An athlete as asking me recently about liver and muscle glycogen stores and the impact on performance both pre and post workouts.
Muscle glycogen is used in workouts to perform actions and movements.
There is some discussion as to whether muscle glycogen can migrate in workouts (i.e. inactive muscle to active muscle), but nothing to substantiate it, so we assume very little migration at best. When muscle glycogen drops too low, muscles can’t relax between contractions anymore (i.e. no more fast movements, slower and slower, and slower…)
Liver glycogen is used to replace or maintain blood glucose levels (i.e. that drop overnight or during workouts to maintain blood glucose levels in the brain as working muscles import glucose as fuel). Blood glucose levels are essential to maintaining brain function, including execution of technical skills, using tactics, emotion management, remembering the workout, how many laps, etc.
In refueling after a workout, your snack should reflect the nature of the workout to some degree. Low intensity workouts can be more carbs (>80% or more complex carbohydrates- a mix of short through long chain carbs) and less protein, while higher intensity workouts can have more protein as you can burn up to 10% of your total calories from protein. Given that protein can be converted to carbs over a slightly longer time, higher intensity exercise recovery snacks can be up to 30% protein. Ideally protein should be from quickly and fully digestible protein sources (i.e. eggs, dairy, lean animal meats).
There is a two hour window post workout where glycogen can be synthesized very fast, enough to replenish all you lost plus a little extra. If you miss this window, it can be another 48 hours to reload or you can risk bonking in your workouts.
The idea is to “slowly fill the tank” as muscles can only take in so much glucose at a time. Excess glucose in the blood may trigger an insulin response where insulin is released, fat metabolism is shut down and fat storage increased. Not ideal for maintaining lean mass or replenishing glycogen.
Protein eaten earlier in the refueling can be used to rebuild blood amino acid levels, rebuild damaged tissues and over time converted to carbohydrates. Some theories suggest that eating higher protein post workout results in slower carb/glycogen release, minimal insulin response and maximal glycogen synthesis. No solid proof on that theory either. However, many high performance coaches and athletes swear by its results for promoting fat losses and optimal lean muscle mass retention.
So in summary-
- EAT proper post workout nutrition (0.5-1.0 g/kg carbohydrate (CHO) + 0.3-0.4 g/kg protein (PRO)) spread over the 2 hours post workout in 10-15 min blocks
- i.e. 0.125 g/kg CHO + 0.05 g/kg PRO every 15 min) either in liquid or solid form.
- High quality protein (i.e. whey protein) and more branch chain amino acids (BCAA) earlier in the refuelling window is better.
- CHO should be balance of short , medium and long chain.
- 2 bagels with peanut butter eaten in quarters every 15 min for two hours will do the trick after a long (2-3+ hours) or intense (1:00+ hours) workout
If you don’t refuel, intensity and possibly even duration of workouts has to be reduced. All speeds get pulled back to to 40-50% peak aerobic levels and skill levels drop increasing the risk of both injuries and accidents.