Abstract
Little data are available directly comparing physiologic responses to endurance exercise
in children and adults. To evaluate age related differences during maximal and sub-maximal
treadmill exercise, physiologic parameters recorded during testing of 20 active prepubertal
boys (aged 9-13 years) were compared with values obtained in nonathletic adult males
aged 23-33 years. Maximum oxygen consumption (VO2max) was 57.9 ml · kg-1 · min-1 (6.9 SD) in the boys and 48.3 ml · kg-1 · min-1 (4.9 SD) in the adults. Running economy examined both as VO2 at a treadmill speed of 9.6 kph and as the slope of linear regression of VO2 at four submaximal speeds was less in boys compared to men when values were expressed
per kg body mass. Differences in running economy between the two groups disappeared,
however, when related to body surface area. As expected, children had a higher stride
frequency at a given treadmill speed, but running stride frequency was unrelated to
economy with the two groups. Lower respiratory exchange ratios were observed at maximal
and submaximal exercise in the children, which may reflect diminished anaerobic capacity
or differences in substrate utilization. These results substantiate the high aerobic
capacity previously observed in children and suggest that lower running economy in
younger subjects may largely relate to a greater body surface are/mass ratio.
Key words
endurance exercise - children adults running economy