Glycogen Repletion Time Calculator
Our hydration sports nutrition calculator computes glycogen repletion time instantly. Get accurate stats with historical comparisons and benchmarks.
Formula
Repletion Time (hrs) = Depleted Glycogen (g) / Net Repletion Rate (g/hr)
Depleted glycogen is calculated from body weight, total glycogen capacity (15 g/kg), and depletion level. Net repletion rate equals carb intake rate times absorption efficiency (70%), minus any ongoing activity drain. Meal timing delays add additional penalty hours.
Worked Examples
Example 1: Post-Marathon Glycogen Recovery
Problem: A 70 kg runner finishes a marathon with severe glycogen depletion and begins eating immediately at 1.2 g/kg/hr while resting.
Solution: Max glycogen = 70 x 15 = 1,050 g\nSevere depletion (85%) = 1,050 x 0.85 = 893 g depleted\nCarbs/hr = 70 x 1.2 = 84 g/hr\nRepletion rate = 84 x 0.7 = 59 g/hr\nNet rate (rest) = 59 g/hr\nTime to full = 893 / 59 = 15.1 hours\nTime to 50% = 893 x 0.5 / 59 = 7.6 hours\nTotal carbs needed = 893 g
Result: 15.1 hrs to full recovery | 7.6 hrs to 50% | Need 893g carbs over ~6 meals
Example 2: Between Training Sessions Recovery
Problem: A 60 kg cyclist has 6 hours between sessions with moderate depletion, eating at 1.0 g/kg/hr starting 30 minutes after.
Solution: Max glycogen = 60 x 15 = 900 g\nModerate depletion (60%) = 900 x 0.6 = 540 g depleted\nCarbs/hr = 60 x 1.0 = 60 g/hr\nRepletion rate = 60 x 0.7 = 42 g/hr\nDelay penalty = 0.5 hr\nTime to full = (540 / 42) + 0.5 = 13.4 hours\nIn 6 hours: 42 x 5.5 = 231 g restored (43%)
Result: 13.4 hrs full recovery | In 6 hrs: 43% restored | Prioritize high-GI carbs
Frequently Asked Questions
What is the optimal carbohydrate intake rate for glycogen replenishment?
The optimal carbohydrate intake for maximizing glycogen replenishment is 1.0 to 1.2 grams per kilogram of body weight per hour during the first 4 to 6 hours after exercise. For a 70 kilogram athlete, this translates to 70 to 84 grams of carbohydrates per hour. Research has shown that intake rates above 1.2 grams per kilogram per hour do not further increase glycogen synthesis rates. High glycemic index carbohydrates such as white bread, rice, potatoes, and sports drinks are preferred because they produce rapid increases in blood glucose and insulin, both of which are critical for activating glycogen synthase, the enzyme responsible for glycogen storage. Spreading intake across smaller, frequent meals every 30 to 60 minutes is more effective than consuming large meals less frequently.
How does the type of exercise affect glycogen depletion and recovery?
Different types of exercise deplete glycogen at different rates and from different muscle fiber types, which affects recovery patterns. Continuous endurance exercise like running or cycling primarily depletes slow-twitch muscle fibers and can reduce glycogen by 60 to 85 percent after 2 to 3 hours of moderate intensity activity. High-intensity interval training depletes both slow-twitch and fast-twitch fibers more rapidly but may not reduce total glycogen as much due to shorter duration. Resistance training depletes glycogen primarily in the specific muscles worked, typically by 25 to 40 percent. Eccentric exercise like downhill running can damage muscle fibers and impair glycogen resynthesis for up to 72 hours. Understanding your specific exercise type helps set realistic expectations for recovery timelines.
What foods are best for rapid glycogen replenishment?
The best foods for rapid glycogen replenishment are high glycemic index carbohydrates that produce quick rises in blood glucose and insulin levels. Top choices include white rice, white bread, potatoes, pasta, rice cakes, pretzels, cereals, bananas, dates, and honey. Sports drinks and recovery shakes are excellent immediately after exercise because they are easy to consume and rapidly absorbed. Combining carbohydrates with a moderate amount of protein in a 3:1 or 4:1 ratio optimizes both glycogen synthesis and muscle repair. Avoid high-fat foods during the early recovery window as fat slows gastric emptying and can delay carbohydrate absorption. As recovery progresses beyond the first 4 to 6 hours, gradually transition to whole foods with more balanced macronutrient profiles for sustained glycogen replenishment.
How does sleep affect glycogen recovery after intense exercise?
Sleep plays an important role in glycogen recovery after intense exercise through several mechanisms. During sleep, growth hormone secretion increases significantly, which promotes anabolic processes including glycogen storage. The body also shifts from using carbohydrates as fuel to primarily oxidizing fats, which spares any remaining glycogen stores and allows continued glycogen synthesis from dietary carbohydrates consumed before bed. Getting 7 to 9 hours of quality sleep after intense training has been shown to improve glycogen recovery rates compared to sleep-deprived athletes. A carbohydrate-rich snack consumed 30 to 60 minutes before bedtime can provide substrate for overnight glycogen synthesis. Poor sleep quality or insufficient sleep duration can impair insulin sensitivity, reducing the efficiency of glycogen replenishment.
Can I train again before glycogen is fully replenished?
You can train again before glycogen is fully replenished, but the quality and intensity of your subsequent workout will be affected. Training with partially depleted glycogen stores reduces your capacity for high-intensity work and may increase perceived exertion at the same absolute intensity. However, some coaches deliberately prescribe low-glycogen training sessions as a strategy to enhance metabolic adaptations including improved fat oxidation and mitochondrial biogenesis. If your next session requires high intensity or is a competition, prioritize full glycogen restoration by allowing adequate recovery time and consuming optimal carbohydrate amounts. For twice-daily training, consume at least 1.0 to 1.2 grams of carbohydrates per kilogram per hour between sessions and include protein-rich foods to support recovery.
How do I know my glycogen stores are depleted after a workout?
While you cannot directly measure muscle glycogen without a muscle biopsy, several practical indicators suggest significant glycogen depletion. The most obvious sign is severe fatigue and inability to maintain exercise intensity, commonly known as bonking or hitting the wall. Other indicators include difficulty concentrating, mood changes, excessive hunger particularly for carbohydrate-rich foods, feeling cold during or after exercise, and delayed recovery of normal energy levels. The extent of depletion can be estimated based on exercise duration and intensity: moderate exercise for 90 minutes typically depletes 30 to 50 percent, while hard exercise for 2 to 3 hours can deplete 60 to 85 percent. Very long or intense sessions can result in near-complete glycogen depletion of 85 to 100 percent.