💬In plain words
What the trial is, and whether it could suit you
This study will examine how three commonly used pre-run nutritional supplements-caffeine, L-citrulline, and an exogenous ketone supplement-affect physiological and perceptual responses during a fixed-pace 5 km treadmill run in healthy, physically active runners.
Participants will complete one screening and baseline visit followed by four experimental visits in a randomized order. At each experimental visit, participants will receive caffeine, L-citrulline, an exogenous ketone supplement, or placebo before completing a fixed-pace 5 km treadmill run. Each participant will receive all four conditions and will therefore serve as their own control.
The study will evaluate measures including running economy, heart-rate responses, oxygen consumption, respiratory measures, blood lactate and ketone concentrations, perceived exertion, gastrointestinal symptoms, fatigue, energy, and focus. A rand
Sign in to get the eligibility rules as simple questions to take to your doctor.
📋 Eligibility rules (as published)
Inclusion Criteria:
* Age 18-35 years
* Healthy adult
* Able to provide written informed consent
* Regularly engaged in running-based aerobic training at least 3 times per week for at least 30 minutes per session during the past 3 months
* Able to complete a 5 km run in under 30 minutes
* Able and willing to comply with treadmill testing, fingerstick testing, dietary standardization, supplement restrictions, and pre-visit instructions
* Participants randomly selected for the continuous glucose monitoring subgroup must also be willing to undergo Dexcom Stelo continuous glucose monitor placement and wear
Exclusion Criteria:
* Known cardiovascular, metabolic, pulmonary, or neurological disease that may increase the risk associated with exercise testing or materially influence study outcomes
* Uncontrolled hypertension or another cardiovascular condition that, in the investigator's judgment, makes vigorous treadmill exercise unsafe
* Diagnosed type 1 or type 2 diabetes mellitus or another known metabolic disease that may materially influence study outcomes
* Pregnant, breastfeeding, or planning pregnancy during the study period
* Current use of nitrate medications or phosphodiesterase type 5 (PDE5) inhibitors, including sildenafil, tadalafil, or vardenafil
* Known sensitivity or allergy to caffeine, L-citrulline, exogenous ketone/BHB salt products, or any study beverage ingredient
* Current use of stimulant medications or other medications that may significantly influence cardiovascular, blood pressure, or metabolic responses to exercise, as determined by the investigator
* Musculoskeletal injury or condition that limits safe treadmill running
* Smoking or regular use of nicotine products
* Recent illness, surgery, or hospitalization that, in the opinion of the investigators, may interfere with safe participation or study outcomes
* Unable or unwilling to comply with study procedures or pre-visit standardization requirements
* Running fewer than 3 times per week or otherwise not meeting the running-training inclusion criterion
💊
What it tests
- Caffeine
- L-Citrulline
- Exogenous Ketone (Beta-Hydroxybutyrate)
- placebo beverage
Saint Louis University, Allied Health Building
St Louis, United States
🤝 Taking part is your choice, and you can leave at any time. Only the trial team can confirm you are eligible — always decide together with your own doctor.
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