Glycogen Storage Calculator
Estimate your total glycogen storage capacity — muscle + liver — and understand how long your fuel stores last during exercise at different intensities.
Glycogen Storage Calculator
Muscle & liver glycogen capacity
Muscle glycogen capacity: ~15 g/kg lean muscle mass (untrained) to ~30 g/kg (elite). Liver: 70–120 g. Training increases GLUT4 and glycogen synthase activity, substantially raising total storage capacity.
Glycogen Depletion by Exercise Intensity
| Intensity | Energy Source | Glycogen lasts |
|---|---|---|
| Light (<50% VO2max) | Mostly fat | 4–6+ hours |
| Moderate (60–70%) | 50% fat / 50% glycogen | 90–150 min |
| High (75–85%) | Mostly glycogen | 60–90 min |
| Near-max (>90%) | Almost all glycogen | 20–45 min |
Understanding Glycogen: Your Muscles' Primary Fuel Source
Glycogen is the stored form of glucose in muscle tissue and the liver, and it is the dominant fuel source for high-intensity exercise. Muscle glycogen is stored locally within each muscle fiber and cannot be shared between muscles — your quadricep glycogen cannot be used by your bicep. Total glycogen storage capacity in a trained athlete is approximately 400–700 grams (1,600–2,800 kcal) across all muscle tissue and the liver combined, with significant variation based on muscle mass and carbohydrate availability.
Glycogen depletion is the primary cause of the "bonk" in endurance sports — the sudden performance collapse that occurs when muscle glycogen stores empty. During resistance training, glycogen is the dominant fuel for all sets lasting more than a few seconds (anything beyond pure ATP-PCr power output). Studies show that a single heavy lower-body resistance training session can deplete quadricep glycogen by 30–40%. A full-body high-volume session can deplete 40–60% of total stored glycogen, which is why post-workout carbohydrate intake within 2–4 hours is critical for next-session performance.
Glycogen resynthesis rate after exercise is approximately 5–7% per hour under optimal conditions — meaning full repletion of significantly depleted stores takes 20–24 hours even with aggressive carbohydrate intake. Consuming fast-digesting carbohydrates (white rice, fruit, sports drinks) immediately post-workout maximizes the early resynthesis window when GLUT4 transporters and glycogen synthase enzyme activity are elevated. Protein co-ingestion further enhances glycogen storage by stimulating insulin and improving amino acid-driven glycogen synthase activation. This calculator estimates how much glycogen you've used in a session to guide your post-workout carbohydrate strategy.
Glycogen and Carbohydrate Intake
1 g of glycogen stores with ~3–4 g of water. Full glycogen repletion after heavy training requires roughly your total capacity in grams of carbohydrates, consumed over 24 hours. Post-workout, 1–1.2 g carbs/kg within 30 minutes maximizes early resynthesis rate.