The slow component of O-2 uptake kinetics during high-intensity exercise in trained and untrained prepubertal children

The aim of the present study was to investigate the O-2 uptake slow compone nt in prepubertal children of different aerobic capacity during high intens ity exercise. Twenty-three (12 well-trained, T and 11 untrained, U subjects ) 10 - 13 year old prepubertal children took part in 3 tests: one increment al test to determine the maximal aerobic power (PMA) and anaerobic threshol d (LAT); two constant-power tests performed at intensities corresponding to 80%LAT and 90%PMA. Oxygen uptake ((V) over dot O-2), heart rate, ventilati on ((V) over dot E) and lactate ([L]s) were evaluated during each test. A m onoexponential + linear term model (starting after phase 1) was used to ass ess (V) over dot O-2 kinetics during both constant-power tests. Our results showed that a slow component, represented by the linear coefficient (5) of the mathematical model, was present during the 90%PMA test only (S = 0.86 +/- 0.48 ml x min(-2) x kg(-1) for the whole population). No relationships were found between either S and (V) over dot E or [L]s, showing that, at le ast in prepubertal children, these factors play a minor role in the explana tion for the (V) over dot O-2 slow component. The slow component contribute d approximately to the same amount of the total (V) over dot O-2 response i n both groups (T: 21.4 +/- 8.0, U: 19.3 +/- 3.9%, ns). In conclusion, as pr eviously described in adults, our data demonstrated the existence of a slow component in prepubertal children during high-intensity exercise. Moreover , this slow component was similar in trained and untrained children, exerci sing at the same relative intensity.