Sarah Gibson, UH Dietetic Intern and Edited by Meredith Sorensen, MS, RD, CSSD, LD Memorial Hermann Sports Medicine Institute
What is the Function of Carbohydrates?
Carbohydrates are the main energy source obtained through food and are broken down in the body into glucose, also known as blood sugar. Glucose is used in the body immediately or stored in the liver and muscles as glycogen for later use. Carbohydrates are important in the diet because they provide fuel both during and after resistance exercise (RE). Resistance exercise (RE) is training that focuses on exercises targeting specific muscle groups for both upper and lower body. Having insufficient stores during RE results in decreased performance because muscle fibers rely on glycogen for maximum force production6. Research has shown that in RE, training longer than 45 minutes reduces glycogen stores, specifically type II muscle fibers by 24-40%, which are responsible for the force production necessary during RE6. If there are not adequate glycogen stores, output during performance is decreased resulting in decreased performance.
Carbohydrates and Recovery
What is recovery?
Recovery is important for both recreational and competitive athletes and involves utilizing techniques after training in order to reduce fatigue and muscle soreness in an attempt to return to yesterday.
How do carbohydrates play a role in recovery?
In the first five to six hours after RE, there are two phases of rebuilding glycogen that occur1. The first phase is quick when carbohydrate intake is adequate and will last 30-60 minutes after exercise. If there are not enough carbohydrates consumed, this rate of this phase will decrease. The second phase is slower than the first phase. However, just like in the first phase, an adequate intake of carbohydrates is required to rebuild glycogen stores. This phase can extend longer than 48 hours but will depend on the amount of carbohydrate intake and the amount of glycogen restored to muscles for this to continue1.
Carbohydrate supplementation after RE has been shown to increase muscle growth in type IIA and IIX fibers, decrease fat mass, increase lean body mass, and increase strength and muscle fiber area4. Restoring muscle glycogen stores results in an increase in strength demonstrated in specific lifts (barbell squat, bench press, and deadlift)4 and greater gains in body mass and lean body mass. This demonstrates that carbohydrates function in sparing muscle glycogen stores by increasing work capacity during RE which provides an enhanced development of strength and muscle growth4. In one study, individuals who incorporated carbohydrates after RE increased their 1RM in barbell lifts such as the barbell back squat and bench press, and press4. Another study comparing carbohydrate and creatine to carbohydrate and protein found similar increases in muscle fibers and strength from 14%-40% in exercises that targeted specific muscle groups such as legs, chest, back, shoulder and arms when 75 g of carbohydrates were consumed within 30 minutes after exercise8. Another study showed that carbohydrate consumption after RE was sufficient in improving the rate of muscle glycogen rebuilding but was also important during a short-term recovery period following RE3. After the first four hours of RE, the rate of muscle glycogen concentrations were measured and were shown to increase by 66.8% when carbohydrates were consumed after RE compared to carbohydrate and protein alone at 56.4%3. Overall, carbohydrate intake after RE rebuilds glycogen stores while reducing muscle protein breakdown, leading to optimal recovery and improved performance for future training sessions.
Timing of Carbohydrates
Research has shown that timing of carbohydrates affects muscle growth and strength development. As stated earlier, the first phase of glycogen restoring lasts 30-60 minutes after RE. The second phase of rebuilding lasts up to 48 hours but requires frequent intake of carbohydrates in order to fully restore glycogen stores. During a limited window for recovery (1-5 hours), it is important to consume carbohydrates as soon as possible after RE, at least within 1-2 hours. For example, an athlete who has just completed a weightlifting session and has their next training session in 3 hours would need to consume carbohydrates at the latest, 2 hours after their training session. The goal is to eat as soon as possible to replenish stores that were lost to maximize recovery. It is important to note that consuming protein after RE does not affect the rate of muscle glycogen rebuilding. However, when there is a smaller amount of carbohydrate intake, additional protein combined with carbohydrate does provide recovery benefits including muscle repair3.
For a long-term recovery window that is greater than 8 hours and up to 48 hours, it is important to consume carbohydrate rich meals every 2-3 hours to refuel lost stores. An example is an individual who goes to the gym to train during their lunch break. After their session, they rush to shower and get back to work and go straight into a meeting that lasts one hour. By the time they are able to get their post-recovery meal in, two hours have passed. In this scenario, it is not as important to get in fuel in right away since the recovery period between training sessions is roughly 24 hours. However, it is still important that their recovery meal does contain a good amount of carbohydrates to rebuild lost stores, promote recovery, and provide energy for the rest of their day and their next training session.
Types of Carbohydrates
During a limited recovery window, it is important to focus on specific sources of carbohydrates for optimal recovery. Carbohydrates that are simple (high-glycemic) will increase muscle glycogen stores more effectively in short-term recovery scenarios because they are digested quickly. Examples of simple carbohydrates include applesauce, whole fruit, or pretzels. An example scenario would be an athlete who has tournaments within 2-hours of each other. During the 2-hour break, it would be best for this athlete to consume a simple carbohydrate such as an applesauce packet or a Gatorade if they have a low appetite. Sports drinks are a great option when an athlete is unable to stomach food.
