Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial 1 , 2 , 3

BACKGROUND: Leucine is a key amino acid involved in the regulation of skeletal muscle protein synthesis. OBJECTIVE: We assessed the effect of the supplementation of a lower-protein mixed macronutrient beverage with varying doses of leucine or a mixture of branched chain amino acids (BCAAs) on myofibrillar protein synthesis (MPS) at rest and after exercise.