One click onto social media and you will find hundreds of posts focusing on protein and how we need to get enough. However did you know that protein is not the most important energy source for your working muscles?
What is glycogen?
When we eat foods that contain carbohydrates, such as fruit, grains, beans and legumes, dairy, sports foods like sport drinks and gels, sweets and snack foods, they are broken down to the single units glucose, fructose and/or galactose which are absorbed into the bloodstream (Canadian Sugar Institute, 2024). When your body does not need them right away, they are stored for future use as glycogen. Glycogen is the storage form of carbohydrates found in most cells with the majority stored in skeletal muscle and liver cells. It can be converted back to glucose when the body needs energy and when blood glucose levels are low. Glucose is the primary fuel source for the brain and red blood cells as well as the preferred energy source for working muscles during physical activity.
Carbohydrate needs to support glycogen
The amount of glycogen stored in the body depends on:
- Your daily intake of carbohydrates
- Your level of training
- Whether you carbohydrate load prior to training or competition.
The US Institute of Medicine recommends we eat at least 130 grams of carbohydrates each day with additional carbohydrates needed to match what is burned during physical activity (Murray and Rosenbloom, 2018). An example of what this minimum amount looks like in a day:
- 2 slices of toast with a piece of fruit with breakfast
- Including a piece of fruit at a snack
- Including ½ cup of a cooked grain or 1 medium baked potato or sweet potato with both lunch and dinner
The additional amount we need to eat will depend on the duration and intensity of training, with more intense training and endurance training leading to larger declines in muscle glycogen. For example, sprinting will quickly lower glycogen stores in the muscle. Additionally, glycogen is greatly reduced when athletes train for hours at a time, such as marathon runners and cyclists. During strength training, glycogen levels can be reduced by up to 40% with larger reductions seen in sessions with higher repetitions and moderate loads (Knuiman et al., 2015)
For strength-based athletes, carbohydrate needs range from 4-7 grams per kilogram of body weight daily and for endurance based athletes, needs can be up to 10 grams per kilogram of body weight daily (Potgeiter, 2013). For someone who strength trains and is about 68kg (150lbs), they would be aiming for at least 270g daily.
Many athletes often do not consume enough carbohydrates to meet recommendations for their health and training needs. This can be due to lack of time due to busy training schedules and work, diet rules preventing them from eating enough, or a lack of knowledge around their specific needs. To support the body for training and competition, adequate glycogen stores are required.
Role of glycogen for performance and recovery
Consuming enough carbohydrates daily can optimize glycogen stores, improve exercise performance, support recovery, and maintain exercise capacity (Murray and Rosenbloom, 2018). Research has shown that energy from carbohydrates is required to sustain exercise intensities and support the energetic demands of muscle contraction (Knuiman et al. 2015), therefore when we do not have enough, training and competition performance can be impacted. When glycogen becomes depleted, intensity level drops and fatigue occurs. For runners and cyclists, you may have heard the expression ‘hitting the wall’. This is commonly used in the athletic space to describe how exercising with a lack of glycogen feels.
Restoring muscle and liver glycogen after exercise can support recovery and reduce the risk of compounded fatigue during the week. This is especially important when an athlete is exercising multiple times per day. It appears that eating soon after exercise can increase the rate of muscle glycogen refilling as compared to delaying the carbohydrate-containing meal or snack by 2-3 hours (Alghannam et al., 2018). Pairing carbohydrates with a source of protein after exercise may also speed up the rate of refilling of muscle glycogen stores.
How do we optimize glycogen stores?
- Make sure you are eating enough carbohydrates on a daily basis. Aim for carbohydrate rich foods with each meal. Aiming for 1/4 to 1/3 of the meal being a grain or starch such as rice, potatoes, or naan.
- Enjoy a carbohydrate (and protein) containing snack as soon as you can after exercise. An example might look like a fruit smoothie with greek yogurt.
- Work with a sport dietitian to build and enjoy meals and snacks that support your specific carbohydrate needs!
Sara Friedrich is a registered dietitian with expertise in sport nutrition, REDs and food and body relationship support. She is taking new clients and would love to support you with your performance and recovery goals. Book a discovery call or appointment to connect and work with Sara!
References:
Canadian Sugar Institute (2024). Carbohydrate digestion and absorption. https://sugar.ca/sugars-health/carbohydrate-digestion-and-absorption#:~:text=Digestion%20of%20Carbohydrates,-Before%20the%20body&text=During%20digestion%2C%20starches%20and%20sugars,as%20energy%20throughout%20the%20body.
Potgieter, S. (2013). Sport nutrition: A review of the latest guidelines for exercise and sport nutrition from the American College of Sport Nutrition, the International Olympic Committee and the International Society for Sports Nutrition. South African Journal of Clinical Nutrition, 26(1), 6–16. https://doi.org/10.1080/16070658.2013.11734434
Murray, B. and Rosenbloom, C. (2018). Fundamentals of glycogen metabolism for coaches and athletes. Nutrition Reviews. 76(4), 243-259. doi:10.1093/nutrit/nuy001
Alghannam, A.F., Gonzalez, J.T., and Betts, J.A, (2018). Restoration of Muscle Glycogen and Functional Capacity: Role of Post-Exercise Carbohydrate and Protein Co-ingestion. Nutrients. 10(2), 253. doi: 10.3390/nu10020253
Knuiman, P., Hopman, M.T.E., and Mensink, M. (2015). Glycogen availability and skeletal muscle adaptations with endurance and resistance exercise. Nutrition & Metabolism, 12(59). https://doi.org/10.1186/s12986-015-0055-9