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1 Universitäts-Kinderklinik, 97080 Würzburg, Germany; 2 Children's Exercise and Nutrition Centre, Chedoke Hospital, McMaster University, Hamilton, Ontario L8N 3Z5; and 3 Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
The objective of this study was to compare the
O2 uptake
(
O2) kinetics at the onset
of heavy exercise in boys and men. Nine boys, aged 9-12 yr, and 8 men, aged 19-27 yr, performed a continuous incremental cycling
task to determine peak O2
(O2 peak).
On 2 other days, subjects performed each day four cycling tasks at 80 rpm, each consisting of 2 min of unloaded cycling followed twice by
cycling at 50%
O2 peak for 3.5 min,
once by cycling at 100%
O2 peak for 2 min,
and once by cycling at 130%
O2 peak for 75 s.
O2 deficit was not significantly
different between boys and men (respectively, 50%
O2 peak task: 6.6 ± 11.1 vs. 5.5 ± 7.3 ml · min
1 · kg1;
100% O2 peak task:
28.5 ± 8.1 vs. 31.8 ± 6.3 ml · min1 · kg1;
and 130%
O2 peak
task: 30.1 ± 5.7 vs. 35.8 ± 5.3 ml · min1 · kg1).
To assess the kinetics, phase I was excluded from analysis. Phase II
O2 kinetics could be
described in all cases by a monoexponential function. ANOVA revealed no
differences in time constants between boys and men (respectively, 50%
O2 peak
task: 22.8 ± 5.1 vs. 26.4 ± 4.1 s; 100%
O2 peak task: 28.0 ± 6.0 vs. 28.1 ± 4.4 s; and 130%
O2 peak task: 19.8 ± 4.1 vs. 20.7 ± 5.7 s). In conclusion, O2 deficit and fast-component
O2 on-transients
are similar in boys and men, even at high exercise intensities, which
is in contrast to the findings of other studies employing simpler
methods of analysis. The previous interpretation that children rely
less on nonoxidative energy pathways at the onset of heavy exercise is
not supported by our findings.
oxygen uptake response; children; heavy exercise; transients
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