Oxygen uptake and blood metabolic responses to a 400-m run
Résumé
This study aimed to investigate the oxygen uptake and metabolic responses during a 400-m run reproducing the pacing strategy used in competition. A portable gas analyser was used to measure the oxygen uptake (V˙O2) of ten specifically trained runners racing on an outdoor track. The tests included (1) an incremental test to determine maximal V˙O2(V˙O2max) and the velocity associated with V˙O2max(v−V˙O2max), (2) a maximal 400-m (400T) and 3) a 300-m running test (300T) reproducing the exact pacing pattern of the 400T. Blood lactate, bicarbonate concentrations [HCO−3], pH and arterial oxygen saturation were analysed at rest and 1, 4, 7, 10 min after the end of the 400 and 300T. The peak V˙O2V˙O2 recorded during the 400T corresponded to 93.9 ± 3.9% of V˙O2maxV˙O2max and was reached at 24.4 ± 3.2 s (192 ± 22 m). A significant decrease in V˙O2 (P < 0.05) was observed in all subjects during the last 100 m, although the velocity did not decrease below v−V˙O2max. The V˙O2 in the last 5 s was correlated with the pH (r = 0.86, P < 0.0005) and [HCO−3] (r = 0.70, P < 0.05) measured at the end of 300T. Additionally, the velocity decrease observed in the last 100 m was inversely correlated with [HCO−3][HCO3−] and pH at 300T (r = −0.83, P < 0.001, r = −0.69, P < 0.05, respectively). These track running data demonstrate that acidosis at 300 m was related to both the V˙O2 response and the velocity decrease during the final 100 m of a 400-m run.
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