Nutrient interaction for optimal protein anabolism in resistance exercise.

PURPOSE OF REVIEW: The rapid muscle loss that accompanies varying diseased states (cachexia) is due to an imbalance between muscle protein synthesis (MPS) and muscle protein breakdown In the current review, we will discuss and summarize recent evidence in order to provide practical recommendations on exercise and nutrient interventions for cachectic populations.

RECENT FINDINGS: Resistance exercise is a potent stimulus for MPS, but cachexia patients may not be best placed to lift the heavy loads that, it was previously assumed, were a prerequisite for muscle hypertrophy. However, recent evidence from our lab shows that lower loads can effectively stimulate MPS and lead to hypertrophy. Protein ingestion potentiates resistance exercise-induced rates of MPS. The source and dose of the ingested protein are important to consider when attempting to maximize postresistance exercise MPS. Specifically, rapidly digested, leucine-rich protein sources may stimulate greater postexercise rates of MPS than other protein sources, as leucine acts as a key anabolic signal for mRNA translation. Furthermore, individuals undergoing relatively slow muscle atrophy (i.e., in sarcopenic elderly) respond positively to larger doses (40  g) of amino acids following exercise, whereas the response appears to plateau after moderate doses (20  g) in healthy, young adults.

SUMMARY: Emerging evidence shows that manipulating traditional exercise loading and nutrient strategies may ameliorate cachexia.