Maximizing Post-Exercise Recovery with Carbohydrate plus Protein:
How and Why It Works
Lisa Ferguson-Stegall, PhD
The University of Texas at Austin Exercise Physiology & Metabolism Laboratory
The critical role of proper post-exercise nutrition has been well established through
decades of scientific research and practical application. While the importance of
carbohydrate intake has been well documented, recent investigations have
demonstrated the effectiveness of carbohydrate plus protein supplementation in
improving exercise performance in an acute bout, as well as in a second bout the same
day. In addition, carbohydrate+protein supplementation post-exercise has been shown
to be effective in restoring muscle glycogen, repairing muscle damage, attenuating
protein degradation and initiating protein synthesis – all positive outcomes that lead to
improved rate of recovery and adaptation to exercise training. In this article, we
describe the mechanisms by which carbohydrate+protein supplementation can improve
recovery and increase training adaptations more effectively than when ingesting either
nothing at all or carbohydrate only following an intense endurance exercise session.
THE POST-EXERCISE STATE
The body is in a catabolic state after an intense exercise session. Stress hormones are
high, muscle tissues is damaged, and fuel stores such as muscle glycogen are low or
possibly depleted. Making a shift to an anabolic, or rebuilding, state must happen
quickly in order to recover from the bout and adapt to the training stimulus. Endurance
athletes must often compete in multiple events per day, such as in cycling stage races,
or train twice per day, which means that there is little time to recover in between each
bout. Therefore, to facilitate this shift quickly and adequately, proper post-exercise
nutrition must be ingested, and the timing of intake must also be performed properly.
We have known for many years that carbohydrate intake can maintain blood glucose
and extend time to exhaustion during endurance exercise (4, 5), attenuate cytokine &
immune cell perturbations (20), increase glucose & insulin levels, and restore glycogen
levels (14, 29). In recent years, however, carbohydrate+protein has been shown to
increase time to exhaustion in endurance exercise beyond that of carbohydrate alone,
increase insulin and glycogen storage, and increase the rate of recovery such that
subsequent performance later in the same day is improved. Also, carbohydrate+protein
can increase the activation of pathways responsible for increased protein synthesis (11,
13, 24, 25). This is important for repairing damaged tissue and adapting to the training
stimulus through the synthesis of new proteins.
THE IMPORTANCE OF TIMING
The 30-60 minutes after an intense exercise session is often called the “recovery
window,” and for a good reason. Immediately post-exercise, the muscles are more
sensitive to nutritional stimuli, so this is the ideal time to take in nutrients in order to
restore muscle glycogen and activate protein synthesis. Nutrient intake during this time
can also help prevent additional protein breakdown that occurs in the absence of
nutrient intake post-exercise (2), and can attenuate the cortisol response, which if left
unchecked leads to further catabolism (19). The co-ingestion of carbohydrate and
protein is more effective than either of the macronutrients alone because they activate
different but cooperative signaling pathways that control glucose uptake, glycogen
synthesis, and protein synthesis, as well as protein degradation. This is illustrated in the
figure below.
Just as skeletal muscle is most sensitive to insulin and nutritional substrate for glycogen
resynthesis immediately post-exercise, the stimulation of protein synthesis, which will be
discussed more below, is most responsive immediately after exercise as well. One
group of researchers assessed the role of supplement timing on protein synthesis by
providing a carbohydrate+protein supplement either immediately after, or 3 hours after a
moderate-intensity cycling exercise bout (18). They found that when the supplement
was ingested immediately post-exercise, whole body protein synthesis was increased
by 300%, compared to only 12% when the supplement was delayed by 3 hours (18).
This illustrates the importance of ingesting carbohydrate+protein immediately postexercise, rather than delaying supplementation.
Two key intracellular signaling pathways are activated when a supplement containing both
carbohydrate and protein is ingested post-exercise. Blood glucose rises due to the carbohydrate,
which stimulates an increase in blood insulin. When insulin binds to its receptor of the membrane of the
muscle cells, it activates a signaling cascade, which reaches downstream targets AS160 and GSK-3.
