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Completed

NCT Number: NCT07171047

Effects of Sodium Bicarbonate on Endurance Performance

This study is investigating whether taking sodium bicarbonate, a common supplement used by endurance athletes, can improve cycling performance during prolonged exercise and in a time trial. Sodium bicarbonate may help reduce muscle acidity, which could delay fatigue and improve performance. The goal of this study is to determine if this supplement can help athletes perform better during long, intense efforts like those seen in real competitions.

Participants in this study are well-trained cyclists who will complete two exercise trials in a laboratory setting. Each trial involves three hours of moderate cycling followed by a 20-30-minute time trial at maximum effort. Before each trial, participants will take either sodium bicarbonate or a placebo.

The study will measure performance outcomes, such as time trial results, as well as physiological responses, including heart rate, oxygen use, and muscle fatigue. Researchers hope to better understand how sodium bicarbonate can help endurance athletes and provide guidelines for its use in competitive sports.

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Key information

Conditions

Healthy Athlete Performance Well-trained Athletes

Age range

16 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Red Bull Athlete Performance Center

Thalgau, State of Salzburg, 5303, Austria

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • age 16-50 years
  • well-trained cyclists
  • Proof of physical fitness (e.g. sports medical examination required) for measurements with higher intensities (e.g. endurance tests, competition simulation)
  • >10h endurance training per week

Exclusion criteria

  • Systemic disease or other known pathology in the organs: heart, lungs, kidney, stomach, spleen, liver, gall bladder, and intestines.
  • Evidence of pulmonary disease: forced expiratory volume in one second/forced expiratory volume < 70% with/without symptoms (cough, sputum) or other evidence of pulmonologic disease.

Diabetes II.

Treatment and study plan

Placebo then Verum

Dietary Supplement

Intake of 0.3 g/kg bodyweight of maltodextrin with hydrogel as placebo and 0.3 g/kg bodyweight of sodium bicarbonate with hydrogel as Verum

Verum then Placebo

Dietary Supplement

Intake of 0.3 g/kg bodyweight of maltodextrin with hydrogel as placebo and 0.3 g/kg bodyweight of sodium bicarbonate with hydrogel as Verum

Primary outcomes

  1. Endurance performance

    Time frame: 20-30 minutes, immediately after completion of the time trial for each condition (Placebo and Verum), assessed on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in time trial performance (average power in watts) between placebo and verum condition

Secondary outcomes

  1. Difference in questionnaire score - gastrointestinal symptoms

    Time frame: 6.5 hours (rest, breakfast, every 30min during 3-hour low-intensity, after TT) for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in questionnaire score gastrointestinal symptoms between placebo and verum condition (0-10, higher score indicates more severe symptoms).

  2. Difference in questionnaire score - Energy & Confidence

    Time frame: 3 hours (every 30min during 3-hour low-intensity) for each condition (Placebo and Verum), assessed on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in questionnaire score energy and confidence in time trial performance between placebo and verum condition (0-10, higher score indicates more Energy or Confidence in time trial performance).

  3. Difference in questionnaire score - rate of perceived exertion

    Time frame: 3.5 hours (every 30min during 3-hour low-intensity, after TT) for each condition (Placebo and Verum), assessed on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in questionnaire score overall and legs only perceived exertion between placebo and verum condition (0-10, higher score indicates a higher degree of perceived exertion).

  4. Difference in blood count

    Time frame: 6.5 hours (rest, every 30min during 3-hour low-intensity, after TT) for each condition (Placebo and Verum), assessed on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in capillary blood count between placebo and verum condition

  5. Difference in pH & HCO3 kinetics

    Time frame: 6.5 hours (rest, breakfast, every 30min during 3-hour low-intensity, after TT) for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in pH & HCO3 kinetics between placebo, verum and resting verum condition

  6. Difference in heart rate

    Time frame: 3.5 hours, assessed continuously (every second) during 3 hour low-intensity and TT for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in heart rate (bpm) between placebo and verum condition

  7. Difference in oxygen uptake

    Time frame: 3 hours, assessed for 5 min every 30 min during 3 hour low-intensity for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in oxygen uptake (ml/kg/min) between placebo and verum condition

  8. Difference in blood lactate concentration

    Time frame: 3.5 hours, assessed every 30 min during 3 hour low-intensity and after TT for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in blood lactate concentration (mmol/L) between placebo and verum condition.

  9. Difference in substrate utilization

    Time frame: 3 hours, assessed for 5 min every 30 min during 3 hour low-intensity for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in substrate utilization between placebo and verum condition.

  10. Difference in ventilation

    Time frame: 3 hours, assessed for 5 min every 30 min during 3 hour low-intensity for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in ventilation (L/min) between placebo and verum condition

  11. Difference in core body temperature

    Time frame: 3.5 hours, assessed continuously during 3 hour low-intensity and TT for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in core body temperature (°) between placebo and verum condition.

  12. Difference in muscle oxygenation

    Time frame: 3.5 hours, assessed continuously during 3 hour low-intensity and TT for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in muscle oxygenation (SmO2) of the vastus lateralis between placebo and verum condition.

  13. Difference in glucose level

    Time frame: 24 hours, assessed continuously for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in glucose level (mg/dl) between placebo and verum condition.

  14. Difference in sodium content

    Time frame: 3.5 hours, assessed during 3 hour low-intensity and TT for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in sodium content (mg/hr) between placebo and verum condition

  15. Difference in sweat rate

    Time frame: 3.5 hours, assessed during 3 hour low-intensity and TT for each condition (Placebo and Verum), on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in sweat rate (L/hr) between placebo and verum condition.

  16. Difference in next morning weight

    Time frame: 24 hours, assessed in the morning for each condition (Placebo and Verum) and the following day, on test day 1 and test day 2 respectively, with a washout period of 3-7 days between appointments (test days).

    Difference in weight (kg) measured in the morning of the test day and the following day (before breakfast after urination and defecation)

Sponsors and collaborators

Lead sponsor

University of Salzburg

Other

Collaborators

  • Red Bull Athlete Performance Center

Registry information

Official study title

Effects of Sodium Bicarbonate Supplementation on Endurance Performance and Physiological Responses During Simulated Cycling Competition

Acronym: SBEP

Important dates

Study start
2025
Primary completion
2025
Study completion
2025
First posted
Sep 12, 2025
Registry last updated
Mar 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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