Peak oxygen uptake and maturation in 12-yr olds

Is there really a proportional relationship between VO2max and body weight? A review article

Maximum oxygen uptake (VO_2max) is a “gold standard” in aerobic capacity assessment, playing a vital role in various fields. However, ratio scaling (VO2maxbw), the present method used to express relative VO_2max, should be suspected due to its theoretical deficiencies. Therefore, the aim of the study was to revise the quantitative relationship between VO_2max and body weight (bw). Dimensional analysis was utilized to deduce their theoretical relationship, while linear or nonlinear regression analysis based on four mathematical models (ratio scaling, linear function, simple allometric model and full allometric model) were utilized in statistics analysis to verify the theoretical relationship. Besides, to investigate the effect of ratio scaling on removing body weight, Pearson correlation coefficient was used to analyze the correlation between VO2maxbw and bw. All the relevant data were collected from published references. Dimensional analysis suggested VO_2max be proportional to bw23. Statistics analysis displayed that four mathematical expressions were VO_2max = 0.047bw (p<0.01, R² = 0.68), VO_2max = 0.036bw+0.71 (p<0.01, R² = 0.76), VO_2max = 0.10bw^0.82 (p<0.01, R² = 0.93) and VO_2max = 0.23bw^0.66–0.48 (p<0.01, R² = 0.81) respectively. Pearson correlation coefficient showed a significant moderately negative relation between VO2maxbw and bw (r = -0.42, p<0.01), while there was no correlation between VO2maxbw0.82 and bw (r = 0.066, p = 0.41). Although statistics analysis did not fully verify the theoretical result, both dimensional and statistics analysis suggested ratio scaling distort the relationship and power function be more appropriate to describe the relationship. Additionally, we hypothesized that lean mass, rather than body weight, plays a more essential role in eliminating the gap between theoretical and experimental b values, and is more appropriate to standardize VO_2max, future studies can focus more on it.

Moderate-to-Vigorous Physical Activity Is Associated With Cardiorespiratory Fitness Among Primary Schoolchildren Living in Côte d'Ivoire, South Africa, and Tanzania

Background: Physical inactivity and low cardiorespiratory fitness (CRF) are independent cardiovascular risk factors among children, but have rarely been investigated concurrently in sub-Saharan Africa. The purpose of this study was to compare physical activity (PA) and CRF of primary schoolchildren living in Côte d'Ivoire (CI), South Africa (ZA), and Tanzania (TZ), to test sex- and age-related differences, and to examine whether PA and CRF are associated with each other. Methods: Baseline data from an ongoing cluster-randomized controlled trial were used, including 499 children from CI (Taabo, 49% girls, M = 8.0 ± 1.6 years), 1,074 children from ZA (Gqeberha, 49% girls, M = 8.3 ± 1.4 years), and 593 children from TZ (Ifakara, 51% girls, M = 9.4 ± 1.7 years). PA was assessed by accelerometry and CRF by a 20 m shuttle-run test. The data were analyzed using multi-/univariate analyses of variance and mixed linear models. Results: Most children met recommendations put forward by the World Health Organization for moderate-to-vigorous PA (MVPA) and achieved high CRF scores. In CI, 89.6% of the children met MVPA recommendations (boys: 91.7%, girls: 87.4%), whereas this rate was 76.9% in ZA (boys: 91.0%, girls: 62.4%), and 93.8% in TZ (boys: 95.5%, girls: 92.0%). Children from TZ had the highest CRF and MVPA levels, followed by children from CI and ZA. Boys had higher MVPA levels than girls, whereas girls engaged in more sedentary behavior. Sex differences were strongest in ZA. Sedentary behavior and MVPA were higher among older schoolchildren compared to their younger peers. Higher MVPA, but not sedentary behavior, was associated with better CRF. Conclusions: In all three settings, higher levels of MVPA were associated with higher CRF scores. Nevertheless, children living in the most urbanized setting (such as observed in ZA) were physically less active and had lower CRF than peers living in more rural areas (such as observed in CI and TZ). Particularly for girls, urbanization might increase the risk for insufficient MVPA, which may have negative effects on their CRF, thus negatively influencing health and well-being at later age.

Understanding the role of aerobic fitness, spatial learning, and hippocampal subfields in adolescent males

Physical exercise during adolescence, a critical developmental window, can facilitate neurogenesis in the dentate gyrus and astrogliogenesis in Cornu Ammonis (CA) hippocampal subfields of rats, and which have been associated with improved hippocampal dependent memory performance. Recent translational studies in humans also suggest that aerobic fitness is associated with hippocampal volume and better spatial memory during adolescence. However, associations between fitness, hippocampal subfield morphology, and learning capabilities in human adolescents remain largely unknown. Employing a translational study design in 34 adolescent males, we explored the relationship between aerobic fitness, hippocampal subfield volumes, and both spatial and verbal memory. Aerobic fitness, assessed by peak oxygen utilization on a high-intensity exercise test (VO2 peak), was positively associated with the volumetric enlargement of the hippocampal head, and the CA1 head region specifically. Larger CA1 volumes were also associated with spatial learning on a Virtual Morris Water Maze task and verbal learning on the Rey Auditory Verbal Learning Test, but not recall memory. In line with previous animal work, the current findings lend support for the long-axis specialization of the hippocampus in the areas of exercise and learning during adolescence.

Traditional and New Perspectives on Youth Cardiorespiratory Fitness

PURPOSE

This study aimed to review traditional and new perspectives in the interpretation of the development of youth cardiorespiratory fitness (CRF).

