A Meta-Analysis of Sampled Maximal Aerobic Capacity Data for Boys Aged 11 Years Old or Less Obtained by Cycle Ergometry

Abstract

The aim of this study was to develop distributions of VO_2max based on measured values that exist in the literature in prepubertal boys using cycle ergometry. PRISMA guidelines were followed in conducting this research. One database was searched for peak and maximal VO₂ values in healthy boys with mean age under 11 years old. Data were split into articles reporting absolute and relative VO_2max values and analyzed accordingly. Multilevel models grounded in Bayesian principles were used. We investigated associations between VO_2max and body mass, year of the study, and country of origin. Differences in "peak" and "maximal" VO₂ were assessed. Absolute VO_2max (Lmin^-1) increases with age (P ~100%) but mean relative VO_2max does not change (P ~100%). Absolute VO_2max is higher in more recent studies (P = 95.7 ± 0.3%) and mean relative VO_2max is lower (P = 99.6 ± 0.1%). Relative VO_2max in the USA is lower compared with boys from other countries (P = 98.8 ± 0.2%), but there are no differences in absolute values. Mean aerobic capacity estimates presented as "peak" values are higher than "maximal" values on an absolute basis (P = 97.5 ± 0.3%) but not on a relative basis (P = 99.6 ± 0.1%). Heavier boys have lower cardiorespiratory fitness (P ≈ 100%), and body mass seems to be increasing faster with age in the USA compared with other countries (P = 92.3 ± 0.3%). New reference values for cardiorespiratory fitness are presented for prepubertal boys obtained with cycle ergometry. This is new, as no reference values have been determined so far based on actual measured values in prepubertal boys. Aerobic capacity normalized to body weight does not change with age. Cardiorespiratory fitness in prepubertal boys is declining, which is associated with increasing body mass over the last few decades. Lastly, this study did not find any statistically significant difference in the sample's mean aerobic capacity estimates using the "peak" and "maximum" distinctions identified in the literature.

Keywords: aerobic fitness; boys; children; cycle ergometry; maximal oxygen consumption.

Figure 1

Results of database searches and criteria used in the selection of studies included finding VO_2max values in boys under 11 years old.

Figure 2

Mean absolute VO_2max (Lmin⁻¹) increases with age (upper figure) in contrast to mean relative VO_2max (mLkg⁻¹min⁻¹) (lower figure) and its standard deviation, which do not change with age in boys under 11 years old.

Figure 2

Mean absolute VO_2max (Lmin⁻¹) increases with age (upper figure) in contrast to mean relative VO_2max (mLkg⁻¹min⁻¹) (lower figure) and its standard deviation, which do not change with age in boys under 11 years old.

Figure 3

The distribution of mean absolute peak VO₂ values—VO_2peak (Lmin⁻¹)—and maximal VO₂ values—VO_2max (Lmin⁻¹)—shows that mean VO_2peak is higher (upper figure). However, mean relative VO_2peak (mLkg⁻¹min⁻¹) is lower than mean relative VO_2max (mLkg⁻¹min⁻¹) (lower figure).

Figure 3

The distribution of mean absolute peak VO₂ values—VO_2peak (Lmin⁻¹)—and maximal VO₂ values—VO_2max (Lmin⁻¹)—shows that mean VO_2peak is higher (upper figure). However, mean relative VO_2peak (mLkg⁻¹min⁻¹) is lower than mean relative VO_2max (mLkg⁻¹min⁻¹) (lower figure).

Figure 4

The distribution of mean VO_2max during the years shows that more recent studies have higher values of absolute VO_2max (Lmin⁻¹) (upper figure). This is the opposite of the finding with mean relative VO_2max (mLkg⁻¹min⁻¹), which is lower in newer studies (lower figure). We can claim this with a probability of 99.57 ± 0.05%. The between-study variability seems to be dropping, and we can claim this with a probability of 90.94 ± 0.3%.

Figure 5

There are no differences in absolute VO_2max (Lmin⁻¹) between studies with subjects from USA and other countries (upper figure), but looking into studies using relative values, higher VO_2max (mLkg⁻¹min⁻¹) values were reported in subjects from other countries than in USA (lower figure). We can claim this with a probability of 98.75 ± 0.2%.

Figure 6

Absolute values of VO_2max (Lmin⁻¹) are higher in boys with greater body mass (P ≈ 100%) (upper figure), whereas mean relative VO_2max (mLkg⁻¹min⁻¹) is lower when participants have higher body mass (P ≈ 100%) (lower figure).

Figure 7

There are no significant differences between trends in articles reporting absolute VO_2max values (Lmin⁻¹) comparing USA and other countries (upper figure) as opposed to articles reporting relative VO_2max values (mLkg⁻¹min⁻¹) (lower figure). Analysis showed that in those articles’ bodies: mLkg⁻¹min⁻¹, relative cardiorespiratory fitness.