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Educating the Student Body
ume and heart rate, liters per minute), despite a decline in heart rate during 
growth. Similarly, increase in lung size (proportional to growth in height) 
results in greater lung volume and ventilation despite an age-associated 
decline in breathing frequency. From about age 6 to adulthood, maximal 
voluntary ventilation approximately doubles (50-100 L/min) (Malina et al., 
2004). The general pattern of increase as a function of height is similar in 
boys and girls. In both, lung function tends to lag behind the increase in 
height during the adolescent growth spurt. As a result, peak gains in lung 
function occur about 2 years earlier in girls than in boys.
Blood volume is highly related to body mass and heart size in children 
and adolescents, and it is also well correlated with maximal oxygen uptake 
during childhood and adolescence (Malina et al., 2004). Blood volume 
increases from birth through adolescence, following the general pattern 
for changes in body mass. Both red blood cells and hemoglobin have a 
central role in transport of oxygen to tissues. Hematocrit, the percentage of 
blood volume explained by blood cells, increases progressively throughout 
childhood and adolescence in boys, but only through childhood in girls. 
Hemoglobin content, which is related to maximal oxygen uptake, heart vol-
ume, and body mass, increases progressively with age into late adolescence. 
Males have greater hemoglobin concentrations than females, especially 
relative to blood volume, which has functional implications for oxygen 
transport during intense exercise.
Growth in maximal aerobic power is influenced by growth in body size, 
so controlling for changes in body size during growth is essential. Although 
absolute (liters per minute) aerobic power increases into adolescence relative 
to body weight, there is a slight decline in both boys and girls, suggesting 
that body weight increases at a faster rate than maximal oxygen consump-
tion, particularly during and after the adolescent growth spurt (Malina et 
al., 2004). Changes in maximal oxygen consumption during growth tend to 
be related more closely to fat-free mass than to body mass. Nevertheless, sex 
differences in maximal oxygen consumption per unit fat-free mass persist, 
and maximal oxygen consumption per unit fat-free mass declines with age.
Improvements in cardiorespiratory function—involving structural and 
functional adaptations in the lungs, heart, blood, and vascular system, 
as well as the oxidative capacity of skeletal muscle—occur with regular 
vigorous- and moderate-intensity physical activity (Malina et al., 2004). 
Concern about the application of invasive techniques limits the avail-
able data on adaptations in the oxygen transport system in children. 
Nevertheless, it is clear that aerobic capacity in youth increases with activ-
ity of sufficient intensity and that maximal stroke volume, blood volume, 
and oxidative enzymes improve after exercise training (Rowland, 1996). 
Training-induced changes in other components of the oxygen transport 
system remain to be determined.

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Educating the Student Body: Taking Physical Activity and Physical Education to School
Relationship to Growth, Development, and Health
 
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