About this trial
This randomized, double-blind, placebo-controlled crossover study will investigate whether acute betaine ingestion as part of a pre-exercise hyperhydration strategy improves endurance running performance and influences hydration-related responses during prolonged exercise.
Approximately 30 recreationally trained male and premenopausal female runners will complete two experimental trials: a betaine condition and a placebo/control condition. In the betaine condition, participants will ingest anhydrous betaine at a dose of 0.07 g/kg body mass as part of a standardized pre-exercise hydration protocol providing a total fluid intake of approximately 25 mL/kg body mass.
Following the hydration protocol, participants will complete 60 minutes of treadmill running at 60% of the running velocity corresponding to VO₂max, followed by a 5-minute recovery period and a 5-km treadmill time trial.
The primary outcome will be 5-km running time-trial performance. Secondary outcomes will include exercise-induced fluid and sweat loss, urinary hydration markers, sweat electrolyte concentrations, physiological responses, exercise economy, substrate utilization, blood lactate concentration, perceived exertion, thirst, and thermal sensation.
Eligibility criteria
This trial accepts healthy volunteersQualifiers
Age 18-45 years
Sex: men and premenopausal women
Continuous running training for at least 12 months
At least 3 running training sessions per week
Disqualifiers
Age <18 or >45 years
Postmenopausal women
Use of betaine, choline, folic acid/folate, or vitamin B12 supplements within 3 months prior to study participation
Current musculoskeletal injury or injury occurring within the previous 2 months
Trial design
Crossover
Treatments tested in this trial
Anhydrous Betaine
Dietary supplementAnhydrous betaine (trimethylglycine) will be administered as a single dose of 0.07 g/kg body mass, dissolved in a commercially available sports drink (5 mL/kg body mass), 150 minutes before exercise. The betaine-containing drink will constitute the first bolus of a standardized pre-exercise hyperhydration protocol providing a total fluid intake of approximately 25 mL/kg body mass over 120 minutes.
Placebo
Other interventionParticipants will receive the same commercially available sports drink (5 mL/kg body mass) without added betaine 150 minutes before exercise. This will be followed by four additional fluid boluses of mineral water (5 mL/kg each) administered at 120, 90, 60, and 30 minutes before exercise, for a total pre-exercise fluid intake of approximately 25 mL/kg body mass.
Treatment groups
Trial outcomes
Primary outcomes
5-km Running Time-Trial Performance
Time required to complete a 5-km treadmill running time trial, expressed in seconds. Participants will be instructed to complete the distance as quickly as possible and will be allowed to adjust treadmill speed throughout the trial. Lower completion time indicates better performance.
Secondary outcomes
Sweat rate
Whole-body sweat rate will be estimated from the change in body mass from immediately before exercise to completion of the 5-km time trial, adjusted for fluid intake and urine output, if applicable, and expressed as L/h. Body mass will be measured using the calibrated electronic scale integrated with the BOD POD system (COSMED, Italy) and expressed in kilograms (kg). Changes in body mass will also be calculated and reported as a percentage of pre-exercise body mass (%).
Other outcomes
Sweat sodium concentration
Sodium concentration will be measured in sweat samples collected from standardized sites on the forearm and thigh during exercise. Sweat samples will be collected between minutes 30 and 60 of the 60-minute running preload. Sodium concentration will be analyzed using a HORIBA ion-selective electrode analyzer and reported in mmol/L.
Sweat Potassium Concentration
Potassium concentration will be measured in sweat samples collected from standardized sites on the forearm and thigh during exercise. Sweat samples will be collected between minutes 30 and 60 of the 60-minute running preload. Sweat potassium concentration will be analyzed using a HORIBA ion-selective electrode analyzer and reported in mmol/L.
Blood lactate concentration
Blood lactate concentration will be measured using a portable Lactate Scout 4 analyzer. Measurements will be obtained immediately after completion of the 60-minute running preload and immediately after completion of the subsequent 5-km time trial. Blood lactate concentration will be reported in mmol/L.
Heart rate
Heart rate will be monitored continuously using a Garmin chest-strap heart rate monitor with integrated electrodes throughout the 60-minute running preload and the subsequent 5-km time trial. Outcome variables will include mean heart rate during the 60-minute preload, mean heart rate during the 5-km time trial, and maximal heart rate achieved during the 5-km time trial. Heart rate will be reported in beats per minute (bpm).
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