During a long-term recovery window, the focus should instead shift to complex carbohydrates (low-glycemic) that require time to digest, providing longer-lasting energy. In the example of the individual going to the gym during their lunch, an example of a carbohydrate source for their meal after RE might be brown rice, whole grain bread, or potatoes.
Another example is a recreational athlete who has two training sessions at the gym. The first session runs from 10am – 11:30am and the second session begins at 2:30pm. After their 10am training session, for optimal recovery, it would be best to have a simple carbohydrate source such as a banana paired with a source of lean protein as soon as possible to restore glycogen stores. After their 2:30pm training session, the recovery meal can contain more complex carbohydrates such as brown rice or potatoes paired with a lean protein source since their next session will not be until the following day.
An example of carbohydrate sources after RE based on short and long-term windows for recovery is provided for a 60 kg (132lb) female recreational athlete ranging from 1-4h+ hours between next training session. The carbohydrate recommendation is 1 g/kg of body weight. To convert from lbs. to kg, divide the weight in lbs. by 2.2 kg. A 1-hour recovery period focuses on simple, fast acting carbohydrates such as 12 oz Gatorade and/or applesauce packets which will provide fuel quickly in the short amount of time. Liquid carbohydrate sources are often times easier to stomach during a short recovery period. A 2-hour recovery period may incorporate lean protein sources such as a Gatorade recovery shake that contains carbohydrates paired with a fast-acting carbohydrate such as an applesauce packet. A 3-hour recovery window may also incorporate lean protein as well as a mixture of complex and simple carbohydrate sources such as sandwich bread (white or whole grain) and a banana. A 4-hour+ recovery window also incorporates a lean protein, complex carbohydrates such as pasta, some greens and a side of fruit for color.
Overall, carbohydrates are important in enhancing recovery. Consuming simple carbohydrates during a limited window for recovery will increase muscle glycogen stores more effectively because they are digested quickly. When an extended window for recovery exists, incorporating a mixture of both simple and complex carbohydrates every 3-4 hours at meals is best to maintain glycogen stores. This provides energy throughout the day, reduces fatigue, and reduces muscle soreness when going into the next training session.
Have questions? Please feel free to talk to an Athlete Training and Health Performance Coach or Meredith Sorensen, Sports Dietitian, MS, RD, LD with the Memorial Hermann Rockets Sports Medicine Institute. Meredith can be reached at Meredith.Sorensen@memorialhermann.org or can be found on Instagram at @meredithdarcienutrition.
Alghannam, A. F., Gonzalez, J. T., & Betts, J. A. (2018). Restoration of Muscle Glycogen and Functional Capacity: Role of Post-Exercise Carbohydrate and Protein Co-Ingestion. Nutrients, 10(2), 253. https://doi.org/10.3390/nu10020253
Arent, S. M., Cintineo, H. P., McFadden, B. A., Chandler, A. J., & Arent, M. A. (2020). Nutrient Timing: A Garage Door of Opportunity? Nutrients, 12(7), 1948. https://doi.org/10.3390/nu12071948
Craven, J., Desbrow, B., Sabapathy, S., Bellinger, P., McCartney, D., & Irwin, C. (2021). The Effect of Consuming Carbohydrate With and Without Protein on the Rate of Muscle Glycogen Re-synthesis During Short-Term Post-exercise Recovery: a Systematic Review and Meta-analysis. Sports Medicine - Open, 7(1). https://doi.org/10.1186/s40798-020-00297-0
Cribb, P. J., & Hayes, A. (2006). Effects of Supplement Timing and Resistance Exercise on Skeletal Muscle Hypertrophy. Medicine and Science in Sports and Exercise, 38(11), 1918–1925. https://doi.org/10.1249/01.mss.0000233790.08788.3e
Gonzalez, J. T., Fuchs, C. J., Betts, J. A., & Van Loon, L. J. C. (2017). Glucose Plus Fructose Ingestion for Post-Exercise Recovery—Greater than the Sum of Its Parts? Nutrients, 9(4), 344. https://doi.org/10.3390/nu9040344
King, A. J., Helms, E. R., Zinn, C., & Jukic, I. (2022). The Ergogenic Effects of Acute Carbohydrate Feeding on Resistance Exercise Performance: A Systematic Review and Meta-analysis. Sports Medicine, 52(11), 2691–2712. https://doi.org/10.1007/s40279-022-01716-w
Roy, B. D., & Tarnopolsky, M. A. (1998). Influence of differing macronutrient intakes on muscle glycogen resynthesis after resistance exercise. Journal of Applied Physiology, 84(3), 890–896. https://doi.org/10.1152/jappl.19184.108.40.2060
Tarnopolsky, M. A., Parise, G., Yardley, N. J., Ballantyne, C. M., Olatinji, S., & Phillips, S. F. (2001). Creatine-dextrose and protein-dextrose induce similar strength gains during training. Medicine and Science in Sports and Exercise, 33(12), 2044–2052. https://doi.org/10.1097/00005768-200112000-00011