Quick Hit Summary
The restoration of glycogen stores is the primary focus of post workout nutrition for the endurance athlete. Additionally, you want to supply your body with protein to maximize muscle recovery. If one is living by scientific studies alone, it appears that 0.55 g CHO/lb and 0.08 g PRO/lb (1.2 g CHO/kg and 0.18 g PRO/kg) within 15-30 minutes following an intense aerobic workout to maximize recovery. For reference, this would be ~90 g CHO and 13 g of PRO for a 165 lb individual. This should be repeated ~60- 90 minutes later. However, based off practical application, I have found that a 2:1 to 4:1 ratio of Carbs to Protein works fine immediately following a workout (often in a shake) and followed up again in meal based form within the following 90 minutes. Don’t worry, consuming protein won’t cause you to get “bulky.” Rather than build up large muscles (as seen in bodybuilding or power lifting), endurance training increases the synthesis of proteins related to energy production (ie- mitochondria). Thus, your body is more capable of running at a higher intensity during subsequent training sessions.
Post-workout Nutrition for Endurance/Aerobic Athletes
Is your post workout nutrition measuring up?13
Previously, I discussed the importance of nutrition during the first few hours following an exercise session. In addition, I laid out specific nutrition recommendations for endurance athletes. For those who have not already done so, I strongly recommend reading Post Workout Nutrition as it will serve as the backdrop for the recommendations made here.
Due to the large loss of glycogen during endurance/aerobic training, my main focus is restoring glycogen levels between workouts. In the process, one will also go from a catabolic to anabolic environment, supporting muscle growth and repair. As we’ll see, this is best accomplished by ingesting both carbohydrates and protein following a training session. Together these macronutrients increase the release of the anabolic hormone insulin, decrease the release of the catabolic hormone cortisol and replenish glycogen stores. Furthermore, insulin, in the presence of amino acids, appears to support protein synthesis, allowing damaged tissue to be repaired1. With that as a backdrop, let’s get down to the four key elements of the post workout meal/shake that endurance athletes must consider: timing, amount, type of carbohydrate and protein.
Timing
Multiple Training Sessions/Day
Quickly replenishing muscle glycogen stores have important consequences for endurance athletes competing in multiple exercise sessions/day (ie- marathon or triathlon training). In a landmark study completed in 1988, Ivy et al. demonstrated that the body had an enhanced ability to replenish glycogen stores with dietary carbohydrates if consumed shortly after exercise2. In their study, 12 experienced male cyclist (mean age- 26 years) completed 2 separate glycogen depleting endurance workouts. After each trial participants received either a placebo or carbohydrate drink that was proportional to the body weight of the individual (2g/kg of bodyweight). Two hours later individuals once again drank the beverages except those who consumed the placebo initially, now took the carbohydrate drink. A week later the same procedure was repeated except participants drank the beverages in reverse order. Ivy et al found some interesting results…Compared to waiting 2 hours to take the carbohydrate drink, results indicated that immediate consumption resulted in a 300% increase in muscle glycogen at 2 hours and a 135% increase at 4 hours.
Single Training Session/Day
For those who have 24 hours of “rest” between training sessions and receive adequate carbohydrates over the course of a day (6-12g CHO/kg of bodyweight), immediate consumption of carbohydrates does not seem quite as important with respect to replenishing glycogen stores. This was demonstrated by Parkin et al. who examined the influence of various meal patterns on glycogen replenishment following 2 intense training workouts followed3. Following the 2 separate glycogen depleting workouts, each athlete ate 5 meals over a 22 hour time span. The meals consisted of 2.5 g of carbohydrates/kg of bodyweight; protein and fat content were also matched for bodyweight. The protocol differed only in the timing of the first meal. Following one of the sessions, participants received the first meal immediately following the workout (remaining meals consumed at 2, 4, 8 & 22 hrs post exercise). Upon completing the other glycogen depleting workout, the first meal wasn’t consumed until 2 hours following the termination of exercise (remaining meals consumed 4, 6, 8 & 22 hrs post exerercise). Glycogen samples that were obtained 8 and 24 hours upon completion of each workout revealed that timing of the meals had no impact on replenishing muscle glycogen stores.
Amount of Carbohydrate
Besides timing, one must also consider the amount of carbohydrate required to optimize recovery. Ivy et al. had 8 individuals complete multiple glycogen depleting workouts4. Participants consumed either 1.5g or 3.0g of carbohydrates/kg of body weight immediately and then again 2 hours after each workout. Regardless of the amount of carbohydrates consumed, glycogen stores were the same when measured 4 hours post-exercise. In a separate study, van Loon et al. demonstrated that consuming carbohydrate in the amount of 1.2g/kg of bodyweight/hr during the first 4 ½ hrs results in significantly greater rates of glycogen replenishment than 0.8g/kg/hr5. When comparing the mean averages for each group after 5 hours, it was found that taking the higher carbohydrate supplement resulted in glycogen content 133% greater than that of the lower carbohydrate supplement group. To the best of my knowledge, no studies have revealed that amounts greater than 1.2g/kg/hr are more beneficial at replenishing glycogen stores.
Type of Carbohydrate
A carbohydrate’s glycemic index may also impacts the rate at which glycogen stores are replenished. As discussed in an earlier article, Glycemic Index 101, the GI measures the rate at which carbohydrates, obtained via dietary sources, are absorbed from the digestive track and enter the bloodstream. Since increasing blood glucose levels stimulate insulin release, many researchers have pondered if the GI of a given food influences the rate at which glycogen stores are refilled. Burke et al. attempted to answer this question by giving 5 elite junior cyclist (mean age- 18 years) 4 high or low GI meals following 2 glycogen depleting exercise sessions6. Participants ate 4 meals at the following time intervals: 0 (immediately), 4, 8, and 21 hours after each workout. The amount of carbohydrate in each meal was individualized such that participants consumed 2.5g/kg of bodyweight. Overall, the macronutrient content of each meal was 74% carbohydrate, 11% fat and 15% protein. At 24 hours post workout, it was found that when consuming the high glycemic meal, individuals had significantly greater muscle glycogen stores. Interestingly, no significant differences in serum glucose or insulin levels were found following the meal consumed closest to the exercise session. Despite this, high GI foods are recommended post-exercise.
Protein & Carbohydrates
Ivy et al. have also compared the effects of taking drinks of various macronutrient profiles on refueling glycogen stores9. In a study that included 7 trained men (mean age- 23 years), their research team had athletes complete 3 separate endurance trials. After each trial, participants received 2 beverages; each was drunk at 10 and 120 minutes following the completion of their endurance trials. Rather than individualizing the supplements based off bodyweight, every individual received the same supplements. The nutrition profile of each beverage was as follows:
- Carbohydrate+Protein (CHO+PRO): 378 kcal- 80 g CHO, 28g PRO, 6g Fat
- High Carbohydrate (HCHO): 378 kcal- 108g CHO, 6g Fat
- Low Carbohydrate; served as control beverage (LCHO):294 kcal- 80g CHO, 6g Fat
{If curious what the individualized amounts would be, the mean weight for the group was 74 kg (1 kg= 2.204 lbs; therefore 74kg = 163 lbs) and sizes ranged from 70-82 kg. Taking the individualized CHO+Pro for the lightest weight person, this would come out to 1.14g CHO/kg/hr, 0.4g PRO/kg/hr, and 0.09g fat/kg/hr}.
Ivy et al. measured muscle glycogen content at 40, 120, and 240 minutes post-exercise9. At 240 minutes, CHO+PRO was superior at restoring muscle glycogen in comparison to the other treatments. The most pronounced difference in glycogen replenishment occurred during the first 40 minutes where almost 2x as much glycogen was restored in the CHO+PRO vs. HCHO and 4x as much vs. LCHO.
Protein + Carbohydrates is Best Refueling Strategy
It appears that one can take a couple of different approaches to quickly refuel glycogen stores. Based off research, one can consume high amounts of carbohydrates (1.2g/kg of bodyweight/hour) more frequently and not worry about protein8. On the other hand, one can take CHO+PRO combination at less frequent intervals to quickly replenish glycogen stores9.
Of the two options presented, CHO+PRO is the far superior choice. One must not forget, the purpose of the post workout recovery is to optimize both glycogen replenishment AND muscle recovery. Science has clearly proven that a CHO+PRO drink is superior to a CHO only drink at muscle repair. In a recently published study published by Howarth et al., 6 active men (mean age- 22 years) took part in 3 separate endurance cycling trials10. Following each trial they took 1 of 3 drinks every 15 minutes for 3 hours. The nutrition profile of each individualized beverage was as follows:
- Carbohydrate +Protein (CHO+PRO): 1.2 g CHO/kg/hr + 0.18 g PRO/kg/hr
- High Carbohydrate (HCHO): 1.6 g CHO/kg/hr
- Low Carbohydrate; served as control beverage (LCHO): 1.2 g CHO/kg/hr
The authors chose to use a high glycemic CHO source, Maltodextrin, and a fast absorbing protein source, hydrolyzed whey protein (from concentrate), to maximize the post-exercise recovery.
Results of the study indicated that taking the CHO+PRO significantly enhanced protein synthesis compared to the other two options. This enhanced protein synthesis occurred despite it being isocaloric with the high CHO beverage.
Will Protein Make me “Bulky”?
Many endurance athletes fear getting “bulky” from consuming protein supplements. However, post workout protein will not cause a lean endurance athlete to morph into the Incredible Hulk!!! Due to the training principle of specificity, muscles adapt differently to endurance training than they do resistance training11. Wilkinson et al., found that following resistance training, protein synthesis was more geared towards increasing muscle size12. In contrast, following endurance training, protein synthesis contributed more towards producing proteins structures (ie-mitochondria) associated with improved endurance performance.
Although it wasn’t the primary focus of their article, Howarth et al., also found that no difference in muscle glycogen restoration was present between treatment groups12. This is in agreement with previous research that demonstrated that 1.2g CHO/kg/hr maximized glycogen recovery8.
Study Caveats
A couple caveats should be mentioned with the studies presented here in this article. First, most of the studies were completed following an overnight fast. If competing endurance training of higher intensity, it’s commonly recommended to have food in your stomach prior to competing. Also due to being in a fasted state, rates of glycogen replenishment, etc, were faster than what they’d be if someone had eaten within the previous few hours. The second point that I’d like to make is that almost all the studies were completed in male subjects. Due to hormonal discrepancies, different results may have been seen in a female population. My intention was not to exclude studies with female participants. Rather, there’s just a lack of research on post-workout nutrition in the female population.
Recommendations
Based off research presented here, it appears that one should consume 1.2 g CHO/kg/hr and 0.18 g PRO/kg/hr following an intense aerobic workout. It’s important to not only consume foods shortly after exercising, but also to make sure the foods that you’re eating can quickly be digested. Thus, the carbohydrate should be of a high GI. This can come from either a whole food source with a high GI CLICK HERE for GI Food Chart or easy to mix powders such as maltodextrin. It’s recommended that the protein be from a source that can be quickly absorbed such as hydrolyzed whey protein. The first “meal/beverage” should be consumed within the first 15-30 minutes. At approximately 1½-2 hrs later, repeat this process.
However, based off practical application, I have found that a 2:1 to 4:1 ratio of Carbs to Protein works fine immediately following a workout (often in a shake) and followed up again in meal based form within the following 90 minutes. Usually this is something like 20 grams protein, 40-80 grams carbohydrates depending on the intensity of the workout.
Bottom Line
The main goals of post-workout nutrition are to create an anabolic environment within one’s body to support tissue growth. In the process of accomplishing the first goal, one will often achieve the second goal; replenishing glycogen stores.
If you’re going to work hard training, be smart and refuel your body afterwards!
References
1 Wolfe RR. Effects of insulin on muscle tissue. Curr Opin Clin Nutr Metab Care. 2000 Jan;3(1):67-71.
2 Ivy JL, Katz AL, Cutler CL, Sherman WM, Coyle EF. Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. J Appl Physiol. 1988 Apr;64(4):1480-5.
3 Parkin, J.A.M., Carey, M.F., Martin, I.K., Stojanovska, Land Febbraio, M.A. (1997). Muscle glycogen storage following prolonged exercise: effect of timing of ingestion of high glycemic index food. Medicine and Science in Sports and Exercise, 29, 220–224.
4 Ivy JL, Lee MC, Brozinick JT Jr, Reed MJ. Muscle glycogen storage after different amounts of carbohydrate ingestion. J Appl Physiol. 1988 Nov;65(5):2018-23.
5 van Loon LJ, Saris WH, Kruijshoop M, Wagenmakers AJ. Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures. Am J Clin Nutr. 2000 Jul;72(1):106-11.
6 Burke LM, Collier GR, Hargreaves M. Muscle glycogen storage after prolonged exercise: effect of the glycemic index of carbohydrate feedings. J Appl Physiol. 1993 Aug;75(2):1019-23.
7 Blachier F, Leclercq-Meyer V, Marchand J, Woussen-Colle MC, Mathias PC, Sener A, Malaisse WJ.Stimulus-secretion coupling of arginine-induced insulin release. Functional response of islets to L-arginine and L-ornithine. Biochim Biophys Acta. 1989 Sep 19;1013(2):144-51.
8 Jentjens RL, van Loon LJ, Mann CH, Wagenmakers AJ, Jeukendrup AE. Addition of protein and amino acids to carbohydrates does not enhance postexercise muscle glycogen synthesis. J Appl Physiol. 2001 Aug;91(2):839-46.
9 Ivy JL, Goforth HW Jr, Damon BM, McCauley TR, Parsons EC, Price TB.Early postexercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement. J Appl Physiol. 2002 Oct;93(4):1337-44.
10 Howarth KR, Moreau NA, Phillips SM, Gibala MJ. Coingestion of protein with carbohydrate during recovery from endurance exercise stimulates skeletal muscle protein synthesis in humans. J Appl Physiol. 2009 Apr;106(4):1394-402. Epub 2008 Nov 26.
11 Coffey VG, Hawley JA.. The molecular bases of training adaptation. Sports Med. 2007;37(9):737-63.
12 Wilkinson SB, Phillips SM, Atherton PJ, Patel R, Yarasheski KE, Tarnopolsky MA, Rennie MJ. Differential effects of resistance and endurance exercise in the fed state on signaling molecule phosphorylation and protein synthesis in human muscle. J Physiol 586: 3701–3717, 2008.
13 Photo by kteague. Accessed June 14, 2010 from: flickr.com/photos/49503205198@N01/3335735763