ABSTRACT
The introduction of amino acids into the body, by either oral ingestion or infusion, rapidly increases muscle protein synthesis, while the impact on muscle protein breakdown is less robust (Biolo et al. 1997). In a somewhat similar fashion, acute bouts of resistance exercise while fasted also stimulate increases in muscle protein synthesis, but if no source of carbohydrate or protein is provided, the net balance of muscle protein will remain negative (muscle protein breakdown > muscle protein synthesis) (Phillips et al. 1997). This response occurs because of a rise in muscle protein breakdown that surpasses the rate of muscle protein synthesis (Biolo et al. 1995). When resistance training is completed and an amino acid source is ingested (or infused) in close temporal proximity, the net protein balance becomes positive (muscle protein synthesis > muscle protein breakdown) (Biolo et al. 1997; Tipton, Ferrando, et al. 1999). This research has led investigators to feverishly examine the impact of postexercise feeding to promote a positive balance of muscle protein, a topic outlined in Chapter 10 of this text.
