It’s known that repeated bouts of high intensity and prolonged aerobic exercise can lead to a depletion of both muscle and liver glycogen concentrations. This can impair aerobic exercise, reduce recovery from exercise and lead to increased levels of muscle breakdown. Therefore, it is important that you replenish muscle glycogen stores as quickly as possible – ideally you would replenish a large amount of glycogen within the first couple of hours after exercise.
Recommended carbohydrate intake after aerobic exercise
Current recommendations for replenishing glycogen stores are to consume approximately 1-1.2g of carbohydrate per kg of bodyweight immediately upon completion of exercise (Burke 2010; Goh et al., 2012;). This is normally achieved by consuming around 50-75g of quick releasing carbohydrate – normally a blend of glucose and maltodextrin – immediately upon completion of aerobic exercise, followed by a second high carbohydrate meal/drink a further 60-90 minutes later.
High GI carbs vs Low GI carbs after exercise
Whilst it is generally considered better to consume low GI foods prior to exercise the reverse is true after exercise. High GI carbs are more effective at rapidly replenishing muscle glycogen levels and are therefore desired over low GI sources post exercise. The main advantages with high GI carbohydrate source are that they are more readily digested, enter the blood stream more quickly, and are therefore available more quickly for glycogen re-synthesis rates. Following a prolonged aerobic activity (e.g. a 2-hour run or 3-hour cycle) you will need to continue to consume high levels of carbohydrate throughout the day – normally you would aim to consume additional carbohydrate every 2-3hours. Endurance athletes may need to consume around 500-600g/day of carbohydrate (~twice the normal recommended carbohydrate intake) in order to maintain muscle glycogen levels.
Carbohydrates can help to reduce levels of muscle breakdown
In addition to replenishing muscle and liver glycogen levels, a large post exercise carbohydrate consumption can help to reduce the breakdown of muscle protein and may increase levels of protein synthesis (muscle building). This is particularly important when you consider that following endurance training, a large amount of the working muscles will have damaged muscle fibres that will need to be rebuilt in order for complete recovery to occur. If additional carbohydrate is not consumed then further proteins may be broken down for use as energy during the rebuilding process. Post-exercise carbohydrate consumption may also help to protect against elevation of cortisol levels which are known to increase levels of muscle breakdown.
Consuming large amounts of high GI carbohydrates post-exercise increases insulin levels which can help to drive carbohydrates into muscles and may enhance the building of new muscle tissue. This is because insulin is an anabolic hormone – that is it encourages the building of new muscle tissue – and therefore increased post exercise insulin levels can have a positive impact on muscle protein synthesis.
Combining carbs with protein can further enhance recovery from exercise
To further enhance recovery endurance athletes should consider consuming whey protein or BCAAs (Branched Chain Amino Acids) along with initial recovery drink. This is supported by research which has demonstrated that the consumption of carbohydrate along with either protein (Goh et al., 2012; Ferguson-Stegall et al., 2011; Karp et al., 2006; Koopman et al., 2004;), or, BCAAs (Negro et al., 2008; Schena et al., 1992;) can be beneficial for post exercise recovery, rates of muscle protein synthesis, increase rates of glycogen replenishment and enhance subsequent exercise performance.
Carbohydrates after exercise summary:
- High intensity and prolonged aerobic exercise can lead to depleted muscle glycogen stores.
- If muscle glycogen stores are not replaced there will be increased rates of muscle breakdown and reduced levels of recovery following exercise.
- Current recommendations for replenishing muscle glycogen stores are to consume 1-1.2g of carbohydrate per kg of bodyweight.
- High GI carbs appear to be more beneficial than low GI carbs
- The most convenient way to do this is to consume approximately 50-75g of quick releasing carbs in a drink immediately upon completion of exercise. Following prolonged exercise (>1 hour) a second dose may be consumed – normally around 90 minutes later.
- A high carbohydrate intake can help to reduce rates of muscle breakdown and enhance post exercise recovery.
- Comining protein (particularly protein rich in BCAAs) can further enhance recovery and improve the rates of muscle glycogen replenishment.