Post-exercise Recovery After Dietary Protein Ingestion in Healthy Young Men

INTRODUCTION AND RATIONALE

Resistance exercise and protein ingestion can act separately and synergistically to stimulate muscle protein synthesis rates. This synergy of muscle contraction and protein ingestion provides the basis for training-mediated hypertrophy. Many workers have manipulated post-exercise feeding paradigms in an attempt to define the 'optimal' protein source to consume to support muscle protein accretion. Original work was performed using intravenous infusion of mixed amino acids or bolus ingestion of mixtures of crystalline amino acids; however, consuming free amino acids rarely occurs in normal dietary situations. Currently, there has been a great deal of interest in studying the capacity of dairy proteins to stimulate post exercise muscle protein synthesis rates and promote training-mediated hypertrophy. Dairy proteins represent an attractive protein source for researchers to study because they are rapidly digested/absorbed and contain a high proportional of essential amino acid, especially leucine. Both of these characteristics, speed of digestion/absorption and peak amplitude in leucinemia, are fundamental for the maximal stimulation of muscle protein synthesis rates after protein ingestion. However, very little is known about the effects of other types of high-quality animal proteins, such as beef, on stimulating post-exercise muscle protein synthesis rates. Beef is considered a high-quality and widely consumed protein source. Importantly, a 113-g serving of beef contains 30 g of protein (~10 g essential amino acids; ~2 g leucine) and is similar in amino acid composition to that of milk proteins. Certainly, some evidence suggests that the synergistic effect of exercise and feeding on muscle protein synthesis rates is still apparent after consumption of beef. However, the workers did not compare this response to a group that consumed an alternative high-quality isonitrogenous-matched animal-derived protein source. As a result, it can only be speculated on the capacity of beef to stimulate muscle protein synthesis rates as compared to milk proteins during post exercise recovery.

In the present study, we wish to determine the impact of single meal-like amount of minced beef or dairy milk on digestion and absorption kinetics and post exercise muscle protein synthesis rates. This study will be the first to directly compare two commonly consumed protein-rich food items on muscle protein synthesis rates in healthy young men. This information will be highly relevant for developing nutritional interventions for maintaining and accruing muscle mass.

HYPOTHESES & OBJECTIVES

The following hypothesis will be investigated: