Muscle Glycogen Depletion Simulator - Predict The Exact "Wall" Kilometer
Calculate hourly carbohydrate burn at your marathon pace and plan gel consumption to avoid hitting the wall at km 32.
How to Use Glycogen & Bonk Simulator in 3 Simple Steps
Step 1: Upload
Drag & drop your .FIT, .GPX, or .TCX activity file. All processing is 100% private in your browser.
Step 2: Process
FitCrop inspects telemetry streams, removes anomalies, recalibrates metrics, or fixes binary checksums.
Step 3: Export
Download your clean Strava, Garmin, and Zwift compatible file with 1 click. Zero server wait.
Frequently Asked Questions
Why do marathoners hit the wall at kilometer 32 (mile 20)?
Human muscle and liver stores hold ~450g of glycogen (1,800 kcal). Without exogenous carbohydrate intake, this internal reservoir is exhausted after ~2 hours of Zone 3 running.
How many grams of carbs per hour should I consume?
Elite endurance guidelines recommend 60g to 90g of carbohydrates per hour using 1:0.8 glucose-to-fructose ratios.