Exercise-Induced Fatigue, Athletic Performance, Soccer
Conditions
Keywords
Sodium citrate, Buffering agent, Repeated sprint performance, Female athletes, Soccer, Anaerobic performance, Blood bicarbonate, Individualized timing
Brief summary
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
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.
Sodium chloride (NaCl) at a taste-matched dose dissolved in flavored water, ingested orally. Exercise begins 120-150 minutes post-ingestion.
Sponsors
Study design
Masking description
The lead researcher managed randomization and was not involved in blood sampling or performance testing. Participants and the blood-sampling investigator were blinded to treatment allocation.
Intervention model description
Each participant will complete both the sodium citrate and placebo trials in a randomized order, with a washout period of at least three days between trials.
Eligibility
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Minimum Power | 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) | The lowest power output recorded across six maximal 35-meter sprints during the Running-based Anaerobic Sprint Test (RAST). Calculated as body weight (kg) multiplied by the square of sprint distance (m) divided by the cube of the slowest sprint time (s). |
| Fatigue Index | 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) | The rate of power decline across six maximal 35-meter sprints during the Running-based Anaerobic Sprint Test (RAST). Calculated as the difference between peak power and minimum power divided by total sprint time (W/s). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Peak Power | 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) | The highest power output recorded across six maximal 35-meter sprints during the Running-based Anaerobic Sprint Test (RAST). Calculated as body weight (kg) multiplied by the square of sprint distance (m) divided by the cube of the fastest sprint time (s). |
| Mean Power | 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) | The average power output recorded across six maximal 35-meter sprints during the Running-based Anaerobic Sprint Test (RAST). Calculated as the mean of all six individual sprint power values. |
| Sprint Times | 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) | Individual sprint times recorded for each of the six maximal 35-meter sprints during the Running-based Anaerobic Sprint Test (RAST), measured in seconds using a photoelectric timing system. |
| Blood Bicarbonate Concentration | 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. | Capillary blood bicarbonate concentration (HCO₃-, mmol/L) measured at baseline, pre-exercise, and post-exercise using a portable blood gas analyzer. |
| Blood pH | 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. | Capillary blood pH measured at baseline, pre-exercise, and post-exercise using a portable blood gas analyzer. |
| Blood Lactate Concentration | 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. | Capillary blood pH measured at baseline, pre-exercise, and post-exercise using a portable blood gas analyzer. |
| Rating of Perceived Exertion (RPE) | 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) | Perceived exertion rated by participants after each of the six maximal 35-meter sprints using the Borg RPE scale (6-20). |
Contacts
Hacettepe University, Faculty of Sport Sciences
Hacettepe University