Clarity and Confusion in the Development of Youth Aerobic Fitness

Abstract

Peak oxygen uptake ( ) is internationally recognized as the criterion measure of youth aerobic fitness, but flawed laboratory assessments and fallacious interpretations of peak in ratio with body mass have confused our understanding of the development of aerobic fitness. Moreover, the recent emergence of specious predictions of peak from performance tests and the promotion of spurious “clinical red flags” and cardiometabolic cut-points have confused our understanding of the relationship between youth aerobic fitness and health. Recent longitudinal studies of 10–18-year-olds using multilevel allometric modeling have empirically demonstrated that peak increases in accord with sex-specific, concurrent changes in age- and maturity status-driven morphological covariates with the timing and tempo of changes specific to individuals. During both cycle ergometry and treadmill running age- and maturity status- driven changes in fat free mass have been revealed as the most powerful morphological influences on the development of youth aerobic fitness. To bring some clarity to current confusion, this paper argues that future studies must be founded on rigorous assessment and interpretation of peak and ensure that they address the development of youth aerobic fitness and its relationship with present and future health in relation to appropriate sex-specific morphological covariates governed by individual biological clocks.

Associations between cardiorespiratory fitness, motor competence, and adiposity in children

“…Nevertheless, we also showed that higher VȮ 2peak scaled by BM was associated with better MC and lower BF% suggesting that the previous observations on the positive associations of MC with CRF and the modifying role of CRF in the associations between MC and BF% are largely influenced by body composition rather than peak aerobic power. 18,22 T A B L E 2 Associations of peak oxygen uptake (VȮ Although we found weak and statistically insignificant association between VȮ 2peak scaled by LM, MC, and BF%, we observed that W max scaled either by LM or BM was positively associated with MC. We also found a weak inverse association between W max scaled by LM and BF% in the PANIC Study, which is in contrast to the results with VȮ 2peak .…”

“…Our findings do not support previous findings on the positive associations of MC and CRF in children. 6 A reason for these divergent results is that previous studies have used body size and composition confounded measures of CRF, 16,18,22,31 such as 20-m shuttle run test 6 or VȮ 2peak scaled by BM, 13,14 while we utilized VȮ 2peak scaled by LM that is the preferred method to normalize CRF for body size and composition. 22 Furthermore, we found a weak and statistically insignificant relationship of VȮ 2peak scaled by LM to BF% while we observed a strong inverse association between VȮ 2peak scaled by BM and BF%.…”

“…V̇O 2peak depends on the capacity of cardiovascular system to deliver oxygenated blood to the working muscle and the ability of muscle tissue to utilize oxygen to support mechanical work 18 . Maximal cardiac output has been found to be the strongest determinant of V̇O 2peak during exercise 19,20 .…”

“…[15][16][17] VȮ 2peak depends on the capacity of cardiovascular system to deliver oxygenated blood to the working muscle and the ability of muscle tissue to utilize oxygen to support mechanical work. 18 Maximal cardiac output has been found to be the strongest determinant of VȮ 2peak during exercise. 19,20 Muscle mass, that is an active tissue during exercise, is the main driver of absolute cardiac output and VȮ 2peak, 21 while fat mass, that is included in BM, does not contribute to cardiac output or VȮ 2peak .…”

Bidirectional associations between fitness and fatness in youth: A longitudinal study

“…22 Third, the use of a ratio-scaled value of CRF (absolute VO 2 divided by body weight) may hamper the correct interpretation of the association between fitness and fatness. 59 In the case of the 20-m shuttle run test, participants have to carry their weight over a series of 20-m shuttle runs, which adversely affects performance in the heavier participants. 60 Nonetheless, we used an equation to estimate CRF that was validated without correcting the test performance by any anthropometric measure.…”