METHODS

We analyzed data from (i) the literature which for 80 yr has been traditionally based on interpretations of peak oxygen uptake (V˙O2) in ratio with body mass (BM) and (ii) recent multilevel allometric models founded on 994 (475 from girls) determinations of 10- to 16-yr-olds' peak V˙O2 with measures of age, maturity status, and morphological covariates (BM and fat-free mass), and from 10 to 13 yr, 110 peak V˙O2 determinations of maximum cardiovascular covariates (stroke volume, cardiac output, and arteriovenous oxygen difference).

RESULTS

The application of ratio scaling of physiological variables requires satisfying specific statistical assumptions that are seldom met. In direct conflict with the ratio-scaled data interpretation of CRF, multilevel allometric modeling shows that with BM controlled, peak V˙O2 increases with age but the effect is smaller in girls than boys. Maturity status exerts a positive effect on peak V˙O2, in addition to those of age and BM. Changes in maximum cardiovascular covariates contribute to explaining the development of CRF, but fat-free mass (as a surrogate for active muscle mass) is the most powerful single influence. With age, maturity status, morphological covariates, and maximum cardiovascular covariates controlled, there remains an unexplained ~4% to ~9% sex difference in peak V˙O2.

CONCLUSIONS

The traditional interpretation of peak V˙O2 in ratio with BM is fallacious and leads to spurious correlations with other health-related variables. Studies of the development of CRF require analyses of sex-specific, concurrent changes in age- and maturation-driven morphological and maximum cardiovascular covariates. Multilevel allometric modeling provides a rigorous, flexible, and sensitive method of data analysis.

Modeling the dose-response rate/associations between VO2max and self-reported Physical Activity Questionnaire in children and adolescents

Background

This study sought to explore the dose-response rate/association between aerobic fitness (VO2max) and self-reported physical activity (PA) and to assess whether this association varies by sex, age, and weight status.

Methods

VO2max was assessed using the 20-m shuttle-run test. PA was assessed using the Physical Activity Questionnaire (PAQ) for Adolescents (aged >11 years, PAQ-A) or for Children (aged ≤11 years, PAQ-C). The associations between VO2max and PAQ were analyzed using analysis of covariance (ANCOVA), adopting PAQ and PAQ2 as covariates but allowing the intercepts and slope parameters of PAQ and PAQ2 to vary with the categorical variables sex, age group, and weight status.

Results

ANCOVA identified a curvilinear association between VO2max and PAQ, with positive linear PAQ terms that varied for both sex and weight status but with a negative PAQ2 term of -0.39 (95% confidence interval (CI): -0.57 to -0.21) that was common for all groups in regard to age, sex, and weight status. These curvilinear (inverted U) associations suggest that the benefits of increasing PA (same dose) on VO2max is greater when children report lower levels of PA compared to children who report higher levels of PA. These dose-response rates were also steeper for boys and were steeper for lean children compared to overweight/obese children.

Conclusion

Health practitioners should be aware that encouraging greater PA (same dose) in inactive and underweight children will result in greater gains in VO2max (response) compared with their active and overweight/obese counterparts.

Multilevel allometric modelling of maximal stroke volume and peak oxygen uptake in 11-13-year-olds

PURPOSE

To investigate (1) whether maximal stroke volume (SVmax) occurs at submaximal exercise intensities, (2) sex differences in SVmax once fat-free mass (FFM) has been controlled for, and, (3) the contribution of concurrent changes in FFM and SVmax to the sex-specific development of peak oxygen uptake [Formula: see text].

METHODS

The peak [Formula: see text] s of 61 (34 boys) 11-12-year-olds were determined and their SV determined during treadmill running at 2.28 and 2.50 m s-1 using carbon dioxide rebreathing. The SVmax and peak [Formula: see text] of 51 (32 boys) students who volunteered to be tested treadmill running at 2.50 m s-1 on three annual occasions were investigated using multilevel allometric modelling. The models were founded on 111 (71 from boys) determinations of SVmax, FFM, and peak [Formula: see text].

RESULTS

Progressive increases in treadmill running speed resulted in significant (p < 0.01) increases in [Formula: see text], but SV levelled-off with nonsignificant (p > 0.05) changes within ~ 2-3%. In the multilevel models, SVmax increased proportionally to FFM0.72 and with FFM controlled for, there were no significant (p > 0.05) sex differences. Peak [Formula: see text] increased with FFM but after adjusting for FFM0.98, a significant (p < 0.05) sex difference in peak [Formula: see text] remained. Introducing SVmax to the multilevel model revealed a significant (p < 0.05), but small additional effect of SVmax on peak [Formula: see text].

CONCLUSIONS

Fat-free mass explained sex differences in SVmax, but with FFM controlled for, there was still a ~ 5% sex difference in peak [Formula: see text]. SVmax made a modest additional contribution to explain the development of peak [Formula: see text] but there remained an unresolved sex difference of ~ 4%.

Clarity and Confusion in the Development of Youth Aerobic Fitness

Peak oxygen uptake (V˙O2) is internationally recognized as the criterion measure of youth aerobic fitness, but flawed laboratory assessments and fallacious interpretations of peak V˙O2 in ratio with body mass have confused our understanding of the development of aerobic fitness. Moreover, the recent emergence of specious predictions of peak V˙O2 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 V˙O2 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 V˙O2 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.

Interpreting Aerobic Fitness in Youth: The Fallacy of Ratio Scaling

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.

