Dose-related elevations in venous pH with citrate ingestion do not alter 40-km cycling time-trial performance

The purpose of the current investigation was to determine whether sodium ci trate enhances endurance cycling performance and, if so, what dosage(s) pro duces this effect. Eight trained [peak power output: 362 (48) W; power:weig ht: 5.1 (0.4) W . kg(-1), mean (SD)] male cyclists were requested to comple te four, 40-km time-trials. each separated by 3-7 days, on their own bicycl es, mounted on a Kingcycle ergometer. To mimic the stochastic nature of cyc le road races, the time-trials included four 500-m, four 1-km and two 2-km sprints. The experimental conditions involved the ingestion of three dosage s of sodium citrate dissolved in 400 mi water: 0.2 g . kg(-1) 0.4 g . kg(-1 ) and 0.6 g . kg(-1) body mass (b.m.) and a placebo (calcium carbonate, 0.1 g . kg(-1) b.m.). Subjects were asked to complete both the sprints and tot al distance in the fastest time possible. Venous blood samples were collect ed before, as well as at 10-km intervals during the trials for the analysis of plasma lactate and glucose concentrations and for the measurement of bl ood pH and PCO2 levels, Immediately before, as well as during exercise, pH was significantly higher in the group ingesting the highest citrate dose (r ange 7.36-7.45) compared to the placebo (range 7.31-7.39) and the two lower citrate dosages. Despite this, no significant differences in power output (P = 0.886) or time taken to complete the 40 km (P = 0.754) were measured b etween the four trials. The average performance times (in min:s, with SD in parentheses) and average power output (in W) for the 40-km time-trials wer e: 58:46 (5:06) [265 (62) W], 60:24 (6:07) [251 (59) W], 61:47 (5:07) [243 (44) W] and 60:02 (5.05) [255 (55) W] for the 0.2, 0.4 0.6 g . kg(-1) b.m. sodium citrate and placebo trials, respectively. There were also no signifi cant differences measured between treatments in terms of time, power output , speed or heart rate during the 500-m, 1-km and 2-km sprints. The ingestio n of increasing sodium citrate dosages before exercise produced dose-depend ent changes in pH, base excess and HCO3- concentrations before and during t he 40-km time-trial. However, these changes influenced neither the time-tri al time nor the sprinting performance times.