Calculation Details & Scientific Methodology

Base Rate by Duration (Jeukendrup 2014 Guidelines):

• < 45-60 min: Minimal/no intake needed (mouth-rinse may help)
• 45-90 min: 30-40 g/hr
• 1.5-2.5 hrs: 60 g/hr
• > 2.5 hrs: Up to 90 g/hr (requires 2:1 glucose:fructose)

Note: With substantial gut training and 1:0.8 glucose:fructose mixes, some athletes can tolerate 100-120 g/hr (emerging research, not universal recommendation).

Intensity Multipliers (House Heuristics - Not from Research):

• 90-100% HR max: × 1.3
• 80-90% HR max: × 1.15
• 70-80% HR max: × 1.0
• 60-70% HR max: × 0.85

These intensity multipliers are our heuristics. There is evidence that higher intensity increases carb oxidation, but fixed multipliers are not from Jeukendrup 2014.

GI Training Multipliers (House Heuristics - Based on Gut Training Evidence):

• Untrained: × 0.75
• Moderately Trained: × 1.0
• Highly Trained: × 1.2

Gut training can raise tolerance/oxidation capacity, but fixed multipliers are our heuristic, not from research.

Fitness Factor (House Heuristic - From VO2max Estimation):

• VO2max > 60: × 1.2
• VO2max > 50: × 1.1
• VO2max > 45: × 1.0
• VO2max > 40: × 0.95
• VO2max ≤ 40: × 0.9

Final Rate = Base × Intensity × GI × Fitness

Capped at 90 g/hr (trained gut) or 75 g/hr (others). Intensity/GI/Fitness multipliers are our heuristics to personalize recommendations - always cap by tolerance.

ACSM 2007 Position Stand states:

• Individualize fluid replacement to sweat rate
• Start exercise euhydrated
• Avoid >2% body mass loss
• Do not recommend fixed ml/kg/hr formulas

Our Calculation Approach:

If measured sweat rate is provided (preferred):

• Replace 80-100% of measured sweat rate
• Convert L/hr to ml/hr (× 1000)

If sweat rate not provided (estimated):

• Base estimate: 12 ml/kg/hr × body weight (house heuristic)
• Adjust for temperature and intensity (house heuristics)
• Use measured sweat rate whenever possible for accuracy

Safety Caps:

• Minimum: 400 ml/hr
• Maximum: 1,200 ml/hr (lowered from 2,000 ml/hr for safety)

From Baker (2017):

• Range: 10-90 mmol/L (~230-2,070 mg/L)
• Inter-individual variance is very large (3-fold differences)
• Heat acclimatization tends to lower sweat [Na⁺]

Our Approach:

• Use average ~1,000 mg/L (≈43 mmol/L) when sweat rate is known
• Individual testing is ideal - values can range 500-1,500 mg/L
• Fixed "hot vs cool" adjustments are oversimplifications

Standard Practice:

Many sports nutrition sources recommend starting with 300-600 mg Na⁺/hr during long/hot events, then adjusting based on individual needs and sweat loss.

Our Duration-Based Replacement Factors (House Heuristic):

• < 2 hrs: 60% replacement
• 2-3 hrs: 70% replacement
• 3-4 hrs: 80% replacement
• 4-6 hrs: 90% replacement
• > 6 hrs: 100% replacement

These duration-based factors are our heuristic, not from standard guidelines. In practice, replace sodium proportionally to fluid replacement and adjust based on individual testing.

Normal Whole-Body Glycogen:

• ~500-600 g total (~500 g muscle + ~100 g liver in average-sized adults)
• Can increase substantially with proper loading

Standard Loading Protocol (Research-Based):

• 10-12 g carbohydrate per kg body weight per day
• For 36-48 hours before events >90 minutes
• Preceded by glycogen depletion/taper (optional, varies by protocol)

Example (70 kg athlete):

10-12 g/kg/day × 70 kg = 700-840 g carbs/day for 36-48 hours

Our Body-Weight Bin Approach (Simplified Heuristic):

• Base estimates range 350-550 g depending on body size
• Supercompensation can reach 500-900 g total
• Loading protocols vary by race duration

For precise recommendations, use g/kg/day protocol (10-12 g/kg/day).

⚠️ The following formulas are house heuristics, not validated science.

Flexibility Score (Proprietary):

Score = (VO2max / 60) × 50 + (Fat oxidation rate / 0.8) × 50

Fat Oxidation Rate Estimate (Heuristic):

Fat rate (g/hr) = VO2max × 0.015 × body weight (kg)

Note: This equation has unit issues and is not from peer-reviewed sources.

Carb Oxidation Rate:

Estimated from total energy need minus fat oxidation

Interpretation (Proprietary Scale):

• 80-100: Excellent (elite level)
• 60-79: Good (highly trained)
• 40-59: Moderate (trained)
• < 40: Needs improvement

For accurate assessment: Use measured FATmax (maximum fat oxidation rate) and MFO (maximum fat oxidation) from indirect calorimetry testing in a lab setting.