AS160 normally inhibits the process through which glucose enters the cell, but when the signaling protein
Akt phosphorylates it, the inhibition is relieved and cellular glucose uptake can occur. In a similar fashion,
the enzyme glycogen synthase, which controls glycogen synthesis, is normally inhibited by GSK-3. When
GSK-3 is phosphorylated by Akt, the inhibition is removed and the process of glycogen synthesis can
proceed. Phosphorylation of GSK-3 also affects mRNA translation initiation and protein synthesis by
relieving the inhibition of eIF2B, which is a critical initiation factor. The protein component of the
supplement increases the level of blood amino acids, which leads to activation of the mTOR pathway.
This pathway ultimately controls protein synthesis, which is at the heart of recovery and adaptation to the
exercise stimulus. Arrows between the pathways show that the pathways interact, which amplifies the
signals further.
OPTIMIZING GLYCOGEN RESYNTHESIS
A long, intense endurance exercise session can leave your body’s carbohydrate stores
(e.g., muscle and liver glycogen) extremely low or even depleted, and without adequate
carbohydrate intake, very little glycogen resynthesis and storage can occur (12, 13, 30).
Ingesting carbohydrate immediately after exercise is beneficial because it provides an
immediate source of fuel for muscle to use to replace the glycogen that has been used.
We know that ingesting a carbohydrate supplement immediately post-exercise doubles
the rate of glycogen synthesis compared to ingesting the very same supplement 2 hours
following exercise (12). Although some studies have shown that more frequent
supplementation such as every 15 to 30 minutes results in rates of synthesis 25-30%
higher than when supplementing every two hours (8, 28), this is a high amount of
carbohydrate to ingest, and simply may not be practical for many individuals. A more
realistic and practical strategy is simply to ingest a supplement immediately postexercise, and again about 2 hours later. Generally, the amount of carbohydrate and
protein that is most effective after prolonged endurance exercise ranges between 1.21.5 grams of carbohydrate per kg body weight and 0.4-0.6 grams protein per kg when
provided immediately post-exercise and 2 hours later. This can be achieved in the form
of commercial supplements or as a meal.
TURNING ON PROTEIN SYNTHESIS FOR REPAIR AND ADAPTATION
Increased muscle protein synthesis is at the heart of adaptation to exercise training. The
increased proteins include contractile fibers, oxidative enzymes, mitochondria,
membrane receptors, hemoglobin, substrate transporters, and many other important
cellular and molecular factors that have key functions related to exercise performance.
Many investigations have shown that the addition of protein, especially the essential
amino acids, to a post-exercise carbohydrate supplement can optimize protein
synthesis, create a positive protein balance, repair muscle damage, and stimulate
positive training adaptations (1, 7, 9, 10, 16, 17, 21, 26). Carbohydrate+protein can
reduce muscle protein breakdown, primarily due to increased insulin levels. Insulin,
known for its key role in clearing glucose from the blood and stimulating its uptake into
cells, is one of the body’s most anabolic hormones. Insulin’s most powerful role postexercise is in reducing protein degradation (2, 3). Therefore, when a supplement
containing carbohydrate causes an increase in insulin and the protein component
provides the amino acids as building blocks for tissue repair and protein synthesis, the
result is that the net protein balance shifts because the rate of synthesis now exceeds
the rate of breakdown (26).
Several investigations have demonstrated reduced muscle damage following intense
endurance exercise in response to carbohydrate-protein supplementation compared to
carbohydrate alone or a placebo treatment (6, 22-25). In one such study, trained
cyclists performed an intense cycling ride to exhaustion while receiving carbohydrate,
carbohydrate+protein or a placebo during the ride (27). After a 24-hour recovery period,
the cyclists performed leg extensions to fatigue. The cyclists were able to perform a
greater number of leg extension repetitions after having the carbohydrate+protein
treatment compared to the carbohydrate or placebo treatments. In addition, the time to
exhaustion during the initial cycling session was longer during the carbohydrate+protein
treatment, and a significant decrease in markers of muscle damage was detected with
the carbohydrate+protein supplement after the cycling bout (27). While the mechanisms
by which carbohydrate+protein may reduce muscle damage are yet to be completely
elucidated, it is likely that insulin’s role in reducing muscle protein degradation is a key
factor.
