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

Abstract

The purpose of the current investigation was to determine whether sodium citrate enhances endurance cycling performance and, if so, what dosage(s) produces this effect. Eight trained [peak power output: 362 (48) W; power:weight: 5.1 (0.4) W x kg(-1), mean (SD)] male cyclists were requested to complete four, 40-km time-trials, each separated by 3-7 days, on their own bicycles, mounted on a Kingcycle ergometer. To mimic the stochastic nature of cycle 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 dosages of sodium citrate dissolved in 400 ml water: 0.2 g x kg(-1), 0.4 g x kg(-1) and 0.6 g x kg(-1) body mass (b.m.) and a placebo (calcium carbonate, 0.1 g x kg(-1) b.m.). Subjects were asked to complete both the sprints and total distance in the fastest time possible. Venous blood samples were collected 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 blood pH and PCO2 levels. Immediately before, as well as during exercise, pH was significantly higher in the group ingesting the highest citrate dose (range 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 between 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 were: 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 x kg(-1) b.m. sodium citrate and placebo trials, respectively. There were also no significant 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 ingestion of increasing sodium citrate dosages before exercise produced dose-dependent changes in pH, base excess and HCO3- concentrations before and during the 40-km time-trial. However, these changes influenced neither the time-trial time nor the sprinting performance times.

Caffeine Ingestion Does Not Alter Performance during a 100-km Cycling Time-Trial Performance

“…Indeed in a previous study employing shorter 40-km time trials, which also included repeated HIE, we (39) found that sprinting performance fell progressively as did blood lactate concentrations, whereas pH rose, the opposite of the predicted effect if fatigue is regulated by peripheral metabolites.…”

“…Indeed, the noteworthy feature of this and other studies (33,36,37,39) is the reproducibility of the pacing strategies used by subjects during closed trials of the type used in this study. This invites the question of the nature of the internal physiological cues that determine such a response, since the subjects in all our trials receive no external cues other than the distance covered.…”

From catastrophe to complexity: a novel model of integrative central neural regulation of effort and fatigue during exercise in humans: summary and conclusions

“…13 14 More probably, a developing metabolic acidosis may induce a progressively increasing homoeostatic respiratory compensation, which increases the perception of discomfort, at the same time producing a compensatory alkalosis. 16 This escalating discomfort ultimately causes the conscious decision to terminate the exercise bout. 15 Furthermore, skeletal muscle ATP concentrations are never reduced to less than 50% of the resting value under all conditions of exercise, including maximal exercise in persons with a reduced capacity to generate ATP either oxidatively or glycolytically, or in muscles rendered ischaemic by the application of a tourniquet and forced to contract until exhaustion by external stimulation.…”

Acute versus chronic supplementation of sodium citrate on 200 m performance in adolescent swimmers

“…However, the gastrointestinal (GI) acceptance profile of sodium bicarbonate is narrow and 10% of humans cannot adequately tolerate the doses needed to elicit an ergogenic effect [6,9]. Thus, ingesting sodium bicarbonate in high enough doses to induce an adequate modification of the acid–base balance during exercise can be detrimental to performance [6,9,10]. Sodium citrate (Na-CIT) is another alkalizing agent that has been studied in sports over a broad array of doses, times and distances but the results on its ergogenic effect have been inconclusive [2-4,10-14].…”

“…Thus, ingesting sodium bicarbonate in high enough doses to induce an adequate modification of the acid–base balance during exercise can be detrimental to performance [6,9,10]. Sodium citrate (Na-CIT) is another alkalizing agent that has been studied in sports over a broad array of doses, times and distances but the results on its ergogenic effect have been inconclusive [2-4,10-14]. Indeed, the meta-analysis by Carr et al [8] reported an unclear effect on performance (0.0 ± 1.3%) for a 60 sec maximal effort, with a dose of 0.5 g kg -1 .…”