Sex-Specific Longitudinal Modeling of Youth Peak Oxygen Uptake

Purpose: To investigate peak oxygen uptake ( V˙O2 ) in relation to sex, age, body mass, fat-free mass (FFM), maturity, and overweight status. Methods: Multiplicative, allometric models of 10- to 18-year-olds were founded on 1057 determinations of peak V˙O2 supported by anthropometry and estimates of maturity status. Results: Baseline models with body mass controlled for showed age to exert a positive effect on peak V˙O2 , with negative estimates for age², sex, and a sex-by-age interaction. Sex-specific models showed maturity status to have a positive effect on peak V˙O2 in addition to the effects of age and body mass. Introducing skinfold thicknesses to provide, with body mass, a surrogate for FFM explained maturity effects and yielded a significantly (P < .05) better statistical fit in all models compared with those based on FFM estimated from youth-specific skinfold equations. With girls only, the introduction of overweight, defined by body mass index, resulted in a small but significant (P < .05) negative effect, with an age-by-overweight status interaction. Conclusions: FFM has a powerful influence on peak V˙O2 in both sexes. Interpretation of the development of youth aerobic fitness and its application to health should reflect the sex- and maturity-associated variation in FFM.

A Preliminary Study of Physical Fitness in 8- to 10-Year-Old Primary School Children From North East England in Comparison With National and International Data

Purpose: Despite recent updates to international normative values for physical fitness in young people, contemporary data sets from England are sparse with no published data available from the North East. We compared physical fitness in children from one primary school in North East England to International and European reference data, and other English regions. Methods: Eighty participants (mean age [SD]: 9.1 [0.6] y) completed a testing battery of 20-m shuttle run test, handgrip strength, standing broad jump, and sit-and-reach. Scores for each component were assessed against International or European age- and sex-specific centiles, then grouped into quintiles. Differences between our sample and European and English data sets were explored using z scores and t tests. Results: For all components, ≥58% of participants were classified as having "moderate" or lower levels. Twenty-meter shuttle run test performance was not substantially different compared with other English data sets. For handgrip and sit-and-reach, our sample scored significantly worse than South East children. Standing broad jump distance in girls, and handgrip in boys and girls, was significantly lower than North West equivalents. Conclusion: Physical fitness levels in primary school children from North East England are suboptimal, highlighting a need for large-scale monitoring studies to build on our preliminary findings.

Size Exponents for Scaling Maximal Oxygen Uptake in Over 6500 Humans: A Systematic Review and Meta-Analysis

BACKGROUND

Maximal oxygen uptake ([Formula: see text] _2max) is conventionally normalized to body size as a simple ratio or using an allometric exponent < 1. Nevertheless, the most appropriate body size variable to use for scaling and the value of the exponent are still enigmatic. Studies tend to be based on small samples and can, therefore, lack precision.

OBJECTIVE

The objective of this systematic review was to provide a quantitative synthesis of reported static allometric exponents used for scaling [Formula: see text] _2max to whole body mass and fat-free mass.

METHODS

Eight electronic databases (CINAHL, Cochrane Central Register of Controlled Trials, EMBASE, MEDLINE, PubMed, Scopus, SPORTDiscus and Web of Science) were searched for relevant studies published up to January 2016. Search terms included 'oxygen uptake', 'cardiorespiratory fitness', '[Formula: see text] _2max', '[Formula: see text] _2peak', 'scaling' and all interchangeable terms. Inclusion criteria included human cardiorespiratory fitness data; cross-sectional study designs; an empirical derivation of the exponent; reported precision statistics; and reported information regarding participant sex, age and sports background, [Formula: see text] _2max protocol, whole body composition protocol and line-fitting methods. A random-effects model was used to quantify weighted pooled exponents and 95% confidence limits (Cls). Heterogeneity was quantified with the tau-statistic (τ). Meta-regression was used to quantify the impact of selected moderator variables on the exponent effect size. A 95% prediction interval was calculated to quantify the likely range of true fat-free mass exponents in similar future studies, with this distribution used to estimate the probability that an exponent would be above theorised universal values of [Formula: see text].

RESULTS

Thirty-six studies, involving 6514 participants, met the eligibility criteria. Whole body mass and fat-free mass were used as the scaling denominator in 27 and 15 studies, respectively. The pooled allometric exponent (95% Cls) was found to be 0.70 (0.64 to 0.76) for whole body mass and 0.90 (0.83 to 0.96) for fat-free mass. The between-study heterogeneity was greater for whole body mass (τ = ±0.15) than for fat-free mass (τ = ±0.11). Participant sex explained 30% of the between-study variability in the whole body mass exponent, but the influence on the fat-free mass exponent was trivial. The whole body mass exponent of 0.52 (0.40 to 0.64) for females was substantially lower than the 0.76 (0.70 to 0.83) for males, whereas the fat-free mass exponent was similar for both sexes. The effects of all other moderators were trivial. The 95% PI for fat-free mass ranged from 0.68 to 1.12. The estimated probability of a true fat-free mass exponent in a future study being greater than [Formula: see text] power scaling is 0.98 (very likely) and 0.92 (likely), respectively.

CONCLUSIONS

In this quantitative synthesis of published studies involving over 6500 humans, the whole body mass exponent was found to be spuriously low and prone to substantial heterogeneity. We conclude that the scaling of [Formula: see text] _2max in humans is consistent with the allometric cascade model with an estimated prediction interval for the fat-free mass exponent not likely to be consistent with the [Formula: see text] power laws.

Peak oxygen uptake (VO2peak) across childhood, adolescence and young adulthood in Barth syndrome: Data from cross-sectional and longitudinal studies

Barth syndrome (BTHS) is an ultra-rare, X-linked recessive disorder characterized by cardio-skeletal myopathy, exercise intolerance, and growth delay. Oxygen uptake during peak exercise (VO2peak) has been shown to be severely limited in individuals with BTHS however; the trajectory of VO2peak from childhood to young adulthood is unknown. The objective of this study was to describe VO2peak from childhood through young adulthood in BTHS.

METHODS AND MATERIALS

VO2peak over time was presented through cross-sectional (n = 33 participants) and a longitudinal analyses (n = 12 participants). Retrospective data were obtained through maximal exercise testing on a cycle ergometer from individuals with BTHS who were or are currently enrolled in a research study during July 2006-September 2017. Participants included in the cross-sectional analysis were divided into 3 groups for analysis: 1) children (n = 13), 2) adolescents (n = 8), and 3) young adults (n = 12). Participants in the longitudinal analysis had at least two exercise tests over a span of 2-9 years.

RESULTS

VO2peak relative to body weight (ml/kgBW/min), fat-free mass (FFM) and by percent of predicted VO2peak obtained were not significantly different between children, adolescents and young adults. VO2peak did not longitudinally change over a mean time of ~5 years in late adolescent and young adult participants with repeated tests. A model including both cardiac and skeletal muscle variables best predicted VO2peak.

CONCLUSIONS

In conclusion, VO2peak relative to body weight and fat-free mass demonstrates short- and long-term stability from childhood to young adulthood in BTHS with some variability among individuals.

Top 10 Research Questions Related to Youth Aerobic Fitness

Peak oxygen uptake ([Formula: see text]₂) is internationally recognized as the criterion measure of youth aerobic fitness, but despite pediatric data being available for almost 80 years, its measurement and interpretation in relation to growth, maturation, and health remain controversial. The trainability of youth aerobic fitness continues to be hotly debated, and causal mechanisms of training-induced changes and their modulation by chronological age, biological maturation, and sex are still to be resolved. The daily physical activity of youth is characterized by intermittent bouts and rapid changes in intensity, but physical activity of the intensity and duration required to determine peak [Formula: see text]₂ is rarely (if ever) experienced by most youth. In this context, it may therefore be the transient kinetics of pulmonary [Formula: see text]₂ that best reflect youth aerobic fitness. There are remarkably few rigorous studies of youth pulmonary [Formula: see text]₂ kinetics at the onset of exercise in different intensity domains, and the influence of chronological age, biological maturation, and sex during step changes in exercise intensity are not confidently documented. Understanding the trainability of the parameters of youth pulmonary [Formula: see text]₂ kinetics is primarily based on a few comparative studies of athletes and nonathletes. The underlying mechanisms of changes due to training require further exploration. The aims of the present article are therefore to provide a brief overview of aerobic fitness during growth and maturation, increase awareness of current controversies in its assessment and interpretation, identify gaps in knowledge, raise 10 relevant research questions, and indicate potential areas for future research.

Monitoring anthropometry and fitness using maturity groups within youth rugby league

-The purpose of this study was to evaluate the anthropometry and fitness, and change in these characteristics over time, of youth rugby league players by using maturity status to determine annual categories instead of traditional chronological annual-age grouping. One hundred and twenty-one male rugby league players were assessed using anthropometric (i.e., height, sitting height, body mass, and sum of 4 skinfolds) and fitness (i.e., vertical jump, medicine ball chest throw, 10- and 20-m sprint, and multistage fitness test [MSFT]) measures over a 5-year period. Each player was classified into 1 of 6 maturity groups based on their maturity offset (years from peak height velocity, i.e., 1.5 YPHV). Multivariate analysis of variance analyses identified significant (p < 0.001) main effects for maturity group for cross-sectional characteristics and longitudinal change in performance over time. Analyses demonstrated that more mature groups had greater anthropometric and fitness characteristics, except for endurance performance (MSFT: -2.5 YPHV = 1,872 ± 18 m vs. 2.5 YPHV = 1,675 ± 275 m). For longitudinal changes in characteristics over time, a significant effect was only identified for height and sitting height (p ≤ 0.05). These findings provide comparative data for anthropometric and fitness characteristics and change in performance over time in accordance with the maturity status within youth rugby league players. Classifying players into annual maturity groups may be an additional or alternative assessment method for evaluating anthropometry and fitness performance in adolescent populations. Furthermore, tracking performance changes over time, especially in relation to maturation, may reduce the limitations associated with chronological annual-age grouping.

A influência do desenvolvimento sexual sobre as qualidades físicas básicas de meninos adolescentes

<p><strong>Objetivo</strong> O objetivo deste estudo foi avaliar os efeitos da maturação sexual sobre parâmetros antropométricos e das qualidades físicas básicas em adolescentes de dez a quatorze anos do sexo masculino.</p><p><strong>Materiais e Métodos</strong> Para verificar a idade biológica observaram-se os estágios de desenvolvimento da genitália externa. As outras características avaliadas foram: massa corporal total (MCT), a estatura e o índice de massa corporal (IMC), idade óssea (IO), força, velocidade, agilidade e potência aeróbica.</p><p>Resultados Os resultados demonstraram diferenças significativas em todas as variáveis ligadas ao crescimento (idade cronológica, estatura, massa corporal total, índice de massa corporal e idade óssea) entre os diferentes estágios de maturação sexual. Em relação às qualidades físicas, entre os estágios maturacionais, encontraram-se diferenças significativas na maioria dos parâmetros avaliados, com exceção da agilidade.</p><p><strong>Conclusão</strong> Conclui-se com este estudo, que a maturação sexual avaliada através dos estágios de desenvolvimento da genitália externa exerceu grande influência sobre variáveis antropométricas, a idade óssea e as qualidades físicas básicas dos adolescentes avaliados.</p>

Muscle metabolism changes with age and maturation: How do they relate to youth sport performance?

AIM

To provide an evidence-based review of muscle metabolism changes with sex-, age- and maturation with reference to the development of youth sport performance.

METHODS

A narrative review of data from both invasive and non-invasive studies, from 1970 to 2015, founded on personal databases supported with computer searches of PubMed and Google Scholar.

