Abstract
Previous studies demonstrated that the time required for oxygen uptake, CO2 production, and minute ventilation to return to baseline levels after 1-min bursts of exercise is different in children compared with adults. To test the hypothesis that the heart rate (HR) recovery time after exercise is also different in children compared with adults, we examined HR in 10 children (range 7-11 y old) and 12 adults (26-42 y old) for 10 min after 1 min of cycle ergometer exercise. Each subject exercised at work rates corresponding to 80% of the lactate or anaerobic threshold (AT), 50% of the difference between AT and maximal O2 uptake (delta), 100% of maximal uptake, and 125% of maximal uptake. Gas exchange was measured breath by breath. In adults, the HR recovery time increased significantly with work intensity as judged by the time constant of a single exponential curve fit to postburst-exercise HR [23 +/- 8 (SD) s at 80% AT, 55 +/- 16 at 50% delta, 74 +/- 13 at 100% of maximal uptake, and 83 +/- 20 at 125% of maximal uptake]. HR recovery time tended to increase with work intensity in children (16 +/- 7, 20 +/- 4, 23 +/- 7, and 27 +/- 9; for 80% AT, 50% delta, 100% of maximal uptake, and 125% of maximal uptake respectively), but to a much smaller extent, and the HR recovery time was significantly smaller in children in the high-intensity (above AT) range of exercise (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Highlights
Previous studies demonstrated that the time required for oxygen uptake, COz production, and minute ventilation to return to baseline levels after I-min bursts of exercise is different in children compared with adults
The relationship between work intensity and heart rate (HR) recovery was significantly different in children compared to adults
+ + s compared to 16 & 7 s at 80%anaerobic threshold (AT))was substantially less than in adults (e.g. H R recovery time (THR) at 125%max was 83 20 s compared to 23 8 s at 80%AT)
Summary
Previous studies demonstrated that the time required for oxygen uptake, COz production, and minute ventilation to return to baseline levels after I-min bursts of exercise is different in children compared with adults. Despite the markedly faster recoveries in children, the time course of the O 2 pulse (Voz/ HR) was indistinguishable between children and adults These data suggest that the regulation of H R after highintensity exercise is different in children compared with adults, and that the pulsatile delivery of O z to the tissues is controlled during the growth period. In previous studies of gas exchange responses to exercise, we observed that growth-related changes of V O ~ kinetics (i.e. the time course of VO?adjustments at the onset of exercise) were the same in adults and children, but dynamic ventilatory (VI-) and Vco7responses were faster in children ( I , 2). In our present investigation, the exercise duration was limited to 1 min, the work rates were scaled to the capability of each subject, and a group of prepubertal children was compared with adults
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