Muscles need protein to grow, and a steady supply of protein in your diet –1 to 1.5 grams of protein per pound of bodyweight – is a requirement for putting on size. There’s ongoing discussion concerning whether taking a protein supplement immediately prior to, or right after, a weight-training session is best to increase protein synthesis. Increased protein synthesis is important because over the long term, it will result in an increase in muscle mass. Sports science studies involving ingestion of protein immediately prior to or within three hours after a weight-training session show increases in muscle protein synthesis. This increase appears to be related to a more favorable anabolic environment as a result of changes in hormonal concentrations, such as an increase in blood insulin or growth hormone.
Some evidence indicates that protein supplementation immediately prior to exercise increases protein synthesis to a greater extent compared to supplementation at various times after exercise. The increased protein synthesis with supplementation prior to exercise may be related to a boost in blood flow during exercise, which increases amino acid availability to the muscle being trained during the session. With an increase in blood flow, greater delivery of the amino acids from the supplement takes place. With greater delivery of amino acids to the muscle being trained, there’s a possibility that more of these amino acids will be used in the protein synthesis of muscle. An alternative explanation is that protein synthesis is stimulated by exercise due to both an increase in blood flow and an increased hormonal response when a supplement is consumed before exercise. As a result, the stimulation of protein synthesis continues— not just during the exercise session, but after the session as well. When a protein supplement is taken immediately after a training session, there’s little effect of increased blood flow on muscle protein synthesis, and the increase in muscle protein synthesis is more dependent on the hormonal response to the training session. However, one bottom-line aspect of this evidence is that supplementation either before or after a weight-training session will increase muscle protein synthesis.
Additional research indicates that supplementation after a weight-training session increases the androgen receptor content of muscle. Although we spend a great deal of time talking about the hormonal response (such as an increase in testosterone or growth hormone in the blood) because of supplementation and weight training, we tend to forget that hormonal response is only part of what needs to happen to increase protein synthesis. One important aspect of this process is that the hormone needs a receptor within the muscle with which to bind in order to trigger increased protein synthesis. Researchers have shown that supplementation immediately after a weight-training session results in increased androgen receptor content of muscle. This widens the possibility that a hormone circulating in the blood will actually bind to a muscle’s receptor, increasing the chance that the hormone will cause a rise in protein synthesis.