RESULTS

Youth sport performance is underpinned by sex-, age- and maturation-related changes in muscle metabolism. Investigations of muscle size, structure and metabolism; substrate utilisation; pulmonary oxygen uptake kinetics; muscle phosphocreatine kinetics; peak anaerobic and aerobic performance; and fatigue resistance; determined using a range of conventional and emerging techniques present a consistent picture. Age-related changes have been consistently documented but specific and independent maturation-related effects on muscle metabolism during exercise have proved elusive to establish. Children are better equipped for exercise supported primarily by oxidative metabolism than by anaerobic metabolism. Sexual dimorphism is apparent in several physiological variables underpinning youth sport performance. As young people mature there is a progressive but asynchronous transition into an adult metabolic profile.

CONCLUSIONS

The application of recent developments in technology to the laboratory study of the exercising child and adolescent has both supplemented existing knowledge and provided novel insights into developmental exercise physiology. A sound foundation of laboratory-based knowledge has been established but the lack of rigorously designed child-specific and sport-specific testing environments has clouded the interpretation of the data in real life situations. The primary challenge remains the translation of laboratory research into the optimisation of youth sports participation and performance.

Cardiorespiratory fitness, respiratory function and hemodynamic responses to maximal cycle ergometer exercise test in girls and boys aged 9-11 years: the PANIC Study

PURPOSE

We aimed to provide comprehensive data on and reference values for cardiorespiratory fitness, respiratory function and hemodynamic responses during and after maximal cycle ergometer test in children.

METHODS

The participants were a population sample of 140 children (69 girls) aged 9-11 years. Heart rate (HR) and systolic blood pressure (SBP) were measured from pre-exercise rest to the end of recovery. Respiratory gases were measured directly by the breath-by-breath method. Peak workload, HR changes, peak oxygen uptake (VO2), peak oxygen pulse (O2 pulse), peak respiratory exchange ratio (RER) and the lowest ratio of ventilation and carbon dioxide output (VE/VCO2) during the exercise test in girls and boys were presented according to their distributions in 5 categories.

RESULTS

HR decreased more during 4-min recovery in boys than in girls (76 vs. 67 beats/min, p < 0.001), whereas SBP decrease was similar in boys and girls (30 vs. 22 mmHg, p = 0.66). Boys had a higher peak VO2 per weight [51.9 vs. 47.6 ml/kg/min, p < 0.001] and per lean mass [67.3 vs. 63.0 ml/kg/min, p < 0.001] than girls. Peak O2 pulse per lean mass was higher in boys than in girls (0.34 vs. 0.31 ml/kg/beat, p < 0.001). There was no difference in the lowest VE/VCO2 during the test between boys and girls (28 vs. 29, p = 0.18).

CONCLUSIONS

The indicators of cardiorespiratory fitness were better in boys than in girls. These data enable the evaluation of cardiorespiratory function during and after maximal exercise test and the detection of children with abnormal values.

Scaling of peak oxygen uptake in children: a comparison of three body size index models

PURPOSE

We aimed to compare three candidate body size index models for the scaling of aerobic fitness (V(˙)O(2peak)) in children: whole body mass, total lean body mass, and the lean mass of both legs.

METHODS

V(˙)O(2peak) and total lean mass of the body and both legs (via dual-energy x-ray absorptiometry) were assessed in 126 girls and 87 boys aged 9-11 yr. We applied nonlinear allometric models of the form V(˙)O(2peak) = a×body size, adjusted for biological sex and maturity offset (years from peak height velocity). We assessed goodness of fit using the Akaike information criterion.

RESULTS

The Akaike weights (Akaike differences) were as follows: lean mass of both legs = 0.69 (0), total lean body mass = 0.31 (1.6), and whole body mass = <1e-8 (36.6). The size exponent (90% confidence interval) for the lean mass of both legs was 0.55 (0.46-0.64). V(˙)O(2peak) was 17% (13%-21%) lower in girls after controlling for the lean mass of both legs and maturity offset. After controlling for body size and sex, a 1-yr increase in maturity offset (closer to peak height velocity) was associated with a 6% (4%-9%) higher V(˙)O(2peak).

CONCLUSIONS

Allometric scaling of V(˙)O(2peak) by the lean mass of both legs provides the best model for quantifying growth-related changes in aerobic fitness in pediatric populations, although this model is only marginally superior to the total lean body mass model. There is no support for the total body mass model. Maturity and sex are also important covariates exerting a size-independent influence on peak aerobic fitness.

[Association between nutritional status and physical abilities in children aged 6 to 18 years in Medellin (Colombia)]

INTRODUCTION

Nutritional disorders in childhood may cause a decline in motor abilities and increased morbidity and mortality in adulthood.

OBJECTIVE

To assess the association between nutritional status and motor abilities.

MATERIALS AND METHODS

A cross-sectional study was performed that included 12,872 children aged between 6 and 18 years who underwent a clinical evaluation and various physical tests.

RESULTS

Among the children, 66% had a Tanner maturation stage 1 and 2, 6% were under-nourished, and 12.2% were at risk of overweight and obesity. The obese children had a decrease in aerobic power (in 2.72 mL O2 kg(-1)·min(-1); 95%CI: 1.89 to 3.56; P<.001), speed (0.14m·sec; 95%CI: 0.06 to 0.22; P<.001), explosive strength (0.10 m; 95%CI: 0.06 to 0.13; P<.001), agility, strength endurance and balance. Under-nourished children showed a decrease in speed (0.13 m·sec; 95%CI: 0.06 to 0.20; P<.001), explosive strength (0.04 m; 95%CI: 0.01 to 0 07; P<.004), and strength endurance.

CONCLUSIONS

There was an association between nutritional status and motor abilities in the children included in this study. Obese children showed the worst results in physical tests, and the under-nourished ones showed a decrease in speed, explosive strength and strength endurance.

