exercise training continues to be debated, not least due to a lack of longitudinal evidence to address the question. The purpose of this study was to investigate the interaction between swim-training status and maturity in nineteen trained (T, 10 ± 1 years, −2.4 ± 1.9 years prepeak height velocity, 8 boys) and fifteen untrained (UT, 10 ± 1 years, −2.3 ± 0.9 years prepeak height velocity, 5 boys) children, at three annual measurements.
In addition to pulmonary gas exchange measurements, stroke volume (SV) and cardiac output (Q) were estimated by thoracic bioelectrical impedance during incremental ramp exercise.
At baseline and both subsequent measurement points, trained children had significantly (p < .05) higher peak oxygen uptake (year1 T 1.75 ± 0.34 vs. UT 1.49 ± 0.22; year 2 T 2.01 ± 0.31 vs. UT 1.65 ± 0.08; year 3 T 2.07 ± 0.30 vs. UT 1.77 ± 0.16 l min−1) and Q (year 1 T 15.0 ± 2.9 vs. UT 13.2 ± 2.2; year 2 T 16.1 ± 2.8 vs. UT 13.8 ± 2.9; year 3 T 19.3 ± 4.4 vs. UT 16.0 ± 2.7 l min−1). Furthermore, the SV response pattern differed significantly with training status, demonstrating the conventional plateau in UT but a progressive increase in T. Multilevel modeling revealed that none of the measured pulmonary or cardiovascular parameters interacted with maturational status, and the magnitude of the difference between T and UT was similar, irrespective of maturational status.
The results of this novel longitudinal study challenge the notion that differences in training status in young people are only evident once a maturational threshold has been exceeded.
Neil Armstrong and Jo Welsman
Neil Armstrong and Jo Welsman
Neil Armstrong and Melitta McNarry
Peak oxygen uptake (V̇O2) is widely recognized as the criterion measure of young people’s aerobic fitness. Peak V̇O2 in youth has been assessed and documented for over 75 years but the interpretation of peak V̇O2 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 V̇O2 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 V̇O2 (pV̇O2), not peak V̇O2, which best describe aerobic fitness. There are few rigorously determined and appropriately analyzed data from young people’s pV̇O2 kinetics responses to step changes in exercise intensity. Understanding of the trainability of pV̇O2 kinetics is principally founded on comparative studies of trained and untrained youth and much remains to be elucidated. This paper reviews peak V̇O2, pV̇O2 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.
Jo Welsman and Neil Armstrong
In this paper, we draw on cross-sectional, treadmill-determined, peak oxygen uptake data, collected in our laboratory over a 20-year period, to examine whether traditional per body mass (ratio) scaling appropriately controls for body size differences in youth. From an examination of the work of pioneering scientists and the earliest studies of peak oxygen uptake, we show how ratio scaling appears to have no sound scientific or statistical rationale. Using simple methods based on correlation and regression, we demonstrate that the statistical relationships, which are assumed in ratio scaling, are not met in groups of similar aged young people. We also demonstrate how sample size and composition can influence relationships between body mass and peak oxygen uptake and show that mass exponents derived from log-linear regression effectively remove the effect of body mass. Indiscriminate use of ratio scaling to interpret young people’s fitness, to raise “Clinical Red Flags”, and to assess clinical populations concerns us greatly, as recommendations and conclusions based upon this method are likely to be spurious. We urge those involved with investigating youth fitness to reconsider how data are routinely scaled for body size.