Protein and Muscle Development
The strength-to-weight ratio is critically important in virtually all athletic endeavors, so athletes are rightly interested in ways to improve or sustain muscle mass. Athletes and their coaches commonly believe the central nutrition strategy for achieving this is to increase protein consumption. However, assuming caloric needs are met, the anabolic maximum for protein is reached at an intake level of approximately 1.5 grams of protein per kilogram of mass. Clearly, if there is a relationship between protein consumption and muscle mass, it must be related to other factors including the type of exercise performed relative to the amount and type of protein consumed, the within-day distribution of protein consumed, and the coingestion of protein with other nutrients. There are, of course, also limitations in how well different populations may hope to enhance musculature, even when optimal nutrition strategies are coupled with appropriate resistance activities. Aging reduces the responses of muscle fibers and the anabolic signaling response to resistance exercise. Although few differences exist between the muscular responses of young women and young men to acute exercise, the muscular responses of older women may be blunted more than in older men.
The timed distribution of protein from food within a day has been assessed, with findings that clearly indicate improved muscle maintenance and enlargement when large peaks and valleys in protein consumption are avoided. Findings suggest that 90 grams of protein (enough to provide 1.5 grams per kilogram for a 60-kilogram, or 132-pound, person) was inadequate to sustain muscle mass when the protein intake (from foods) was postloaded so that most of the protein was consumed during the evening meal. However, when the same amount of protein was evenly redistributed to provide an equal amount (30 grams) of protein at each meal (breakfast, lunch, and dinner), the studied population was able to sustain and, in some cases, even increase muscle mass. The timing of nutrient ingestion also influences the anabolic response of muscle after exercise. Amino acid uptake is greater when free essential amino acids and carbohydrate are ingested before rather than after resistance exercise. However, consumption of whey protein (a whole-food protein) increased amino acid balance from negative to positive regardless of whether it was consumed before or after exercise.
There is a common misunderstanding that extra protein intake alone will support a larger muscle mass, and this theory is the main rationale for the large protein intakes seen in many athletes. In fact, additional total calories are required to support a larger muscle mass, and protein should constitute the same relative proportion of the extra calories consumed. For instance, if a 75-kilogram (165 pound) man wishes to increase his muscle mass by 3 kilograms (6.6 pounds), he would need to consume approximately 1.5 additional grams of protein for each kilogram of muscle mass desired. This amounts to only 4.5 grams of additional protein to support the larger muscle mass. By contrast, 30 grams per kilogram of additional carbohydrate, or 90 grams of additional carbohydrate in total, is required to support the larger muscle mass. Here is the total additional caloric requirement represented by the additional muscle:
- 4.5 grams protein × 4 calories per gram = 18 kilocalories from protein
- 90 grams carbohydrate × 4 calories per gram = 360 kilocalories from carbohydrate
- Total additional calories = 378 calories per day above current requirements to support a 3-kilogram increase in muscle mass
Of course, this athlete would also need to stimulate muscle enlargement by undertaking the appropriate strength-building exercises. Otherwise, the extra calories would manifest themselves as stored fat rather than additional muscle. It is likely that the large amount of protein consumed by so many athletes represents the extra calories they require to maintain or enlarge the muscle mass. Although it is certainly possible to use protein as a primary energy source, it is not the most desirable source because of the nitrogenous wastes produced with protein oxidation. In addition, protein can be an expensive source of calories when provided in supplement form. For instance, eggs (an extremely high-quality source of protein) cost approximately 13 cents per 8 grams of protein, while protein capsules cost approximately $1.20 per 8 grams of protein and may be of questionable quality.
The coingestion of protein and carbohydrate has been assessed to determine if this enhances muscular protein update. One study found that trained men who ingested carbohydrate at the upper end of the recommended level to improve endurance performance (about 8 to 10 grams per kilogram) experienced no enhancement in skeletal muscle energy delivery with the addition of protein. On the other hand, when protein was ingested with carbohydrate during recovery from aerobic exercise, it had the effect of increasing muscle synthesis and improving whole-body net protein balance when compared with an equal caloric load of carbohydrate alone. It has also been demonstrated that an inadequate level of carbohydrate intake compromises skeletal muscle protein utilization and synthesis.
To summarize, building muscle involves more than simply increasing protein and amino acid intakes. It involves the following:
- Addition of resistance activity to provide the physiological motivation (stimulation) to enlarge the muscle mass. It appears that low-load, high-volume resistance activity is superior to high-load, low-volume resistance activity in inducing acute muscle development.60
- The maintenance of a sufficient total energy intake to fully satisfy the energy requirement, including the additional requirement of the added resistance activity. The goal is to allow consumed protein to be used for anabolic purposes rather than to be catabolized as a source of energy to help meet energy needs. In addition, it is possible to build muscle only if strategies are followed to reduce muscle breakdown. Sustaining a good energy balance throughout the day helps achieve this goal, enabling an improved potential for muscle building.
- A protein intake of approximately 1.5 grams of protein per kilogram of body mass. With an adequate total energy intake, this level of protein appears to fully satisfy the anabolic requirements of new muscle synthesis.
- A distribution of protein during the day that avoids large peaks and valleys in protein intake. Ideally, the protein consumed should be evenly distributed over multiple meals during the day.
- The consumption of a high-quality protein source (such as whey protein) either before or after exercise. This strategy appears to enhance muscle protein synthesis.
- The consumption of a carbohydrate and protein mixture immediately after exercise. This strategy also appears to enhance muscle protein synthesis. Athletes should avoid consuming only protein after exercise since this is a key opportunity to replenish depleted glycogen stores, and carbohydrate is needed for this purpose.