Physical activity performed in the evening increases the overnight muscle protein synthetic response to presleep protein ingestion in older men

Background: The age-related decline in skeletal muscle mass is partly attributed to anabolic resistance to food intake. Dietary protein ingestion before sleep could be used as a nutritional strategy to compensate for anabolic resistance. Objective: The present study assessed whether physical activity performed in the evening can augment the overnight muscle protein synthetic response to presleep protein ingestion in older men. Methods: In a parallel group design, 23 healthy older men ( mean ± SEM age: 71 ± 1 y ) were randomly assigned to ingest 40 g protein intrinsically labeled with L-[1-13C]-phenylalanine and L-[1-13C]-leucine before going to sleep with ( PRO+EX ) or without ( PRO ) performing physical activity earlier in the evening. Overnight protein digestion and absorption kinetics and myofibrillar protein synthesis rates were assessed by combining primed, continuous infusions of L-[ring-2H5]-phenylalanine, L-[1-13C]-leucine, and L-[ring-2H2]-tyrosine with the ingestion of intrinsically labeled casein protein. Muscle and blood samples were collected throughout overnight sleep. Results: Protein ingested before sleep was normally digested and absorbed, with 54% ± 2% of the protein-derived amino acids appearing in the circulation throughout overnight sleep. Overnight myofibrillar protein synthesis rates were 31% ( 0.058% ± 0.002%/h compared with 0.044% ± 0.003%/h; P < 0.01; based on L-[ring-2H5]-phenylalanine ) and 27% ( 0.074% ± 0.004%/h compared with 0.058% ± 0.003%/h; P < 0.01; based on L-[1-13C]-leucine ) higher in the PRO+EX than in the PRO treatment. More dietary protein-derived amino acids were incorporated into de novo myofibrillar protein during overnight sleep in PRO+EX than in PRO treatment ( 0.042 ± 0.002 compared with 0.033 ± 0.002 mole percent excess; P < 0.05 ). Conclusions: Physical activity performed in the evening augments the overnight muscle protein synthetic response to presleep protein ingestion and allows more of the ingested protein-derived amino acids to be used for de novo muscle protein synthesis during overnight sleep in older men