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Completed

NCT Number: NCT06965491

The Effects of Exogenous Ketosis on Ultra-endurance Recovery and Performance

The study aims to investigate the effects of post-exercise and pre-sleep ketosis via oral ketone ester supplementation on physical and mental recovery during a multi-day cycling stage race.

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Key information

Conditions

Exogenous Ketosis Behavior Behavioral Symptoms Endurance Cycling Performance Fatigue Fatigue, Mental Fatigue; Muscle, Heart Mental Fatigue Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–59 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

KU Leuven

Leuven, Vlaams-Brabant, 3000, Belgium

About this study

Ultra-endurance events are becoming increasing popular. Participation in the multi-day events adds a lot of physical and mental strain on the body, while the athletes are still required to perform. Without appropriate recovery the athletes are at increased risk of overreaching, injury, or illness.

Therefore, the purpose of the study is to create a better understanding of the exercise fatigue experienced during ultra-endurance performance and the role intermittent exogenous ketosis (IEK) plays in reducing the amount of fatigue to maintain performance during multi-day racing and lower the risk of injury and illness.

Participants will first compete in a 8-day simulated stage race performed on taxc trainers and then we will conduct a field study during the Absa Cape Epic a 8-day mountain bike stage race. Immediately following each stage and 30-mins before bed the participants will consume either a ketone ester and taste-match placebo drink. During the race the following variables will be measured; hydration status, weight change, activity readiness, and nutrition intake. Cognitive function will be assessed on day 2, 4 and 8 of racing. One day before and one day after the race the participants will report to the lab to assess basal metabolic rate, stress via questionnaires, appetite, cognitive function, muscle biopsies, venous blood samples, mechanical efficiency and 30-min Time Trial.

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • have been cycling consistently for at least 1 year before entry into the study
  • have been cycling for a minimum of 7 hours per week for the 6 months leading up to the study
  • additional for the field study: valid entry to the 2025 edition of the Absa Cape Epic
  • non-smoker

Exclusion criteria

  • Do not follow a ketogenic diet or low-carbohydrate diet
  • Have any metabolic or auto-immune disease that will influence their metabolism
  • Take medication or supplements that is known to affect ketone supplement metabolism
  • suffering from a recurring injury or illness from which they have not fully recovered that is a contr-indication to perform high-intensity exercise
  • Unable to finish each stage
  • Women: if they are pregnant or breastfeeding

Treatment and study plan

Placebo supplement

Dietary Supplement

Placebo supplement:

Oral supplement containing: 16.4 grams of medium chained triglycerides, 1mM or sucrose octaacetate and water

Ketone Ester Supplement

Dietary Supplement

Ketone ester supplement Oral supplement containing: 25 grams of pure (R)-3-hydroxybutyl-(R)-3-hydroxybutyrate ketone monoester drink

Primary outcomes

  1. Muscle soreness

    Time frame: During the intervention

    Visual analog scale (0-10) How sore does you leg muscles feel? The VAS was used as a subjective measure of muscle soreness

  2. Physical stress

    Time frame: pre-intervention and 1 day after the intervention

    RESTQ-76 sport questionnaire was used to assess the stress-recovery balance

  3. Hydration status

    Time frame: Baseline, During the intervention and 1 day after the intervention

    Before every stage, the participants provided a urine sample in a cup. A urine-specific refractometer (Atago) was used to determine their hydration status

  4. Cognitive function: reaction time

    Time frame: Pre-intervention, day 2, 4 and 8 of the intervention

    CANTAB test battery reaction time test was used to determine reaction time in milliseconds.

  5. Cognitive function: rapid visual processing

    Time frame: Pre-intervention, day 2, 4 and 8 of the intervention

    CANTAB test battery rapid visual processing test was used to assess their susceptibility to false alarms

  6. Cognitive function: swm

    Time frame: Pre-intervention, day 2, 4 and 8 of the intervention

    CANTAB spatial working memory test was used to access executive function; the main outcome measure used was the number of errors

  7. Sleep Duration

    Time frame: 1 week prior to racing and during the race

    Fitbit inspire 3 was used to measure sleep duration (hours:minutes:seconds)

  8. Sleep: REM

    Time frame: 1 week prior to racing and during the race

    The Fitbit Inspire 3 was used to measure the total duration of rapid eye motion (REM)sleep during each night for the duration of the study. The REM sleep phase will be analysed in minutes

  9. Sleep: Non-REM

    Time frame: 1 week prior to racing and during the race

    The Fitbit Inspire 3 will be used to determine the NON-REM sleep phase for each night in minutes

  10. Sleep: WASO

    Time frame: 1 week prior to racing and during the race

    The FITBIT inspire 3 will be used to measure wake after sleep onset in minutes for each night

Secondary outcomes

  1. Mechanical efficiency

    Time frame: pre-intervention and 1 day after the intervention

    Mechanical efficiency will be determined during three constant load (100 watts, 150 watts, and 200 watts) cycling bouts of 5 minutes on a calibrated ergometer (Avantronic Cyclus II). Throughout the test, gas exchange will continuously be measured using calibrated metabolic analyzer with a face mask (Cortex, Metalyzer IIIb). VO2 and VCO2 data of the final minute of each workload will be used to calculate gross efficiency (%).

  2. Time trial performance

    Time frame: pre-intervention and 1 day after the intervention

    The participants will perform a 30-minute time trial. The average power output (watts) achieved will be used as the outcome measure.

  3. Appetite

    Time frame: pre-intervention, during the intervention, 1 day after the intervention

    Appetite will be assessed with a Likert visual analog scale (0-10) using the following four questions:

    "How hungry do you feel?" "How full do you feel?" "How satisfied do you feel?" "How much do you think you could eat now?"

  4. Macronutrient intake

    Time frame: baseline, during the intervention

    Participants will complete a food diary using the Mijnetemeter application on their phone. Total fat, protein and carbohydrate intake will be determined in grams for each day.

  5. Total energy intake

    Time frame: baseline, during the intervention

    Participants will complete a food diary, using the Mijnetemeter application on their phones. total energy intake (kilojoules) will be calculated for each day.

  6. Racing intensity

    Time frame: during each stage

    hear rate zones during racing

  7. Body weight change

    Time frame: During the intervention

    Body mass was measured using a SECA, model 813 electrical scale, before and after each stage as a secondary method to assess hydration status. Body mass was measured to the nearest 0.1 kilogram

Sponsors and collaborators

Lead sponsor

KU Leuven

Other

Collaborators

  • University of Stellenbosch

Registry information

Official study title

Exploring the Role of Intermittent Exogenous Ketosis on Physical and Mental Fatigue During Ultra-endurance Performance

Important dates

Study start
2024
Primary completion
2025
Study completion
2025
First posted
May 11, 2025
Registry last updated
Feb 20, 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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