Carbohydrate Intolerance, Endurance Cycling Performance, Exercise, Sport Nutrition
Conditions
Keywords
13C-glucose, cycling exercise, endurance performance, carbohydrate, substrate oxidation
Brief summary
The goal of this clinical trial is to learn whether maple syrup can be used as a natural carbohydrate source to help trained male cyclists perform better during long-duration cycling. The study also aims to learn how different amounts of maple syrup affect energy use in the body, stomach comfort, and feelings of effort and fatigue. The main questions the study aims to answer are: * Does consuming more carbohydrate from maple syrup help participants finish a 20-kilometer cycling time trial faster? * How do different amounts of maple syrup change how the body uses carbohydrates and fats during long exercise? * Are higher amounts of maple syrup easy for participants to tolerate without stomach problems? Researchers will compare four drinks: 1. A placebo drink (a look-alike drink with no calories), 2. A drink that provides 60 grams of carbohydrate per hour, 3. A drink that provides 90 grams per hour, and 4. A drink that provides 120 grams per hour. They will compare these drinks to see whether higher carbohydrate amounts lead to better cycling performance and how each dose affects comfort and metabolism. Participants will: * Attend a screening visit that includes a health check and a glucose tolerance test. * Complete a fitness test to measure their aerobic capacity and practice the cycling tests used in the study. * Take part in four separate exercise sessions in random order. Each session includes: * Drinking one of the four study beverages during 2 hours of steady cycling, * Completing two short, all-out 6-second sprints during the ride, * Completing a 20-kilometer cycling time trial as fast as possible, * Reporting stomach symptoms and perceptions of effort, * Providing breath, blood, urine, and sweat samples so researchers can measure how their body uses fuel. All drinks will look, taste, and smell similar so participants cannot tell which one they are receiving. Meals before each session will be provided to keep conditions the same across visits. This study may help athletes and active people choose natural carbohydrate sources that support both performance and comfort during long endurance exercise. The findings may also guide future research on the use of maple syrup as a sports nutrition option.
Interventions
DIETARY_SUPPLEMENTMaple Syrup Beverages
Pure maple syrup is diluted in water and mixed with electrolytes (sodium, potassium, magnesium) to resemble a sports drink. Participants receive one of three carbohydrate doses (60, 90, or 120 g per hour). Drinks are ingested every 15 minutes during 120 minutes of cycling, for a total of \~750 mL per hour. All doses have the same volume, temperature, electrolyte content, and schedule.
DIETARY_SUPPLEMENTplacebo beverage
Participants receive a calorie-free electrolyte drink designed to mimic maple syrup. Sotolon (maple aroma) and stevia are added in small amounts to reproduce sweetness, flavor, and smell without providing energy. The drink is administered in identical volumes and timing to the maple syrup beverages (\~750 mL per hour, every 15 minutes).
OTHERPre-Trial Meals
To control nutrition before each trial, participants are provided with a standardized dinner the night before and a standardized breakfast 2-3 hours before testing. Meals contain the same calories and macronutrient distribution across all sessions. Participants must also replicate their training during the previous 48 hours.
PROCEDURED₂O Fluid Absorption
At 30 minutes of cycling, participants ingest a small, safe dose of deuterium oxide (7-8 mL) to measure fluid absorption and gastric emptying. Additional blood samples are collected at +32, +35, and +40 minutes to capture early absorption. Urine is collected to measure deuterium enrichment and validate absorption kinetics.
BEHAVIORALTime Trial Performance
After 120 minutes of steady cycling, participants complete a 20-km self-paced time trial. Only distance is displayed. The primary outcome is completion time; mean power is analyzed as supportive information.
PROCEDURESubstrate Oxidation
Energy metabolism is measured using indirect calorimetry and ¹³C-sucrose breath enrichment. Samples are collected at rest and every 30 minutes during exercise to quantify carbohydrate and fat use, distinguishing ingested vs. stored carbohydrate oxidation. Urine and sweat correct protein oxidation.
PROCEDUREBlood Metabolites
Blood samples collected every 30 minutes measure glucose, insulin, lactate, and fatty acids. Samples are stored for later analysis of hormonal and metabolic responses.
DIAGNOSTIC_TESTGastrointestinal Symptoms
Participants rate stomach symptoms (0-10 scale) before exercise, every 30 minutes during cycling, and after the time trial. Scores quantify total, upper, and lower GI discomfort.
DIAGNOSTIC_TESTPerceptual Responses
Effort and muscle pain are assessed using the Borg CR100 scale during exercise and throughout the time trial at preset intervals.