An individualized longitudinal approach to monitoring the dynamics of growth and fitness development in adolescent athletes

This study evaluated the development of anthropometric and fitness characteristics of 3 individual adolescent junior rugby league players and compared their characteristics with a cross-sectional population matched by age and skill level. Cross-sectional anthropometric and fitness assessments were conducted on 1,172 players selected to the Rugby Football League's talent development program (i.e., the Player Performance Pathway) between 2005 and 2008. Three players of differing relative age, maturational status, and playing position were measured and tracked once per year on 3 occasions (Under 13s, 14s, 15s age categories) and compared against the cross-sectional population. Results demonstrated that the later maturing players increased height (player 1 = 9.2%; player 2 = 7.8%) and a number of fitness characteristics (e.g., 60-m speed-player 1 = -14.9%; player 2 = -9.9%) more than the earlier maturing player (player 3-Height = 2.0%, 60-m sprint = -0.7%) over the 2-year period. The variation in the development of anthropometric and fitness characteristics between the 3 players highlights the importance of longitudinally monitoring individual characteristics during adolescence to assess the dynamic changes in growth, maturation, and fitness. Findings showcase the limitations of short-term performance assessments at one-off time points within annual-age categories, instead of advocating individual development and progression tracking without deselection. Coaches should consider using an individual approach, comparing data with population averages, to assist in the prescription of appropriate training and lifestyle interventions to aid the development of junior athletes.

Motor impairment and its relationship to fitness in children

OBJECTIVES

The aim of this work was to explore the physiological and perceptual limits to exercise in children with varying degrees of motor impairment, and the relationships to measures of health.

DESIGN AND METHODS

In a group comparison design, 35 boys aged 12-15 years completed the Movement ABC test for the assessment of motor impairment, followed by an incremental cycle ergometer test to exhaustion for the assessment of maximal oxygen uptake (VO2peak), respiratory exchange ratio (RER), heart rate (HR) and rating of perceived exertion (RPE). Ten participants classified as having either high or no motor impairment also performed a maximal voluntary isometric contraction (MVIC) for the assessment of lower limb extensor strength.

RESULTS

18 boys were classified as having high motor impairment. There was a significant difference in peak (34.9 vs 48.5 mL kg/min), workload (12.5 vs 10.0 mL W), maximal HR (176 vs 188 bpm), maximal oxygen pulse (12.1 vs 15.9 mL beat) and MVIC (5.7 vs 9.1 Nm kg) between the high and non-motor impaired participants, respectively, (p<0.05). There was no significant difference in the RER or RPE between groups.

CONCLUSIONS

When performing cycling ergometry, perceived exertion was not a limiting factor in children with high motor impairment. The lower maximal HR, coupled with reduced movement efficiency and muscle strength reported in this group, suggests that exercise is limited by impairment at the muscular level. This finding was supported by high RER values despite low maximal HR values attained at exercise cessation and reduced maximal strength. Perception of effort is not heightened in children with high motor impairment and future-exercise interventions should be focused on improving muscular condition in these participants to enable them to be better prepared to engage in physical activity for health.

The relationship among HRpeak, RERpeak, and VO2peak during treadmill testing in girls

Clear criteria for maximal oxygen consumption (VO2max) determination in youth are not available, and no studies have examined this issue in girls. Our purpose was to determine whether different peak heart rate (HRpeak) and peak respiratory exchange ratio (RERpeak) cut points affect girls' (N = 453; M age = 13.3 years, SD = .1) VO2max during a maximal treadmill test. A multivariate analysis of variance revealed VO2max (ml kg(-1) min(-1) differed significantly among HRpeak, 180-189 b min(-1) = 34 (SD = .8), 190-194 bmin(-1) = 35 (SD = .9), 195-199 b min(-1) = 38 (SD = .8), 200-204 b min(-1) = 40 ml kg1 x min(-1) (SD = .8), and > or = 205 bmin(-1) = 42 ml kg1 x min(-1) (SD = .7) but not RERpeak. In studies where evidence of a VO2 plateau was examined, peak oxygen consumption (VO2peak) did not differ between plateau and no-plateau groups. Although our results suggest the association between lower VO2peak and lower peak heart rate is a true cardiovascular limit to aerobic energy production, we cannot rule out participant effort.

Expiratory flow limitation during exercise in prepubescent boys and girls: prevalence and implications

The purpose of this study was to compare the prevalence and implications of expiratory flow limitation (EFL) during exercise in boys and girls. Forty healthy, prepubescent boys (B; n = 20) and girls (G; n = 20) were tested. Subjects completed pulmonary function tests and an incremental cycle maximal oxygen uptake (V̇o2max) test. EFL was recorded at the end of each exercise stage using the % tidal volume overlap method. Ventilatory and metabolic data were recorded throughout exercise. Arterial oxygen saturation (SpO2) was determined via pulse oximetry. Body composition was determined using dual-energy X-ray absorptiometry. There were no differences ( P > 0.05) in height, weight, or body composition between boys and girls. At rest, boys had significantly higher lung volumes (total lung capacity, B = 2.6 ± 0.5 liters, G = 2.1 ± 0.5 liters) and peak expiratory flow rates (B = 3.6 ± 0.6 l/s; G = 1.6 ± 0.3 l/s). Boys also had significantly higher V̇o2max (B = 46.9 ± 5.9 ml·kg lean body mass−1·min−1, G = 41.7 ± 6.6 ml·kg lean body mass−1·min−1) and maximal ventilation (B = 49.8 ± 8.8 l/min, G = 41.2 ± 8.3 l/min) compared with girls. There were no sex differences ( P > 0.05) at V̇o2max in VE /Vco2, end-tidal Pco2, heart rate, respiratory exchange ratio, or SpO2. The prevalence (B = 19/20 vs. G = 18/20) and severity (B = 58 ± 7% vs. G = 43 ± 8% tidal volume) of EFL was not significantly different in boys compared with girls at V̇o2max. A significant relationship existed between % EFL at V̇o2max and the change in end-expiratory lung volume from rest to maximal exercise in boys ( r = 0.77) and girls ( r = 0.75). In summary, our data suggests that EFL is highly and equally prevalent in prepubescent boys and girls during heavy exercise, which led to an increased end-expiratory lung volume but not to decreases in arterial oxygen saturation.

