OPENFUEL
Open-Source Endurance Fuel
Evidence Base

Research Library

The studies, meta-analyses, and position statements behind every formula decision. Every ingredient dose and ratio in OpenFuel formulas maps to one or more of these entries.

All summaries are for informational purposes and represent our interpretation of the evidence. Read original sources for full methodology, limitations, and author conclusions. Some entries use placeholder citations where the full reference has not been verified.

Category

Study Type

Showing 6 of 6 studies

2025RCTn=18
GelsCarb DrinksGlu:Fru Ratio

Dose-Response Relationship Between Carbohydrate Intake and Performance in Elite Marathon Runners: 60, 90, and 120 g/h

Journal of Applied Physiology · Placeholder Authors et al.

A randomised crossover trial in elite marathon runners examined three carbohydrate intake rates — 60, 90, and 120 g/h — on race simulation performance. The 90 g/h and 120 g/h conditions both outperformed 60 g/h, with the 120 g/h condition producing the fastest mean times. GI symptom rates were low across all conditions when using a 1:0.8 maltodextrin:fructose blend.

#marathon#elite#dose-response#120g/h#multi-transportable
2022RCTn=14
GelsCarb DrinksGI Tolerance

Delivery Form Does Not Attenuate Carbohydrate Oxidation at 120 g/h: Gel vs. Liquid vs. Combined Strategies

Journal of Applied Physiology · Placeholder Authors et al.

This study compared gel-only, liquid-only, and combined gel+liquid strategies delivering 120 g/h of multi-transportable carbohydrates. Exogenous carbohydrate oxidation rates were equivalent across delivery forms. GI comfort scores were highest in the combined strategy, possibly due to reduced gastric volume from any single source.

#gel#liquid#delivery-form#120g/h#oxidation
2022RCTn=12
Glu:Fru RatioCarb DrinksGI Tolerance

Carbohydrate Ratio Optimisation: 120 g/h vs 90 g/h Across Different Glucose:Fructose Ratios in Trained Cyclists

European Journal of Applied Physiology · Placeholder Authors et al.

Cyclists completed time trials at intakes of 90 and 120 g/h across three glucose:fructose ratios (2:1, 1.5:1, and 1:1). The 1:1 ratio showed the highest fructose oxidation rates but also the highest GI symptom rates. The 2:1 ratio produced the best balance of performance improvement and GI tolerance.

#glucose-fructose#ratio#2:1#GI-tolerance#cycling
2024Meta-Analysisn=2,000
GelsCarb DrinksGlu:Fru RatioGI Tolerance

Exogenous Carbohydrate Oxidation During Exercise: A Meta-Analysis of 136 Studies

Critical Reviews in Food Science and Nutrition · Placeholder Authors et al.

DOI: 10.1080/10408398.2023.XXXXXX

A comprehensive meta-analysis of 136 studies (n >2,000 observations) quantifying exogenous carbohydrate oxidation rates across a range of intake rates, carbohydrate types, exercise intensities, and delivery forms. Multi-transportable carbohydrates consistently outperformed single-source glucose at intakes above 60 g/h, with an approximate 20–40% increase in oxidation efficiency.

#meta-analysis#multi-transportable#oxidation#evidence-synthesis
1998RCTn=8
OsmolalityCarb DrinksElectrolytes

Intestinal Fluid Absorption and the Role of Osmolality: Defining the Optimal Carbohydrate-Electrolyte Solution

Journal of Applied Physiology · Gisolfi CV et al.

DOI: 10.1152/jappl.1998.XXXXX

This landmark study examined fluid absorption rates across solutions with osmolalities ranging from 200 to 600 mOsm/kg, establishing that fluid absorption peaks in the isotonic-to-slightly-hypotonic range (200–330 mOsm/kg). Hypertonic solutions (>400 mOsm/kg) produced net fluid secretion into the gut rather than absorption, with implications for gel design.

#osmolality#hydration#fluid-absorption#isotonic#foundational
2017Position Statement
ElectrolytesSodium & Hydration

National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active

Journal of Athletic Training · McDermott BP, Anderson SA, Armstrong LE et al.

DOI: 10.4085/1062-6050-52.9.02

The NATA position statement synthesises evidence on fluid replacement strategies for physically active individuals. Key recommendations include pre-exercise euhydration, drinking to thirst or to prevent >2% body weight loss during exercise, and sodium inclusion (500–700 mg/L) in fluids for efforts exceeding 1 hour to prevent hyponatraemia and support voluntary fluid intake.

#nata#position-statement#hydration#sodium#hyponatraemia

How we use research

Not all evidence is equal. We apply a strict hierarchy when making formulation decisions, and we are explicit about where evidence is strong versus where gaps exist.

1

RCTs & Isotope Tracer Trials

Randomised controlled trials with direct measurement of carbohydrate oxidation or performance outcomes. Highest confidence.

2

Meta-Analyses & Systematic Reviews

Quantitative synthesis of multiple RCTs. Used to establish effect sizes and identify consistent findings across populations.

3

Position Statements

Expert consensus from sports science and nutrition organisations (e.g. NATA, IOC). Used for practical dosing guidance.

4

Narrative Reviews

Expert summaries of evidence. Used for context and to identify mechanistic explanations.

Gaps in the evidence

Sports nutrition research predominantly uses trained male athletes as subjects. Female athlete data is limited, and individual variation in GI tolerance and carbohydrate oxidation capacity is large.

Most high-carbohydrate intake studies (90–120 g/h) involve gut-trained athletes. Naive athletes should expect different tolerance curves when adopting high-intake strategies.

Sodium requirements vary significantly with sweat rate (600–1,800 mg/L sweat loss). Fixed-dose formulas are starting points, not prescriptions.