After an intense resistance training protocol, athletes subject their muscles and connective tissue to intense levels of damage and stress. This process is a necessary part of the process of strength development and hypertrophy. The benefits of immediate PWO protein supplementation are well documented (3,5,8-11,13-15,17-19,21-23). The activated skeletal muscle sustains significant microtrauma and may remain in a catabolic (tissue breakdown) state for some time after the workout. Providing muscles with the necessary protein after resistance training has a great impact on the accumulation of skeletal muscle protein, which leads to proper repair and growth of muscle tissue. The purpose of this article is to address various protein supplementation techniques used to induce the maximal recovery effect and minimize recovery time between workouts.
DIFFERENT APPROACHES AND RESEARCH
A review of the literature on PWO protein supplementation reveals a vast quantity of applicable data. Some data on protein supplementation support the conclusion that protein supplementation is not necessary for athletes because the body is able to adapt and use available protein more efficiently after the initial phases of training (20,23). These data generally are based on daily protein requirements versus immediate PWO protein consumption and focus on maintaining net protein balance rather than increasing protein synthesis. There are many more studies, however, in which PWO protein supplementation is shown to be a vital part of any athlete's diet (3,5,8-11,13-15,17-19,21-23). It is likely that any individual trying to build muscle and enhance recovery should make every effort to maintain a positive protein balance throughout the day and especially after training. Three different methods of protein supplementation that one might consider to help maintain this balance are whole food, protein powders/pills, and amino acid (AA) supplements.
WHOLE FOOD PROTEINS
The most basic method is the whole food approach. Any additional dietary protein would come from a food source such as meat, eggs, or milk. Supplementing with whole food proteins is relatively cost effective and can generally be considered safe, as long as the food source is not overly processed. Foods such as microwave meals, hot dogs, and canned goods usually are overly processed and cannot always be considered as healthy protein sources. Proteins from whole food sources are rich in most AAs and micronutrients and effectively create the necessary surplus of calories and AAs. They also take longer to digest, which allows for a steadier stream of AA delivery to the muscle. If these proteins are consumed as part of a meal, the additional macronutrients (carbohydrates and fats) can assist in muscle recovery. A down side is that cooking is time consuming and requires some planning.
A few whole foods are worth mentioning because their relatively high protein content. Fish has an AA profile rich in glutamic acid and lysine. Glutamic acid is a precursor to glutamine, which has been shown to enhance PWO glycogen restoration (6). Cold water species such as tuna and salmon also contain omega-3 fatty acids, which are quite valuable to the athlete in training because of their antiinflammatory properties. Beef also is an excellent source of protein. Beef is a perfect complement to the athlete's diet because it is rich in zinc and iron and contains a high amount of protein that is rich in essential AAs (EAAs). Although the AA profile of beef is considered superior, it has a protein digestibility corrected AA score (PDCAAS) of 0.92 based on its reduced digestibility. Chicken, arguably the most versatile and popular meat for athletes, is also a high-quality protein source because it is rich in EAAs. Eggs and egg whites are another popular addition to the athlete's diet. Each egg white equals about 5 grams of pure protein and eggs score a PDCAAS of 1.0, which is the highest score attainable. Whole eggs are rich in B vitamins, vitamin D, vitamin E, and phosphorus. The AA profile of eggs is ideal as they are rich in both branched chain AAs (BCAAs) and glutamic acid. Boiled eggs are a convenient protein source for an athlete that must travel frequently. Skim milk, or even chocolate milk, shows much promise as a PWO beverage. Milk protein consists of both whey and casein, and milk (especially chocolate) contains necessary carbohydrates that facilitate PWO glycogen restoration (13,14,22). Also, the AA profile of milk is quite robust and facilitates muscle recovery well because it is rich in glutamic acid and BCAAs. Although it is unlikely that regular consumption of a single protein source is harmful to performance, it seems reasonable that the complementary nature of a variety of proteins is the most effective approach.
