The results about the influence of bicarbonate ingestion on performance are contradictory (1). Several studies have demonstrated no ergogenic effect of bicarbonate ingestion on high-intensity exercise performance, despite significant blood alkalosis (2), although there are not studies in field conditions during bicycle motocross (BMX) competitions. Therefore, the aim of the study was to examine the effect of sodium bicarbonate ingestion on a specific test based in field conditions, analyzing the acid-base status and the cardiorespiratory response and its influence on performance. Ten elite BMX riders participated in this study which consisted in two trials performed in separated days. Each trial included three consecutive BMX races in field conditions separated by 15 min recovery. The experiment was carried out in a BMX track to simulate a real competition. Ninety minutes prior to exercise subjects ingested either NaHCO3- (0.3 g.kg-1 body weight) or placebo. The two treatments conditions were administered in a counterbalanced, crossover, randomly assigned and double-blind manner. Expired air and blood samples were collected for the assessment of cardiorespiratory and blood acid-base response, respectively. Oxygen uptake (VO2), ventilation (VE), pH and blood lactate concentration ([La-]) were measured. Performance variable of race time was measured for each BMX race (R) repetition. Two way ANOVA with repeated measures were used to determine differences between treatments at each exercise moment. Both conditions (bicarbonate and placebo) showed a similar response (p>0.05) of VO2 (1999±361 vs. 2090±467 mL.min-1 after R1; 2142±490 vs. 2229±428 mL.min-1 after R2; 2143±440 vs. 2171±359 mL.min-1 after R3, respectively) and VE (70.8±28.2 vs. 72.1±27.6 L.min-1 after R1; 72.9±26.5 vs. 73.7±29.4 L.min-1 after R2; 76.9±23.9 vs. 79.3±28.7 L.min-1 after R3, respectively). The ingestion of NaHCO3- had the expected effect on blood pH, since remained reduced (p<0.05) across experimental protocol in the placebo condition (7.18±0.05 vs. 7.12±0.05 3 min after R1; 7.14±0.07 vs. 7.06±0.03 3 min after R2, bicarbonate vs. placebo conditions, respectively). No significant differences were found in the [La-] between both conditions, with higher values in the bicarbonate condition (13.5±2.9 vs. 12.1±2 mmol.L-1 3 min after R1; 15.5±2.8 vs. 14.03±0.8 mmol.L-1 3 min after R2; 16.8±2.5 vs. 16.5±1.8 mmol.L-1 3 min after R3, respectively). Race time was similar in each race between conditions (p>0.05) (31.4±1.3 vs. 31.1±1.05 s R1; 31.2±1.3 vs. 31±1.04 s R2; 31.3±1.2 vs. 31.05±1.04 s R3, bicarbonate vs. placebo conditions, respectively). Sodium bicarbonate ingestion modified significantly the blood acid-base balance, although the attenuated acidosis did not improve the performance across three consecutive races in field conditions in elite BMX cyclists.