The Effect of Individual Sodium Citrate Consumption on Repeated Sprint Performance in Female Soccer Players

Official title

The Acute Effects of Individually Timed Sodium Citrate Ingestion on Repeated Sprint Performance in Professional Female Soccer Players: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

Overview

The aim of this research is to determine whether sodium citrate supplementation, taken at the best individual time, would improve repeated sprint performance in professional female soccer players. The main questions it aims to answer are: 1. Does sodium citrate improve sprint times, peak power, minimum power, and mean power during repeated sprints? 2. Does sodium citrate lower fatigue index (the drop in power across sprints) during repeated sprint exercise? 3. Does sodium citrate change blood bicarbonate, pH, and lactate levels before and after exercise? 4. Does sodium citrate affect how hard exercise feels (perceived exertion)?

Detailed description

This study is a randomized, double-blind, placebo-controlled crossover trial designed to investigate the effects of acute sodium citrate (SC) supplementation on repeated sprint performance and acid-base responses in female soccer players. Based on an a priori sample size calculation using G\*Power (version 3.1), a minimum of 20 participants is required and will be recruited. Eligible participants will be professional female soccer players competing in the Turkish Women's Third League.

Each participant will complete two experimental trials in a randomized order, separated by a washout period of at least three days. During the SC trial, participants will ingest SC at a dose of 0.5 g·kg-¹ body mass dissolved in a flavored beverage. During the placebo (PL) trial, participants will consume a taste- and appearance-matched sodium chloride solution. Both supplements will be prepared by a researcher not involved in data collection to ensure allocation concealment and maintenance of double blinding.

On each experimental visit, participants will arrive at the laboratory following an overnight fast and will consume a standardized breakfast before supplementation. Capillary blood samples will be collected before supplementation and at regular intervals thereafter to determine blood bicarbonate concentration. During the SC condition, exercise testing will commence once blood bicarbonate concentration has increased by at least 5.0 mmol·L-¹ above baseline (individualized peak bicarbonate response; Tpeak). During the placebo condition, exercise testing will begin 120-150 minutes after ingestion, corresponding to the expected time window for peak bicarbonate responses observed during SC supplementation. To minimize the influence of hormonal fluctuations on exercise performance and physiological responses, both experimental trials will be conducted during the same phase of the menstrual cycle, outside the menstruation period. Participants using oral contraceptives will be excluded.

Repeated sprint performance will be assessed using the Running-based Anaerobic Sprint Test (RAST), which consists of six maximal 35-m sprints separated by 10 seconds of passive recovery. Sprint performance outcomes will include sprint times, peak power, minimum power, mean power, and fatigue index. Capillary blood samples will be collected at baseline, immediately before exercise, and immediately after exercise to determine blood bicarbonate concentration, blood pH, and lactate concentration. Ratings of perceived exertion (RPE) will be recorded after each sprint using the Borg 6-20 scale. The success of participant blinding will be evaluated using a blinding questionnaire administered at three predefined time points during the study.

Interventions

• Dietary supplement Sodium Citrate Oral Product
  0.5 g/kg body weight of sodium citrate dissolved in flavored water, ingested orally. Exercise begins at individual peak blood bicarbonate time (T\_peak), determined through serial capillary blood sampling starting 90 minutes post-ingestion.
• Other Placebo
  Sodium chloride (NaCl) at a taste-matched dose dissolved in flavored water, ingested orally. Exercise begins 120-150 minutes post-ingestion.

Primary outcome measures

• Minimum Power [Time frame: Measured during the RAST test, administered immediately after the individualized ingestion-to-exercise interval (T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo)]
• Fatigue Index [Time frame: Measured during the RAST test, administered immediately after the individualized ingestion-to-exercise interval (T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo)]

Secondary outcome measures (7)