The use of commonly available commercial protein powder supplements is now a popular and convenient method of increasing protein intake, especially in the PWO role. There are many different types of protein supplements, and they differ in source and content. Most of the modern protein supplements are whey varieties. Whey protein is isolated from milk protein and is different from milk's primary protein, casein. It is inexpensive to produce, and it is high in BCAAs and glutamic acid. Whey is regarded as one the highest-quality proteins based on its ideal AA profile (rich in necessary EAAs) and it is high digestibility, giving it a PCDAAS of 1.0. Whey protein comes in different varieties, as well: concentrate, isolate, and hydrolyzed. All are high-quality proteins. The differences among the 3 are based on the amount of processing involved and the amount of protein per gram. Whey concentrate is the least processed and has the least available protein. Whey isolate is processed more to increase the amount of protein and remove impurities. Hydrolyzed whey is predigested by enzymes, breaking the protein molecules into smaller peptides. This allows the protein to rapidly enter the bloodstream. This quick assimilation rate is a major benefit of whey protein in general. The AAs are quickly broken down by the digestive system and released into the blood for use by muscles, which can also be a problem. Some research suggests that when AAs flood the blood stream too quickly, the muscles cannot use them fast enough (22). The result is that they can be stored as fat, converted to glucose for energy, or broken down and excreted. With whey, smaller doses may be more cost effective and help prevent wasteful consumption.
Other types of protein powder supplements include casein derivatives, soy, egg white protein, hydrolyzed wheat protein, and even beef protein. Casein is the main protein found in milk and has been effectively shown to be a superior source of protein. Casein releases the AAs into the blood stream much slower than whey, and thus keeps a steady flow of AAs for a longer period of time. Many protein manufacturers are now blending whey and casein to provide a powder that contains both fast and slow acting proteins. Current research supports the conclusion that this is the best approach to PWO protein supplementation (22).
Soy protein has increased in popularity over the last 2 decades. It is a high-quality protein (PDCAAS of 1.0), despite being a plant source protein. An interesting fact about soy protein is that it contains isoflavones, specifically phytoestrogens. Isoflavones are antioxidants and show much promise in preventive medicine (16). However, many believe that high doses of soy protein in men may have the undesirable effect of increasing estrogen, leading to negative side effects (especially for the weight trainer or strength athletes), although this assertion has not been conclusively proven at the time of this writing (7). Soy has an AA profile similar to that of milk and may be used as an alternative, if necessary. Studies that compare soy and milk products generally show that milk is the superior protein for muscle repair, although soy protein continues to show some promise based on its antioxidant properties and AA profile (13,22).
Egg white (albumin) protein has long been considered the “gold standard” of protein. It is one of the highest quality proteins available, and it is easily digestible. As a supplemental powder, egg white protein is probably slightly less effective than real egg whites, as the result of processing and shelf life. Nonetheless, it is still a high-quality protein.
Hydrolyzed wheat protein and buckwheat fraction protein, although not as popular as whey, are commercially available proteins that have limited proven efficacy. Studies show that, in trained cyclists, a solution containing wheat hydrolysate with added leucine and phenylalanine elicited a plasma insulin response greater than double that of carbohydrates alone. The researchers discovered that the addition of leucine and phenylalanine was critical to the high insulin response (21). Wheat hydrolysate alone may have very limited use as it is lacking in both lysine and tryptophan.
Beef protein supplements are becoming less and less popular, although they are still commercially available. Most are sold as desiccated (dried out) liver tablets or powder in protein blends. It is rare to find a beef protein powder now, but they are still around. Most strength and conditioning coaches can adequately supplement their athletes' diet without the need for beef protein supplements. Desiccated beef tablets may be considered if the athlete's schedule does not allow time for a proper diet, as they can be carried and taken throughout the day. They still carry many of the micronutrients contained in whole beef, as well.
Finally, another protein source clings to the market and disguises itself in well marketed ingredient lists. Hydrolyzed collagen is a poor source of protein for muscle growth and repair. It has a low PDCAAS score and it is low in AAs like the BCAAs and glutamic acid and is deficient in some essential AAs. Collagen protein is high in the AAs proline and glycine, which make it suitable for connective tissue repair, although a protein rich diet will supply these AAs in abundance. It is sometimes added to other protein sources as an inexpensive way to boost the volume of a protein powder, pill, or liquid. Care must be taken when reading protein supplement labels. Better forms of protein are not much more expensive and are generally a far better source than collagen.
AA supplements show great efficacy in increasing protein synthesis. These supplements contain varying amount of either EAAs, or a combination of EAAs and nonessential AAs (NEAAs). Research conducted by Tipton et al. (17) in 1999 showed that EAA mixtures elicit a high corresponding rate of muscle protein synthesis, equal to that of other proteins; the researchers concluded that NEAA were not necessary to elicit this response.