APPLYING THIS TO YOUR TRAINING AND NUTRITIONAL PLAN
We all know that recovery from intense endurance exercise is a multifaceted process,
and is very important. Ingestion of carbohydrate+protein supplementation after exercise
can optimize many aspects of the recovery process, as well as facilitate adaptations to
training. Providing carbohydrate+protein supplementation immediately and 2 hours post
exercise can increase the rate and amount of muscle glycogen restoration, reduce
muscle damage, and increase the rate of muscle protein synthesis to a greater degree
than when ingesting carbohydrate or protein alone. This means that you can both
recover and adapt better to the training stimulus.
Therefore, in order to apply this nutritional strategy to your post-endurance exercise
routine, ingest a beverage or a meal containing 1.2-1.5 grams of carbohydrate plus 0.40.6 grams protein per kg of body weight immediately after exercise and again about 2
hours later. (Whenever possible, the protein source should contain whey, as this has
been found to be most effective in stimulating protein synthesis (51).) For a 70 kg
person, these recommendations translate to about 84-105 g carbohydrate plus 28-42 g
protein, totaling 450-600 kcal per supplement after workouts are intense and prolonged.
For workouts that are less intense or of short duration, a good rule of thumb is to
replace about 50% of the calories expended in your workout with a
carbohydrate+protein supplement. Intake of the right amounts of carbohydrate and
protein and at the optimal times after exercise can help assure that you get the most out
of your workout and your training program.
REFERENCES
1. Biolo G, Tipton KD, Klein S, and Wolfe RR. An abundant supply of amino acids
enhances the metabolic effect of exercise on muscle protein. Am J Physiol
Endocrinol Metab 273: E122-129, 1997.
2. Biolo G, Williams BD, Fleming RY, and Wolfe RR. Insulin action on muscle protein
kinetics and amino acid transport during recovery after resistance exercise. Diabetes
48: 949-957, 1999.
3. Borsheim E, Cree MG, Tipton KD, Elliott TA, Aarsland A, and Wolfe RR. Effect of
carbohydrate intake on net muscle protein synthesis during recovery from resistance
exercise. J Appl Physiol 96: 674-678, 2004.
4. Coggan AR, and Coyle EF. Effect of carbohydrate feedings during high-intensity
exercise. J Appl Physiol 65: 1703-1709, 1988.
5. Coggan AR, and Coyle EF. Reversal of fatigue during prolonged exercise by
carbohydrate infusion or ingestion. J Appl Physiol 63: 2388-2395, 1987.
6. Combest T, Saunders M, Kane M, and Todd K. Attenuated CPK Following
Carbohydrate/protein Intervention Improves Subsequent Performance. Med Sci
Sports Exc 37: S42, 2005.
7. Cribb PJ, and Hayes A. Effects of supplement timing and resistance exercise on
skeletal muscle hypertrophy. Med Sci Sports Exerc 38: 1918-1925, 2006.
8. Doyle JA, Sherman WM, and Strauss RL. Effects of eccentric and concentric
exercise on muscle glycogen replenishment. J Appl Physiol 74: 1848-1855, 1993.
9. Flakoll PJ, Judy T, Flinn K, Carr C, and Flinn S. Postexercise protein
supplementation improves health and muscle soreness during basic military training
in marine recruits. J Appl Physiol 96: 951-956, 2004.
10. Gautsch TA, Anthony JC, Kimball SR, Paul GL, Layman DK, and Jefferson LS.
Availability of eIF4E regulates skeletal muscle protein synthesis during recovery
from exercise. Am J Physiol Cell Physiol 274: C406-414, 1998.
11. Ivy JL, Ding Z, Hwang H, Cialdella-Kam LC, and Morrison PJ. Post exercise
carbohydrate-protein supplementation: phosphorylation of muscle proteins involved
in glycogen synthesis and protein translation. Amino Acids 35: 89-97, 2008.
12. Ivy JL, Katz AL, Cutler CL, Sherman WM, and Coyle EF. Muscle glycogen synthesis
after exercise: effect of time of carbohydrate ingestion. J Appl Physiol 64: 14801485, 1988.
