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      Sodium citrate supplementation enhances tennis skill performance: a crossover, placebo-controlled, double blind study

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          The efficacy of sodium citrate supplementation (SC) in exercise performance is unclear. Therefore, the aim of this study was to investigate the effect of SC on skilled tennis performance.


          Ten Brazilian nationally-ranked young male tennis players (age: 17 ± 1 yrs.; stature: 176.7 ± 5.2 cm; body mass: 68.4 ± 7.9 kg) participated in this crossover, placebo-controlled, double-blind study. Upon arrival, at baseline, in both experimental sessions blood was collected, then subjects ingested either sodium citrate (SC - 0.5 g .kg −1BM in capsules of 500 mg) or a placebo (PLA). Two hours later, pre-match blood was collected then skills tests (skill tennis performance test - STPT, repeated-sprint ability shuttle test - RSA) were performed followed by a 1-h simulated match. Immediately following the match, blood was again collected, and STPT, and RSA were administered.


          All metabolic parameters (i.e. base excess, pH, bicarbonate, and blood lactate) increased ( p < 0.001) from baseline to pre-match and post-match in SC condition. Each metabolic parameter was greater (p < 0.001) in SC compared to PLA condition at both pre- and post-match. The SC condition elicited a greater ( p < 0.01) shot consistency at post-match in the STPT vs. PLA condition (SC: 58.5 ± 14.8% vs. PLA: 40.4 ± 10.4%). A greater ( p < 0.001) amount of games won was observed in the simulated match for SC condition vs. PLA condition (SC: 8.0 ± 1.6 vs. PLA: 6.0 ± 1.7). Additionally, the games won during the simulated match in SC condition was positively correlated with percentage shot consistency (r = 0.67, p < 0.001).


          The current findings suggest that SC supplementation is an effective ergogenic aid to enhance skilled tennis performance.

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          Most cited references 40

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          Effects of acute alkalosis and acidosis on performance: a meta-analysis.

          Ingestion of agents that modify blood buffering action may affect high-intensity performance. Here we present a meta-analysis of the effects of acute ingestion of three such agents - sodium bicarbonate, sodium citrate and ammonium chloride - on performance and related physiological variables (blood bicarbonate, pH and lactate). A literature search yielded 59 useable studies with 188 observations of performance effects. To perform the mixed-model meta-analysis, all performance effects were converted into a percentage change in mean power and were weighted using standard errors derived from exact p-values, confidence limits (CLs) or estimated errors of measurement. The fixed effects in the meta-analytic model included the number of performance-test bouts (linear), test duration (log linear), blinding (yes/no), competitive status (athlete/nonathlete) and sex (male/female). Dose expressed as buffering mmoL/kg/body mass (BM) was included as a strictly proportional linear effect interacted with all effects except blinding. Probabilistic inferences were derived with reference to thresholds for small and moderate effects on performance of 0.5% and 1.5%, respectively. Publication bias was reduced by excluding study estimates with a standard error >2.7%. The remaining 38 studies and 137 estimates for sodium bicarbonate produced a possibly moderate performance enhancement of 1.7% (90% CL ± 2.0%) with a typical dose of 3.5 mmoL/kg/BM (∼0.3 g/kg/BM) in a single 1-minute sprint, following blinded consumption by male athletes. In the 16 studies and 45 estimates for sodium citrate, a typical dose of 1.5 mmoL/kg/BM (∼0.5 g/kg/BM) had an unclear effect on performance of 0.0% (±1.3%), while the five studies and six estimates for ammonium chloride produced a possibly moderate impairment of 1.6% (±1.9%) with a typical dose of 5.5 mmoL/kg/BM (∼0.3 g/kg/BM). Study and subject characteristics had the following modifying small effects on the enhancement of performance with sodium bicarbonate: an increase of 0.5% (±0.6%) with a 1 mmoL/kg/BM increase in dose; an increase of 0.6% (±0.4%) with five extra sprint bouts; a reduction of 0.6% (±0.9%) for each 10-fold increase in test duration (e.g. 1-10 minutes); reductions of 1.1% (±1.1%) with nonathletes and 0.7% (±1.4%) with females. Unexplained variation in effects between research settings was typically ±1.2%. The only noteworthy effects involving physiological variables were a small correlation between performance and pre-exercise increase in blood bicarbonate with sodium bicarbonate ingestion, and a very large correlation between the increase in blood bicarbonate and time between sodium citrate ingestion and exercise. The approximate equal and opposite effects of sodium bicarbonate and ammonium chloride are consistent with direct performance effects of pH, but sodium citrate appears to have some additional metabolic inhibitory effect. Important future research includes studies of sodium citrate ingestion several hours before exercise and quantification of gastrointestinal symptoms with sodium bicarbonate and citrate. Although individual responses may vary, we recommend ingestion of 0.3-0.5 g/kg/BM sodium bicarbonate to improve mean power by 1.7% (±2.0%) in high-intensity races of short duration.
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            Induced metabolic alkalosis affects muscle metabolism and repeated-sprint ability.