Taking individual AAs alone or with an additional protein source may also be an effective PWO technique. According to recent research, specific AAs added to PWO supplements, specifically protein supplements, show potential to elicit independent effects. For example, proteins with high levels of leucine, BCAAs, or glutamine are more ideal for muscle building and recovery. Leucine, for example, induces a significant increase in insulin, even when compared with a carbohydrate feeding (1,4,9,10-12,21). Insulin helps shuttle proteins into the muscle and higher levels of insulin generally correspond to reduced levels of protein degradation (10). Consequently, proteins with high levels of leucine facilitate an increase in net protein balance. The addition of BCAAs can reduce the need for PWO carbohydrates, as the BCAAs are available for conversion into glucose (11). This might lead to more protein utilization for the hypertrophy process. Glutamine, the most abundant AA in the human body, has been shown to increase the post exercise storage of glycogen (6). These AAs are all present in high quality proteins, but the addition of the individual AA(s) can alter the AA profile and, in effect, create an “engineered” protein that may be of greater benefit to a strength athlete than a naturally occurring protein.
CONCLUSION: THE FINAL PIECE OF THE PUZZLE
Faced with all these data, strength and conditioning coaches must choose a protein that will yield maximal results with the least preparation time and cost. The reality is that there is no “magic bullet” for PWO protein supplementation. Many protein sources are adequate and most proteins, whether supplement or whole food, will yield some results. The question is, “will it yield the best results?”
First, the selection of the protein should be a deliberate process. Check the ingredients label on supplements to ensure that the proteins are derived from quality sources, such as whey, egg, and/or casein. Some protein manufacturers will claim superior proteins on the label but provide a minuscule amount of true high-quality protein complimented by a majority of lower quality proteins. Some powder supplements also contain additional ingredients, such as creatine, fats, carbohydrates, vitamins, and botanicals that may or may not be a desired addition to the athlete's diet. An important factor might also be taste. If the athletes don't like the taste, they may be reluctant to drink or take the supplement. Hydrolyzed whey, for example, has an extremely bitter taste and despite its high quality is a hard supplement to swallow.
Optimally, the PWO protein should be of high quality and it should contain a mix of fast and slow digesting proteins (22). A protein powder containing milk protein is a sound choice because of milk's favorable AA profile and digestibility factors (except in the lactose intolerant population). Additionally, added AAs can increase the effectiveness of any protein and might be a consideration. Many protein supplements have added AAs already (leucine, glutamine, arginine, and BCAAs are popular additions), so they may be adequate for PWO needs. Whole foods are a viable solution for PWO protein also, and foods such as turkey sandwiches, boiled eggs, and chicken breasts can all be prepared ahead of time and stored for PWO consumption.
How much PWO protein does an athlete need? Unfortunately, some of the most recent studies used intravenous bolus injections of AAs, making application difficult, but others studied the effectiveness of oral protein and/or AA ingestion in the PWO role. One study reported a significant increase in protein synthesis with a modest oral dose of 6 g of EAA, whereas another study reported similar results with a dose of 40g of protein (15,17). PWO protein benefits appear to be dose independent and 6-40 g of protein will induce similar effects on protein synthesis (15,17,23). As long as the athlete's daily protein requirements are met, the PWO dose does not need to be large.
Coaches, strength and conditioning coaches, and athletes must become accustomed to the habit of immediate PWO nutrition. The act of consuming the PWO meal or shake must be considered part of the workout. They must know that the sooner the supplement is consumed after the workout the better the results will be. Current data further shows that pre-workout and during-workout protein supplementation yields significant increases in protein synthesis rates (2,19).
Providing athletes with a sound PWO protein strategy involves supplying adequate sources of protein and dedication to the PWO supplementation program. Coaches and strength and conditioning professionals should take an active interest in what their athletes are consuming (or not) after their workouts, as this critical window is the keystone to the productivity of the next workout. A well-rounded PWO protein program is equally as important as the training program, and the failure to adhere to a PWO nutrition program based on sound, proven principles can hinder performance at all levels of competition.
1. Anthony JC, Anthony TG, and Layman DK. Leucine supplementation enhances skeletal muscle recovery in rats following exercise. J Nutr
129: 1102-1106, 1999.
