Date Published: March 12, 2019
Publisher: Public Library of Science
Author(s): Clare C. W. Yu, Ali M. McManus, Chun T. Au, Hung K. So, Adrienne Chan, Rita Y. T. Sung, Albert M. Li, Claudio Passino.
To investigate scaling approaches for evaluating the development of peak VO2 and improving the identification of low cardiopulmonary fitness in Southern Chinese children and adolescents.
Nine hundred and twenty Chinese children and adolescents (8 to 16 years) underwent graded cardiopulmonary exercise test on a treadmill until volitional exhaustion. Peak VO2 was corrected for the effects of body mass by ratio or allometric scaling. Z score equations for predicting peak VO2 were developed. Correlations between scaled peak VO2, z scores, body size and age were tested to examine the effectiveness of the approach.
Eight hundred and fifty-two participants (48% male) were included in the analyses. Absolute peak VO2 significantly increased with age in both sexes (both P<0.05), while ratio-scaled peak VO2 increased only in males (P<0.05). Allometrically scaled peak VO2 increased from 11 years in both sexes, plateauing by 12 years in girls and continuing to rise until 15 years in boys. Allometically scaled peak VO2 was not correlated with body mass, but remained correlated with height and age in all but the older girls. Peak VO2 z score was not correlated with body mass, height or age. Absolute and allometric scaled peak VO2 values are provided for Hong Kong Chinese children and adolescents by age and sex. Peak VO2 z scores improve the evaluation of cardiopulmonary fitness, allowing comparisons across ages and sex and will likely provide a better metric for tracking change over time in children and adolescents, regardless of body size and age.
It is well established that adequate aerobic fitness is associated with reduced risk of all-cause mortality and chronic diseases across the lifespan[1–5]. Peak oxygen uptake (peak VO2) is widely recognized as one of the best indicators of aerobic fitness in the child, providing a composite measure of the pulmonary, cardiovascular, and hematological components of oxygen delivery and oxygen utilization in the exercising muscles.
A total of 1386 students were invited to join the study, of whom 281 (20%) refused to participate, 37 (3%) were excluded from the study due to their medical history, 50 (4%) were unable to attend due to their parents’ schedules, 98 (7%) could not be contacted for scheduling. Of the 920 participants who underwent CPET, 68 (7%) failed to meet the criteria for a maximal effort and were excluded. Data from 852 (410 males, 442 females) were included in the final analysis. The physical characteristics of the subjects are provided in Table 2.
Our findings demonstrate that allometric scaling of peak VO2 for body mass was effective in removing the influence of body mass on peak VO2. The scaling exponent however differed by age and sex and the scaled peak VO2 remained correlated with height, and age, within all age- and sex-specific groups, except older girls. As a result, z score equations for different sex and age groups were developed, which were effective in removing the influence of body mass, height and age on peak VO2. These provide an effective metric for identifying children with low peak VO2.
In conclusion, we have provided comparisons between different body size scaling approaches for peak VO2 in Southern Chinese girls and boys and have shown these differentially impact the interpretation of peak VO2 with changes in age and sex. We recommend the use of z scores for identifying Southern Chinese children with poor cardiopulmonary fitness, and provide an accessible data processing tools for this purpose.