            The purpose of this study was to assess the effects of induced metabolic alkalosis, via sodium bicarbonate (NaHCO3) ingestion, on muscle metabolism and power output during repeated short-duration cycle sprints. : Ten active females (mean +/- SD: age = 19 +/- 2 yr, VO2max = 41.0 +/- 8.8 mL x kg x min ) ingested either 0.3 g x kg NaHCO3 or 0.207 g x kg of NaCl (CON), in a double-blind, random, counterbalanced order, 90 min before performing a repeated-sprint ability (RSA) test (5 x 6-s all-out cycle sprints every 30 s). Compared with CON, there was a significant increase in resting blood bicarbonate concentration [HCO3] (23.6 +/- 1.1 vs 30.0 +/- 3.0 mmol x L ) and pH (7.42 +/- 0.02 vs 7.50 +/- 0.04), but no significant difference in resting lactate concentration [La] (0.8 +/- 0.2 vs 0.8 +/- 0.3 mmol x L ) during the NaHCO3 trial. Muscle biopsies revealed no significant difference in resting muscle [La], pH, or buffer capacity (beta(in vitro)) between trials (P > 0.05). Compared with CON, the NaHCO3 trial resulted in a significant increase in total work (15.7 +/- 3.0 vs 16.5 +/- 3.1 kJ) and a significant improvement in work and power output in sprints 3, 4, and 5. Despite no significant difference in posttest muscle pH between conditions, the NaHCO3 trial resulted in significantly greater posttest muscle [La]. As NaHCO3 ingestion does not increase resting muscle pH or beta(in vitro), it is likely that the improved performance is a result of the greater extracellular buffer concentration increasing H efflux from the muscles into the blood. The significant increase in posttest muscle [La] in NaHCO3 suggests that an increased anaerobic energy contribution is one mechanism by which NaHCO3 ingestion improved RSA.
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              Sodium bicarbonate and high-intensity-cycling capacity: variability in responses.

              To determine whether gastrointestinal (GI) distress affects the ergogenicity of sodium bicarbonate and whether the degree of alkalemia or other metabolic responses is different between individuals who improve exercise capacity and those who do not.

                Author and article information

                J Int Soc Sports Nutr
                J Int Soc Sports Nutr
                Journal of the International Society of Sports Nutrition
                BioMed Central (London )
                1 August 2019
                1 August 2019
                : 16
                [1 ]ISNI 0000 0001 0723 2494, GRID grid.411087.b, School of Applied Sciences, , University of Campinas, ; Rua Pedro Zaccaria 1300, Limeira, 13484-350 Sao Paulo Brazil
                [2 ]ISNI 0000 0004 1937 0722, GRID grid.11899.38, School of Arts, Sciences and Humanities, , University of Sao Paulo, ; Sao Paulo, Sao Paulo Brazil
                [3 ]ISNI 0000 0004 0635 0263, GRID grid.255951.f, Department of Exercise Science and Health Promotion, Muscle Physiology Laboratory, , Florida Atlantic University, ; Kissimme, Florida USA
                [4 ]ISNI 0000 0004 1937 0722, GRID grid.11899.38, School of Physical Education and Sport, , University of Sao Paulo, ; Sao Paulo, Sao Paulo Brazil
                © The Author(s). 2019

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

                Funded by: FundRef, Fundação de Amparo à Pesquisa do Estado de São Paulo;
                Award ID: 2012/19529-9
                Award Recipient :
                Research Article
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                © The Author(s) 2019

                Sports medicine

                fatigue, buffering agent, tennis skills, blood lactate, supplementation


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