DIAGNOSTIC_TESTNeuromuscular Fatigue
Participants perform two 6-second maximal sprints at baseline, 60 and 120 minutes of cycling, and after the time trial. Peak power, cadence, and torque assess fatigue progression and recovery.
OTHERHedonic Ratings
Immediately post-exercise, a 0-100 mm scale evaluates sweetness, flavor intensity, and overall liking to assess palatability of each drink.
OTHERBlinding Integrity
Bang's Blinding Index is calculated from participant guesses of drink identity to confirm whether blinding was successful.
Sponsors
Université de Montréal
Natural Sciences and Engineering Research Council, Canada
Montreal Heart Institute
Mitacs
Quebec Maple Syrup Producers
Quebec Cycling Federation
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Intervention model description
This is a randomized, double-blind, placebo-controlled, crossover trial designed to maximize statistical power. Each participant will serve as their own control, completing four experimental conditions in computer-randomized order.
Eligibility
Sex/Gender
MALE
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Age: 18-45 years. * Relative VO2max: \>55 mL·min-¹·kg-¹ for level 3; \>65 mL·min-¹·kg-¹ for level 4. * Peak Power Output (PPO): \>4.6 W·kg-¹ (absolute PPO \>320 W). * Training History: \>5 hours/week of cycling-specific training; \>1 year of consistent endurance training. * No history of metabolic disorders, gastrointestinal issues, or contraindications to exercise testing.
Exclusion criteria
* Current or past metabolic disorders (diabetes, metabolic syndrome) * Cardiovascular disease or abnormal ECG at rest * Gastrointestinal disorders (IBS, Crohn's, celiac disease) * Food allergies or intolerances (particularly maple, fructose) * Current use of medications affecting metabolism * Smoking or nicotine use * Alcohol consumption \>14 units/week * Recent illness or injury (\<4 weeks) * Participation in other clinical trials (\<3 months) * Unable to maintain consistent training during study period
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Assess the dose-response effect of maple syrup carbohydrate ingestion (0, 60, 90, 120 g·h-¹) on 20-km cycling time-trial performance in trained male cyclists. | Immediately after completion of the 20-km time trial during each experimental visit | 20-km time trial completion time (minutes), measured at the end of each experimental visit. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Substrate oxidation rates during exercise | At rest, immediately before exercise, and every 30 minutes during 120 minutes of constant-load cycling | Exogenous and endogenous carbohydrate oxidation, fat oxidation, and protein oxidation rates (g·min-¹) measured via ¹³C stable isotope breath enrichment and indirect calorimetry. |
| Plasma metabolite concentrations | Measured before beverage ingestion, immediately pre-exercise, every 30 minutes during the 120-minute constant-load cycling, and immediately post-exercise (before the time trial). | Plasma glucose, insulin, lactate, and free fatty acid concentrations sampled before beverage ingestion, pre-exercise, every 30 minutes during constant-load exercise, and immediately after. |
| Ratings of perceived effort during exercise | Assessed 3 minutes after exercise begins; every 30 minutes during the constant-load cycling (30, 60, 90, 120 min); and at approximately 126, 127, 130, 136, and 145 minutes (corresponding to 0.5, 5, 10, 15, and 20 km during the time trial) | Ratings of perceived effort (CR100 scale, 0-100) collected after 3 minutes and every 30 minutes during constant-load exercise, and during the time trial. |
| Assess gastrointestinal tolerance and symptoms across maple syrup doses and placebo. | Measured pre-exercise; every 30 minutes during the 120-minute constant-load cycling (30, 60, 90, 120 min); and immediately after the time trial. | Gastrointestinal distress scores (0-10 on a modified visual analog scale, mVAS), rated pre-exercise, every 30 minutes during the constant-load exercise, and post-TT; includes composite scores for total, upper, and lower GI symptoms. |
| Peak power output during maximal sprints | Baseline, 60 minutes, 120 minutes, and immediately after time trial | Peak power output (watts) from two 6-second maximal sprints performed at baseline, 60 minutes, 120 minutes, and post-time trial. |
| Mean power output during 20-km time trial | Approximately 25-30 minutes (continuously recorded during the 20-km time trial) | Mean power output (watts) recorded continuously during the 20-km time trial. |
Countries
Canada
Contacts
CONTACTPhilippe Parent, BSc
PRINCIPAL_INVESTIGATORJonathan Tremblay, PhD
Université de Montréal
Outcome results
None listed