• Peak Power [Time frame: Measured during the RAST test, administered immediately after the individualized ingestion-to-exercise interval (T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo)]
• Mean Power [Time frame: Measured during the RAST test, administered immediately after the individualized ingestion-to-exercise interval (T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo)]
• Sprint Times [Time frame: Measured during the RAST test, administered immediately after the individualized ingestion-to-exercise interval (T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo)]
• Blood Bicarbonate Concentration [Time frame: Measured at baseline (pre-ingestion), pre-exercise (at T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo), and at 1, 3, 5, and 7 minutes post-exercise.]
• Blood pH [Time frame: Measured at baseline (pre-ingestion), pre-exercise (at T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo), and at 1, 3, 5, and 7 minutes post-exercise.]
• Blood Lactate Concentration [Time frame: Measured at baseline (pre-ingestion), pre-exercise (at T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo), and at 1, 3, 5, and 7 minutes post-exercise.]
• Rating of Perceived Exertion (RPE) [Time frame: Measured after each sprint during the RAST test, administered immediately after the individualized ingestion-to-exercise interval (T_peak for sodium citrate; 120-150 minutes post-ingestion for placebo)]

Eligibility criteria

Inclusion criteria

• Female professional soccer players competing in the Turkish Women's Third League
• Age between 18-25 years
• Active training status (minimum 3 sessions per week)
• Regular menstrual cycles
• Both experimental trials scheduled in the same phase of the menstrual cycle, outside of menstruation
• No use of nutritional supplements in the 4 weeks prior to the study
• Willingness to provide written informed consent

Exclusion criteria

• Use of oral contraceptives
• Irregular menstrual cycle
• History of gastrointestinal disorders
• Any musculoskeletal injury preventing maximal sprint performance
• Smoking
• Use of any medication that may affect acid-base balance
• Pregnancy

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Crossover

Masking

Double blind

Primary purpose

Basic science

Study locations

Center list to be confirmed — check the primary protocol.

Publications

• Peacock J, Sparks SA, Middlebrook I, Hilton NP, Tinnion D, Leach N, Saunders B, McNaughton LR. Extracellular buffer choice influences acid-base responses and gastrointestinal symptoms. Res Sports Med. 2021 Nov-Dec;29(6):505-516. doi: 10.1080/15438627.2021.1896517. Epub 2021 Mar 9. PMID 33715526
• Lancha Junior AH, Painelli Vde S, Saunders B, Artioli GG. Nutritional Strategies to Modulate Intracellular and Extracellular Buffering Capacity During High-Intensity Exercise. Sports Med. 2015 Nov;45 Suppl 1:S71-81. doi: 10.1007/s40279-015-0397-5. PMID 26553493
• McNulty KL, Elliott-Sale KJ, Dolan E, Swinton PA, Ansdell P, Goodall S, Thomas K, Hicks KM. The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. Sports Med. 2020 Oct;50(10):1813-1827. doi: 10.1007/s40279-020-01319-3. PMID 32661839
• Miller P, Robinson AL, Sparks SA, Bridge CA, Bentley DJ, McNaughton LR. The Effects of Novel Ingestion of Sodium Bicarbonate on Repeated Sprint Ability. J Strength Cond Res. 2016 Feb;30(2):561-8. doi: 10.1519/JSC.0000000000001126. PMID 26815179
• Heibel AB, Perim PHL, Oliveira LF, McNaughton LR, Saunders B. Time to Optimize Supplementation: Modifying Factors Influencing the Individual Responses to Extracellular Buffering Agents. Front Nutr. 2018 May 8;5:35. doi: 10.3389/fnut.2018.00035. eCollection 2018. PMID 29868599
• McNaughton LR. Sodium citrate and anaerobic performance: implications of dosage. Eur J Appl Physiol Occup Physiol. 1990;61(5-6):392-7. doi: 10.1007/BF00236058. PMID 2079058
• McNaughton L, Cedaro R. Sodium citrate ingestion and its effects on maximal anaerobic exercise of different durations. Eur J Appl Physiol Occup Physiol. 1992;64(1):36-41. doi: 10.1007/BF00376437. PMID 1735409
• Urwin CS, Snow RJ, Orellana L, Condo D, Wadley GD, Carr AJ. Does varying the ingestion period of sodium citrate influence blood alkalosis and gastrointestinal symptoms? PLoS One. 2021 May 17;16(5):e0251808. doi: 10.1371/journal.pone.0251808. eCollection 2021. PMID 33999939

Identifiers

NCT: NCT07737327 · SBA 25/791 · 225S791

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