In a recent blog, I discussed the amount of total daily carbohydrate intake for athletes.  Another important factor regarding carbohydrate intake is the timing of ingestion of carbohydrates. When we think about the timing of carbohydrates, we can think about three distinct periods: 1) pre-exercise, 2) during exercise, and 3) post-exercise.  

Pre-Exercise Carbohydrate Intake
Consuming carbohydrates prior to exercise is important in restoring liver and muscle glycogen levels from an overnight fast and/or from a previous exercise session. Restoring carbohydrate storage (i.e., glycogen) levels during the pre-exercise carbohydrate ingestion period also aids in preventing hunger and maintaining blood glucose levels during exercise. 

The pre-exercise meal should contain between 1 and 4 grams of carbohydrate per kilogram of body weight and be consumed 1 to 4 hours before exercise [Burke et al., 2011; Sherman et al., 1989; Sherman et al., 1991]. The closer to the exercise bout, the athlete should reduce the amount of carbohydrate [See Table 1 Below; Adapted from Coleman, 2017].

During Exercise Carbohydrate Intake 
The next period to consider for carbohydrate intake is during the actual exercise bout. For exercise lasting less than 30 minutes, there really is no need to ingest carbohydrates during exercise.  However, for events or excercise lasting longer than 30 minutes, the amount and type of carbohydrates ingested during exercise is dependent on the duration and intensity of the exercise (Table 2, adapted from Coleman, 2017]. 

For continuous high-intensity exercise lasting between 30 and 75 minutes, consuming small amounts of carbohydrates is recommended [Jeukendrup, 2014]. This can take the form of single or multiple transportable carbohydrates or even a carbohydrate rinse [Coleman, 2017]. For endurance exercise or intermittent high-intensity exercise lasting between 60 and 120 minutes, athletes should consume 30 grams of carbohydrate per hour [Coleman, 2017]. Athletes participating in prolonged endurance exercise lasting between 120 and 180 minutes should consume 60 grams per hour of carbohydrates [Coleman, 2017]. Finally, for prolonged endurance exercise lasting more than 180 minutes, athletes should consume about 90 grams per hour of carbohydrates. It is important to remember that some athletes may have trouble with gut tolerance to high levels of carbohydrate intake so adjust amounts to accommodate these athletes.

Post-Exercise Carbohydrate Intake
Following exercise, the restoration of muscle and liver glycogen stores is essential.  Therefore, it is important for athletes to start carbohydrate ingestion as soon as possible after exercise. Athletes should consume 1 to 1.2 grams of carbohydrate/kilogram of body weight/hour for the first 4 hours after exercise [Coleman, 2017]. 

For some athletes, this recommended amount of carbohydrate may cause gut indigestion issues.  Adding a small amount of protein [0.3 grams of protein/kilogram body weight/hour with 0.8 grams of carbohydrate/kilogram body weight/hour] can help with gut intolerances.  Consuming small amounts of protein after exercise also helps stimulate muscle protein synthesis and inhibit protein breakdown. Therefore, a carbohydrate/protein mix is recommended for post-exercise recovery.

Take Home Message
Carbohydrate intake for pre-exercise, during and post-exercise plays a critical part in an athlete’s performance.  The timing and amount of carbohydrates are important when developing a fueling plan. Furthermore, each athlete should follow a tailored plan based on body weight, duration, and intensity of the exercise bout as well as gut tolerance. 

References

Burke LM, Hawley JA, Wong S, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci. 2011; 29(suppl 1):17S-27S.

Coleman EJ. Carbohydrate and exercise. In Sports Nutrition: A Handbook for Professionals. 6th edition. Karpinski C (Ed). Academy of Nutrition and Dietetics 2017.

Jeukendrup AE. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med. 2014;44(suppl 1):25S-33S.

Sherman WM, Brodowicz G, Wright DA, Allen WS, Simonsen J, Dernbach A. Effect of 4 hour pre-exercise carbohydrate feedings on cycling performance. Med Sci Sports Exerc. 1989; 21(5):598-604.

Sherman WM, Peden MC, Wright DA. Carbohydrate feedings 1 hour before exercise improves cycling performance. Am J Clin Nutr. 191; 54(5):866-870.

About the Author

Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.