Oxygen uptake and blood metabolic responses to a 400-m run

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 \( \left( {\dot{V}{{{\text{O}}_{ 2} }} } \right) \) of ten specifically trained runners racing on an outdoor track. The tests included (1) an incremental test to determine maximal \( \dot{V}{{{\text{O}}_{ 2} }} \,\left( {\dot{V}{{{\text{O}}_{{ 2 {\text{max}}}} }} } \right) \) and the velocity associated with \( \dot{V}{{{\text{O}}_{{ 2 {\text{max}}}} }} \left( {{\text{v}}-\dot{V}{{{\text{O}}_{{ 2 {\text{max}}}} }} } \right), \) (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 \( \left[ {{\text{HCO}}_{ 3}^{ - } } \right], \) 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 \( \dot{V}{{{\text{O}}_{ 2} }} \) recorded during the 400T corresponded to 93.9 ± 3.9% of \( \dot{V}{{{\text{O}}_{2\max } }} \) and was reached at 24.4 ± 3.2 s (192 ± 22 m). A significant decrease in \( \dot{V}{{{\text{O}}_{ 2} }} \) (P < 0.05) was observed in all subjects during the last 100 m, although the velocity did not decrease below \( {\text{v}}-\dot{V}_{{{\text{O}}_{{ 2 {\text{max}}}} }} . \) The \( \dot{V}{{{\text{O}}_{ 2} }} \) in the last 5 s was correlated with the pH (r = 0.86, P < 0.0005) and \( \left[ {{\text{HCO}}_{ 3}^{ - } } \right] \) (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 \( \left[ {{\text{HCO}}_{ 3}^{ - } } \right] \) 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 \( \dot{V}{{{\text{O}}_{ 2} }} \) response and the velocity decrease during the final 100 m of a 400-m run.