The Role of Protein in Exercise Recovery

Some of the implications of the ACSM/ADA/DC Position Statement are that:

  • Individual protein requirements may be influenced by the size of an athlete as well as the demands of his/her sport (i.e., whether the sport is mainly "endurance"- or "strength"-oriented).

For example, a 132-pound cross-country runner might require 70 to 85 g of protein per day, whereas a 220-pound football player might require up to 160 to 170 g of protein daily.

  • Athletes require 10 to 15 percent of their daily energy intake from protein, provided that sound nutritional practices are followed and energy intake is sufficient to maintain body weight. If, for example, an athlete consumes 3,000 kcal and 10 percent of those calories are from protein. That's enough to provide 75 g of protein (3,000 x 0.10 / 4 kcal per gram of protein).
  • Athletes can meet their protein requirements through diet alone, without the aid of protein or amino-acid supplements, as the typical North American diet is rich in protein-containing foods. The exceptions to this recommendation are athletes who are restricting energy intake in order to lose body weight.

Under those circumstances, a special effort should be made to consume foods (e.g., meat, fish, eggs) and beverages (e.g., milk) that contain ample amounts of high-quality proteins. Vegetarian athletes should also monitor their food choices carefully. 

  • Recovery from strength/resistance exercise

    Heavy resistance exercise increases the rates of both protein synthesis and breakdown in muscle for at least 24 hours after a workout. Unless a protein-containing meal is consumed during recovery, breakdown will exceed synthesis, resulting in the loss of muscle mass.

    Studies (Tipton KD, Wolfe RR. (2004). Protein and amino acids for athletes. J Sports Sci. 22:65-79; Rasmussen RB, Phillips SM. (2003). Contractile and nutritional regulation of human muscle growth. Exerc. Sport Sci. Rev. 31:127-131.) have shown:

  • The amount of dietary protein needed to stimulate muscle recovery is surprisingly small, only 5 to 10 grams of amino acids (that's only 20 to 40 kcal of protein).
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  • Essential amino acids are superior to non-essential amino acids for stimulating muscle growth. Foods such as fish, meat, eggs, and milk are rich in essential amino acids.
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  • The "maximum effective dose" of amino acids (i.e., the single serving size that will maximally stimulate muscle protein accretion) is not known, however, one study showed that the amount of muscle protein gained was similar when subjects consumed 20 to 40 g of essential amino acids after weightlifting exercise. (Tipton KD, Ferrando AA, Phillips SM, Doyle D Jr, Wolfe RR. (1999). Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol Endocrinol Metab 276:E628-E634.)
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  • Thus, there seems to be a point of amino acid availability above which no further stimulation of muscle protein synthesis occurs. This suggests that consuming massive single doses of protein in hopes of further accelerating muscle growth (as often practiced by strength athletes) is futile.
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  • The anabolic boost stimulated by a single dose of amino acids is transient and lasts only one to two hours. This means that ingesting repeated small doses of protein during recovery may be more effective in optimizing the rate of muscle protein gain, as opposed to eating just one large meal.
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  • Carbohydrate added to a protein mixture does not markedly affect the muscle anabolic response, but does confer other benefits, most important being the resynthesis of muscle glycogen.
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