The fall and rise of the gender difference in elite anaerobic performance 1952-2006

PURPOSE

To compare the historical evolution of performance for males and females in anaerobically dominated sprint events in three different sports: running, swimming, and speed skating.

METHODS

Times of the top six finishers in a total of 283 men's and women's Olympic and world championship finals held between 1952 and 2006 were analyzed, and performance differences between males and females were calculated for each final position.

RESULTS

After a relatively faster rate of improvement among females from the 1950s to a nadir in the 1980s, the gender difference in anaerobic performance at the highest levels of international competition has actually increased during the last 15 yr. Overall, the time-based performance difference for all six events analyzed has increased from a low of 10.3% in the period 1976-1988 to a current difference of 11.5% for the period 2000-2005.

CONCLUSIONS

Analysis of elite sprinting performance in running, swimming, and speed skating during the last 50 yr reveals that the performance difference between males and females has ceased to narrow and has actually widened since the mid-1990s. The change observed cannot be explained by declining women's participation in sport, poorer training practice, or reduced access to technological developments, but it does coincide with dramatic improvements in the scope and sensitivity of drug testing. Current gender differences in performance, and the underlying differences in performance power, may now reasonably reflect the true physiological differences between males and females.

The relationship between heart rate reserve and oxygen uptake reserve in children and adolescents

The purpose of the present study was to examine the relationship between oxygen uptake (VO2) and heart rate (HR) responses during rest and exercise in Chinese children and youth and to evaluate the relationships between maximal heart rate (%HRmax), heart rate reserve (%HRR), peak oxygen uptake (% VO2peak), and oxygen uptake reserve (% VO2R) in Chinese children and youth. Forty-nine Chinese children and youth were studied at rest and during a graded maximal exercise test on treadmill. Resting, submaximal and peak HR and VO2 were collected. Regression analyses were conducted to investigate the associations between the various forms of HR and VO2 measures. The equivalency between %HRR and % VO2R for adults was examined for children using data obtained in this study. Results indicated that all regression lines between HR measures and VO2 measures were significantly different from the line of identity (p < .05), except the regression line for %HRR versus %VO2 peak in boys. The equivalency between % VO2R and % HRR for adults was not demonstrated in children and adolescents in this study. In contrast, %HRR was more closely equivalent to % VO2 peak. Because a strong linear relationship was found between HR and VO2, HR measures, in terms of either %HRmax or %HRR, would still be a practical variable for prescribing appropriate exercise intensity for children and adolescents. Unlike results found for adults, a given % HRR in children and youth was not equivalent to its corresponding % VO2R.

Evidence for secular trends in children's physical activity behaviour

It is not clear whether the global increase in weight problems in children is the result of excessive energy intake or decreasing energy expenditure. Methodological limitations have made it difficult to analyse. There is evidence that at least part of the problem may lie with increasing energy consumption, but it is important to examine the other side of the energy equation also. However, it is not possible to conclusively describe physical activity trends because of the absence of suitable baseline data. One solution is to summate all available evidence in as many areas of daily activities as possible and then draw tentative conclusions. This review summarises available trend data on direct representations of physical activity in a range of contexts, together with indirect measures such as sedentariness, fitness, and attitudes. The conclusions drawn are: physical activity in clearly defined contexts such as active transport, school physical education, and organised sports is declining in many countries; young people would like to be active but are often constrained by external factors such as school policy or curricula, parental rules in relation to safety and convenience, and physical environmental factors.

Do custom-made mouth guards have negative effects on aerobic performance capacity of athletes?

Mouth guards are considered an essential part of equipment for athletes participating in contact sports. The purpose of this study was to evaluate the effect of custom-made mouth guards on the ventilatory gas exchange effects of taekwondo athletes. The subjects were 22 elite athletes aged between 14 and 17 years. To determine the effect of mouth guard use during exercise, oxygen consumption (VO(2)) was measured with a portable gas analysis system while an exercise tolerance test with a shuttle run test protocol was performed. Values with and without mouth guard were compared. Wilcoxon ranks test was used for the statistical analysis. The results show that wearing mouth guards has no significant effect on maximal oxygen uptake (VO(2max)), minute ventilation (VE), tidal volume (VT) and respiratory exchange ratio (RER) while performing maximal exercise (P > 0.05). In conclusion, taekwondo athletes can use custom-made mouth guards without negative effects on their aerobic performance capacity.

Exercise as a modality in the treatment of childhood obesity

In a review of the literature, Glenny et al determined that family therapy and lifestyle modification seem to be effective in the prevention and treatment of childhood but not necessarily adult obesity. Furthermore, research indicates that obese children are better able to maintain weight loss over a long-term period than are adults. Based on the limited research in the treatment of obesity in children, approaches should include family interventions with nutrition and physical activity education, structured exercise, and behavior modification. These interventions should be delivered by a team of health care experts in a nurturing, nonintimidating environment; however, obese children respond differently physiologically and emotionally to exercise than do normal-weight children. Therefore, obese children may experience negative consequences to participation in activities considered appropriate for normal-weight children. In clinical settings, specialized exercise programs based on appropriate theories that include specific recommendations for children with varied obese conditions have been shown to enhance safety, efficacy, and compliance during pediatric obesity treatment. Optimal results may be achieved by combining programs to reduce sedentary behaviors based on similar theories with specialized, structured exercise prescriptions. When used in conjunction with appropriate dietary prescriptions and consistent behavior modification, exercise serves as a promising modality that may reverse obese conditions during childhood and, perhaps, prevent the onset of adult obesity.

