THE EFFECT OF ACUTE-HYPOXIA AT LOW-ALTITUDE AND ACUTE NORMOXIA AT HIGH-ALTITUDE ON PERFORMANCE DURING A 30-S WINGATE TEST IN CHILDREN

The effect of acute hypoxia (FIO2 = 0.137 +/- 0.001) at Low Altitude ( LA: Clermont-Ferrand, 330 m) and acute normoxia (FIO2 = 0.306 +/- 0.00 6) at High Altitude (HA: La Pat, 3600 m) on performance during a 30-s Wingate test has been investigated in prepubertal children (Tanner sta ge 1). Twenty five boys (LA, n = 10; HA, n = 15) aged from 10.6 to 12. 7 years performed two Wingate tests at random: at LA, one in normoxia (ambient air) and one in acute hypoxia and at HA, one in chronic hypox ia (ambient air) and one in acute normoxia. The subjects performed the two tests using the same calibrated cycle ergometer. Peak Power (PP), Mean Power (MP), O-2 uptake during the 30s (VO2) and blood lactate ac cumulation (Delta[L]s) were measured. Compared to normoxia, acute hypo xia at LA did not alter PP (8.0 +/- 1.1 vs 7.9 +/- 1.3 W.kg(-1) BW) an d MP (6.1 +/- 0.7 vs 6.1 +/- 1.1 W.kg(-1) BW). Similarly compared to c hronic hypoxia, acute normoxia at HA did not modify these parameters ( PP: 7.4 +/- 1.5 vs 7.3 +/- 1.8; MP: 5.4 +/- 1.2 vs 5.5 +/- 1.1; W.kg(- 1) BW). VO2 and Delta[L]s were neither significantly changed by acute hypoxia at LA (520 +/- 50 vs 550 +/- 60 ml O-2; 5.3 +/- 1.7 vs 4.8 +/- 1.7 mmol.l(-1)) nor by acute normoxia at HA (530 +/- 110 vs 500 +/- 9 0 ml O-2; 3.4 +/- 1.3 vs 3.3 +/- 1.0 mmol.l(-1)). When comparing HA an d LA (chronic situation), VO2 was similar at HA and LA but Delta[L]s w as reduced at HA; however chronic hypoxia did not alter Wingate perfor mances. Thus, in prepubertal children, modifications of O-2 fractions of inspired air did not alter MP, blood lactate accumulation and aerob ic contribution to a 30-s Wingate test.