2. Beelen M, Koopman R, Gijsen AP, Vandereyt H, Kies AK, Kuipers H, Saris WHM, and van Loon LJC. Protein coingestion stimulates muscle protein synthesis during resistance-type exercise. Am J Physiol Endocrinol Metab
295: E70-E77, 2008.
3. Bolster DR, Pikosky MA, Gaine PC, Martin W, Wolfe RR, Tipton KD, Maclean D, Maresh CM, and Rodriguez NR. Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise. Am J Physiol Endocrinol Metab
289: E678-E683, 2005.
4. Borsheim E, Cree MG, Tipton KD, Elliot TA, Aarsland A, and Wolfe RR. Effect of carbohydrate intake on muscle protein synthesis during recovery from resistance exercise. J Appl Physiol
96: 674-678, 2004.
5. Borsheim E, Tipton KD, Wolf SE, and Wolfe RR. Essential amino acids and muscle protein recovery from resistance exercise. Am J Physiol Endocrinol Metab
283: E648-E657, 2001.
6. Bowtell JL, Gelly K, Jackman ML, Patel A, Simeoni M, and Rennie MJ. Effect of oral glutamine
on whole body carbohydrate storage during recovery from exhaustive exercise. J Appl Physiol
7. Dillingham BL, McVeigh BL, Lampe JW, and Duncan AM. Soy protein isolates of varying isoflavone content exert minor effects on serum reproductive hormones in healthy young men. J Nutr
135: 584-591, 2005.
8. Ivy JL. Regulation of muscle glycogen repletion, muscle protein synthesis and repair following exercise. J Sports Sci Med
3: 131-138, 2004.
9. Koopman R, Pannemans DLE, Jeukendrup AE, Gigsen AP, Senden JMG, Halliday D, Saris WHM, van Loon LJC, and Wagenwakers JM. Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise. Am J Physiol Endocrinol Metab
287: E712-E720, 2004.
10. Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM, Gorselink M, Keizer HA, and van Loon LJ. 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-E653, 2005.
11. Millward DJ, Layman DK, Tome D, and Schaafsma G. Protein quality assessment: impact of expanding understanding of protein and amino acid needs for optimal health. Am J Clin Nutr
87(Suppl): 1576S-1581S, 2008.
12. Norton LE and Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr
136: 533S-537S, 2006.
13. Phillips SM, Hartman JW, and Wilkinson SB. Dietary protein to support anabolism with resistance exercise in young men. J Am Col Nutr
24: 134S-139S, 2005.
14. Rankin JW, Goldman LP, Puglisi MJ, Nickols-Richardson SM, Earthman CP, and Gwazdauskas FC. Effect of post-exercise supplement consumption on adaptation to resistance training. J Am Col Nutr
23: 322-330, 2004.
15. 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.
16. Setchell KD and Cassidy A. Dietary isoflavones: Biological effects and relevance to human health. J Nutr
129: 758S-767S, 1999.
17. Tipton KD, Ferrando AA, Phillips SM, Doyle D, and Wolfe RR. Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol
276: E628-E634, 1999.
18. Tipton KD, Blake BR, Miller SL, Wolf SE, Owens-Stovall SK, Petrini BE, and Wolfe RR. Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab
281: E197-E206, 2001.
19. Tipton KD, Elliot TA, Cree MG, Aarsland AA, Sanford AP, and Wolfe RR. Stimulation of net muscle protein synthesis by whey protein ingestion before and after exercise. Am J Physiol Endocrinol Metab
292: E71-E76, 2007.
20. Todd KS, Butterfield GE, and Calloway DH. Nitrogen balance in men with adequate and deficient energy intake at three levels of work. J Nutr
114: 2107-2118, 1984.
21. Van Loon LJ, Kruijshoop M, Verhagen H, Saris WH, and Wagenmakers AJ. Ingestion of protein hydrolysate and amino acid-carbohydrate mixtures increases postexercise plasma insulin responses in men. J Nutr
130: 2508-2513, 2000.
22. Wilkinson SB, Tarnopolsky MA, MacDonald MJ, Macdonald JR, Armstrong D, and Phillips SM. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. Am J Clin Nutr
23. Wolfe RR. Protein supplements and exercise. Am J Clin Nutr