Scaling peak V˙o 2 to body mass in young male and female distance runners

This study examined age- and sex-associated variation in peak oxygen consumption (V˙o 2) of young male and female distance runners from an allometric scaling perspective. Subjects were from two separate studies of 9- to 19-yr-old distance runners from the mid-Michigan area, one conducted between 1982 and 1986 (Young Runners Study I, YRS I) and the other in 1999–2000 (Young Runners Study II, YRS II). Data from 27 boys and 27 girls from YRS I and 48 boys and 22 girls from the YRS II were included, and a total of 139 and 108 measurements of body size and peak V˙o 2 in boys and girls, respectively, were available. Subjects were divided into whole year age groups. A 2 × 9 (sex × age group) ANOVA was used to examine differences in peakV˙o 2. Intraindividual ontogenetic allometric scaling was determined in 20 boys and 17 girls measured annually for 3–5 yr. Allometric scaling factors were calculated using linear regression of log-transformed data. Results indicated that 1) absolute peak V˙o 2increases with age in boys and girls, 2) relative peakV˙o 2(ml · kg−1 · min−1) remains relatively stable in boys and in girls, 3) relative peakV˙o 2(ml · kg−0.75 · min−1) increases throughout the age range in boys and increases in girls until age 15 yr, and 4) peakV˙o 2 adjusted for body mass (ml/min) increases with age in boys and girls. The overall mean cross-sectional scaling factor was 1.01 ± 0.03 (SE) in boys and 0.85 ± 0.05 (SE) in girls. Significant age × sex interactions and significant scaling factors between sexes identify the progressive divergence of peak V˙o 2 between adolescent male and female distance runners. Mean ontogenetic allometric scaling factors were 0.81 [0.71–0.92, 95% confidence interval (CI)] and 0.61 (0.50–0.72, 95% CI) in boys and girls, respectively ( P = 0.002). There was considerable variation in individual scaling factors (0.51–1.31 and 0.28–0.90 in boys and girls, respectively). The results suggest that the interpretation of growth-related changes in peak V˙o 2 of young distance runners is dependent upon the manner of expressing peakV˙o 2 relative to body size and/or the statistical technique employed.

Longitudinal changes in submaximal oxygen uptake in 11- to 13-year-olds

The aim of this study was to monitor longitudinal changes in young people's submaximal oxygen uptake (VO2) responses during horizontal treadmill running at 8 km x h(-1). The 236 participants (118 boys, 118 girls) were aged 11.2+/-0.4 years (mean +/- s) at the onset of the study. Submaximal VO2, peak VO2 and anthropometry were recorded annually for three consecutive years. The data were analysed using multi-level regression modelling within a multiplicative, allometric framework. The initial model examined sex, age and maturity-related changes in submaximal VO2 relative to body mass as the sole anthropometric covariate. Our results demonstrate that the conventional ratio standard ml x kg(-1) x min(-1) does not adequately describe the true relationship between body mass and submaximal VO2 during this period of growth. The effects of maturity and age were non-significant, but girls consumed significantly less VO2 than boys running at 8 km x h(-1). In subsequent models, stature was shown to be a significant explanatory variable, but this effect became non-significant when the sum of two skinfolds was added. Thus, within this population, submaximal VO2 responses were explained predominantly by changes in body mass and skinfold thicknesses, with no additional maturity-related increments. When differences in body mass and skinfolds were controlled for, there was still a difference between the sexes in submaximal VO2, with girls becoming increasingly more economical with age.

Modeling growth and maturation changes in peak oxygen uptake in 11-13 yr olds

The influence of gender, growth, and maturation on peak O(2) consumption (VO(2 peak)) in 11-13 yr olds were examined by using multilevel regression modeling. Subjects were 119 boys and 115 girls, aged 11.2 +/- 0.4 (SD) yr at the onset of the study. Sexual maturation was classified according to Tanner's indexes of pubic hair. VO(2 peak) was determined annually for 3 yr. The initial model identified body mass and stature as significant explanatory variables, with an additional positive effect for age and incremental effects for stage of maturation. A significant gender difference was apparent with lower values for girls, and an age-by-gender interaction indicated a progressive divergence in boys' and girls' VO(2 peak). Subsequent incorporation of the sum of two skinfold thicknesses into the model negated stature effects, reduced the gender term, and explained much of the observed maturity effects. The body mass exponent almost doubled, but the age-by-gender interaction term was consistent with the initial model.

Submaximal exercise and maturation in 12-year-olds

The aim of this study was to examine the maturation responses of young people to submaximal treadmill exercise. Body mass was controlled using both the conventional ratio standard and allometric modelling. Ninety-seven boys and 97 girls with a mean age of 12.2 years completed a discontinuous, incremental exercise test to voluntary exhaustion. We measured peak oxygen uptake (VO2peak) and VO2 when running at 8, 9 and 10 km x h(-1). Sexual maturation was assessed visually using Tanner's indices of pubic hair. Peak VO2 was significantly higher in boys (P<0.001); this was still the case when the influence of body mass was covaried out. During submaximal exercise, no significant differences in absolute VO2 were observed between the sexes (P>0.05); however, values of VO2, expressed both in ratio with body mass and adjusted for body mass using allometry, were significantly greater in boys than in girls (P<0.001). For absolute VO2, significant main effects (P<0.05) were seen for maturity at each exercise stage. With the influence of body mass controlled using either the ratio standard or allometry, no significant main effects (P>0.05) for maturity were observed. Our results indicate that boys are less economical than girls while running at 8-10 km x h(-1) and that, independently of body mass, maturation does not influence the VO2 response to submaximal exercise.