13. Ivy JL, Lee MC, Brozinick JT, Jr., and Reed MJ. Muscle glycogen storage after
different amounts of carbohydrate ingestion. J Appl Physiol 65: 2018-2023, 1988.
14. Ivy JL, Miller W, Dover V, Goodyear LG, Sherman WM, Farrell S, and Williams H.
Endurance improved by ingestion of a glucose polymer supplement. Med Sci Sports
Exerc 15: 466-471, 1983.
15. Ivy JL, Res PT, Sprague RC, and Widzer MO. Effect of a carbohydrate-protein
supplement on endurance performance during exercise of varying intensity. Int J
Sport Nutr Exerc Metab 13: 382-395, 2003.
16. Koopman R, Wagenmakers AJM, Manders RJF, Zorenc AHG, Senden JMG,
Gorselink M, Keizer HA, and van Loon LJC. Combined ingestion of protein and free
leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in
male subjects. Am J Physiol Endocrinol Metab 288: E645-653, 2005.
17. Levenhagen DK, Carr C, Carlson MG, Maron DJ, Borel MJ, and Flakoll PJ.
Postexercise protein intake enhances whole-body and leg protein accretion in
humans. Med Sci Sports Exerc 34: 828-837, 2002.
18. Levenhagen DK, Gresham JD, Carlson MG, Maron DJ, Borel MJ, and Flakoll PJ.
Postexercise nutrient intake timing in humans is critical to recovery of leg glucose
and protein homeostasis. Am J Physiol Endocrinol Metab 280: E982-993, 2001.
19. Nieman DC. Immune response to heavy exertion. J Appl Physiol 82: 1385-1394,
1997.
20. Nieman DC. Influence of carbohydrate on the immune response to intensive,
prolonged exercise. Exerc Immunol Rev 4: 64-76, 1998.
21. Rasmussen BB, Tipton KD, Miller SL, Wolf SE, and Wolfe RR. An oral essential
amino acid-carbohydrate supplement enhances muscle protein anabolism after
resistance exercise. J Appl Physiol 88: 386-392, 2000.
22. Romano B, Todd M, and Saunders M. Effect of a 4: 1 Ratio Carbohydrate/Protein
Beverage on Endurance Performance, Muscle Damage and Recovery. Med Sci
Sports Exc 36: S126, 2004.
23. Romano-Ely B, Todd M, Saunders M, and St. Laurent T. Effect of an Isocaloric
Carbohydrate-Protein-Antioxidant Drink on Cycling Performance. Med Sci Sports
Exc 38: 1608-1616, 2006.
24. Saunders M, Kane M, and Todd K. Effects of a Carbohydrate-Protein Beverage on
Cycling Endurance and Muscle Damage. Med Sci Sports Exc 36: 1233-1238, 2004.
25. Saunders MJ, Luden ND, and Herrick JE. Consumption of an oral carbohydrateprotein gel improves cycling endurance and prevents postexercise muscle damage.
J Strength Cond Res 21: 678-684, 2007.
26. Tipton KD, Borsheim E, Wolf SE, Sanford AP, and Wolfe RR. Acute response of net
muscle protein balance reflects 24-h balance after exercise and amino acid
ingestion. Am J Physiol Endocrinol Metab 284: E76-89, 2003.
27. Valentine RJ, Saunders MJ, Todd MK, and St Laurent TG. Influence of
carbohydrate-protein beverage on cycling endurance and indices of muscle
disruption. Int J Sport Nutr Exerc Metab 18: 363-378, 2008.
28. van Hall G, Shirreffs SM, and Calbet JAL. Muscle glycogen resynthesis during
recovery from cycle exercise: no effect of additional protein ingestion. J Appl Physiol
88: 1631-1636, 2000.
29. Yaspelkis BB, 3rd, and Ivy JL. Effect of carbohydrate supplements and water on
exercise metabolism in the heat. J Appl Physiol 71: 680-687, 1991.
30. Zawadzki KM, Yaspelkis BB, 3rd, and Ivy JL. Carbohydrate-protein complex
increases the rate of muscle glycogen storage after exercise. J Appl Physiol 72:
1854-1859, 1992.