Scientific Basis
& Methodology

The Fuel Calculator in SUPLiR is based on current, evidence-based guidelines in sports nutrition and calculates carbohydrate targets individually from physiological profile data. This page documents the underlying algorithms and scientific references.

1. Calculation Methods Fuel Engine v4

The algorithm automatically selects the most precise available method based on the user's profile:

Method 1: FTP-Based (Cycling)

When an FTP (Functional Threshold Power) value is provided, the engine calculates actual energy expenditure per hour from watts and mechanical efficiency:

Method 2: VO2max Estimation

Without an FTP value but with VO2max available, the engine estimates an effective FTP:

Method 3: Pace-Based (Running)

For running, energy expenditure is derived from the 10km personal best — a validated proxy for the aerobic threshold:

Method 4: Table Values (Fallback)

Without profile data, the algorithm uses conservative table values based on duration and intensity level (low / medium / high).

2. Intensity Zones & Carbohydrate Ratio

The proportion of carbohydrates in total energy expenditure (carbRatio) increases with relative intensity (watts/FTP). This reflects the physiological crossover concept, where glycogen progressively replaces fat oxidation as the primary substrate at higher intensities.

Zone	Relative Intensity	Max. External Recommendation	Physiological Background
Z1 / Z2	≤ 70% FTP	75 g/h	Fat oxidation dominates; high external carb intake not absorbable
Z3	71 – 82% FTP	90 g/h	Crossover zone; mixed substrate utilisation
Z4+	> 82% FTP	User limit (carbCap)	Carbohydrates dominate; maximum intestinal capacity is the limiting factor

3. Individual Gut Tolerance (carbCap)

Since gastrointestinal absorption rates vary individually and can be trained, SUPLiR allows configuration of a personal upper limit (carbCap). The default value is 60 g/h. Athletes with well-adapted gut function can increase this up to 120 g/h.

Scientific basis: The SGLT1 transporter absorbs glucose at a maximum rate of approx. 60 g/h. For higher absorption rates, research recommends combining glucose (maltodextrin) and fructose at a 2:1 ratio, additionally utilising the GLUT5 transporter to maximise absorption and minimise gastrointestinal distress.

4. Caffeine System

SUPLiR calculates a personalised daily caffeine limit and distributes caffeinated products in the plan according to evidence-based timing guidelines:

• Personalised limit: Default 3 mg/kg body weight, maximum 400 mg/day (WHO recommendation for healthy adults). The limit can be manually overridden.
• Timing logic: Caffeinated products are scheduled no earlier than minute 45, as peak effect occurs approximately 60 minutes after ingestion.
• Warnings: A warning appears in the planner at 80% of the daily limit; once the limit is reached, no further caffeinated products are scheduled.

5. Carbohydrate Intake by Duration

Regardless of calculation method, the following thresholds apply:

• < 45 min: No external fueling required; glycogen stores sufficient.
• 45 – 59 min (high intensity only): 60 g/h (e.g. criterium racing / interval training). Mouth rinsing can be an alternative for very short sessions.
• 60 – 150 min: 30 – 90 g/h depending on intensity and profile.
• > 150 min: Up to carbCap (max. 120 g/h) at high intensity with a trained gut.

6. Recovery

Following exercise, the algorithm recommends approximately 1.0 – 1.2 g of carbohydrates per kg of body weight, combined with 20 – 30 g of protein to support muscle protein synthesis. Product selection is drawn from the user's inventory and prioritises items tagged usage: "post".