Gut Training Protocol Generator

A personalized carbohydrate intake optimization calculator for endurance athletes. Built with Next.js 15, TypeScript, and Tailwind CSS.

🎯 What This Tool Does

1. Questionnaire (6 questions, ~60 seconds): Collects athlete profile
2. Opportunity Assessment: Calculates personalized time savings estimate
3. Protocol Generation (optional): Week-by-week gut training plan

🔬 Key Innovation: GI Dual Effect

GI issues have TWO distinct effects:

1. Bigger Opportunity (Time Calculation)

   • Multiplier: 1.3× if GI >30%
   • Athletes with GI issues are underabsorbing → fixing tolerance unlocks MORE gains

2. Longer Timeline (Protocol Calculation)

   • Multiplier: 1.0-1.6× based on severity
   • Building tolerance takes time → slower progression for safety

🏗️ Tech Stack

• Framework: Next.js 15 (App Router)
• Language: TypeScript
• Styling: Tailwind CSS v4
• Deployment: Vercel-ready
• Dependencies: Zero external dependencies (pure React)

🚀 Getting Started

# Install dependencies
npm install

# Run development server
npm run dev

# Build for production
npm run build

# Run validation tests
npx tsx src/lib/validation.test.ts

Open http://localhost:3000 to view the application.

📊 Validation Tests

The calculator includes 5 validation scenarios per specification:

Test	Profile	Expected
1	Male, 70.3, 5:00, 65g/h, 5% GI	Target 90g, Save 4-7 min, 8 weeks
2	Male, 70.3, 5:00, 65g/h, 40% GI	Target 90g, Save 5-9 min, 11 weeks
3	Female, Marathon, 4:30, 35g/h, 20% GI	Target 60g (NOT 90!), Save 4-7 min
4	Male, Ironman, 11:00, 95g/h, 5% GI	Target 120g, Save 0-10 min, 8 weeks
5	Female, 100k, 12:00, 45g/h, 55% GI	Target 60g, Save 10-16 min, 17 weeks

Run tests: npx tsx src/lib/validation.test.ts

📁 Project Structure

src/
├── app/
│   ├── page.tsx          # Main entry point
│   ├── layout.tsx        # Root layout
│   └── globals.css       # Global styles
├── components/
│   ├── GutTrainerApp.tsx # Main app component
│   └── screens/
│       ├── LandingScreen.tsx
│       ├── QuestionnaireScreen.tsx
│       ├── ResultsScreen.tsx
│       ├── ProtocolSetupScreen.tsx
│       └── ProtocolResultsScreen.tsx
└── lib/
    ├── types.ts          # TypeScript types
    ├── calculations.ts   # Core calculation engine
    ├── store.ts          # State management
    └── validation.test.ts # Validation tests

🧮 Calculation Formulas

Time Savings (9 steps)

1. carb_gap = target - current
2. base_rate = 0.7% (≤90g) or 0.25% (120g)
3. base_improvement = (carb_gap / 10) × base_rate
4. gender_modifier = 0.95 (female) or 1.0
5. duration_modifier = 1.0 (<6h), 1.2 (6-8h), 1.4 (8+h)
6. gi_modifier = 1.3 (>30%) or 1.0 ⭐
7. time_saved = finish_time × all_modifiers
8. variance = 0.25 (≤90g) or 0.8 (120g)
9. range = time_saved × (1±variance), floor at 0

Protocol Length (5 steps)

1. base_weeks = 5 (4-6wk), 8 (6-10wk), 12 (10+wk)
2. gi_time_modifier = 1.0-1.6× ⭐
3. gap_modifier = 0.9-1.4×
4. total_weeks = base × gi_time × gap
5. weekly_increase = carb_gap / total_weeks

🎨 Design Principles

• Dark theme with amber/orange accents
• Mobile-first responsive design
• Transparency: Show all calculation factors
• Encouragement: Positive framing for all athletes
• Honesty: Range width indicates confidence

🔧 Shopify Integration

This is a standalone service that can be integrated with Shopify via:

• Iframe embed: Embed directly in a Shopify page
• External link: Link from your Shopify store to the Vercel deployment
• Custom app: Build a Shopify app wrapper if needed

📚 Based On Research

• Costa et al. (2017): 5.2% performance improvement
• Stellingwerff & Cox (2014): 2-3% time gains documented
• Viribay et al. (2020): Recovery benefits at 120g/h
• Urdampilleta et al. (2020): Neuromuscular function preservation

📝 License

MIT

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Built with evidence-based specifications for endurance athletes.