How fast do your energy stores recover from prolonged exercise?

Carbohydrates are the main fuel source during moderate to high-intensity prolonged exercise (Van Loon et al, 2001). A limited amount of carbohydrates is stored in the liver and muscle as glycogen.

Muscle glycogen depletion has been associated with fatigue. Therefore, muscle glycogen stores should be maximized to optimize performance during prolonged exercise.

However, a long and intensive exercise session can deplete muscle glycogen stores. Carbohydrate ingestion will help rebuild (resynthesize) muscle glycogen. But how long does it take before depleted muscle glycogen stores are restored?

The current study investigated the resynthesis of muscle glycogen after prolonged cycling until exhaustion (~3 h). Subjects were instructed to consume a high-carbohydrate diet (>80% of total energy coming from carbs) after the exercise session.

Muscle glycogen stores were almost fully depleted immediately after the intense exercise session. However, the carbohydrate stores in the muscle were completely recovered 1 day after the exercise.

Therefore, it might take a day before you can have optimal performance again with prolonged exercise, such as cycling. It should be noted that this can differ between sports. For example, muscle glycogen recovery is slower after soccer exercise (Krustrup et al, 2011). This is likely because muscle damage may impair muscle glycogen synthesis (Costill et al, 1990).

In conclusion, it can take up to 24 hours to fully restore muscle glycogen stores after exhaustive cycling exercise.

Study:

Casey et al. Glycogen resynthesis in human muscle fibre types following exercise-induced glycogen depletion. J Phyiol, 1995

Go to the next infographic in the carbohydrate series:

Muscle glycogen is not limiting during resistance exercise?