Physical Activity Performed in the Evening Increases the Overnight Muscle Protein Synthetic Response to Presleep Protein Ingestion in Older Men.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 27281811 · doi:10.3945/jn.116.230086
What was done
Twenty-three healthy older men (mean age 71 ± 1 y) were randomly assigned in a parallel-group design to ingest 40 g of intrinsically labeled casein protein (l-[1-13C]-phenylalanine and l-[1-13C]-leucine) before sleep either with (PRO+EX) or without (PRO) performing physical activity earlier in the evening. Continuous infusions of stable isotope tracers (l-[ring-2H5]-phenylalanine, l-[1-13C]-leucine, and l-[ring-2H2]-tyrosine) combined with overnight blood and muscle sampling were used to assess protein digestion, absorption kinetics, and myofibrillar protein synthesis rates.
What was found
Protein was normally digested and absorbed, with 54% ± 2% of protein-derived amino acids appearing in the circulation overnight. Overnight myofibrillar protein synthesis rates were significantly higher in PRO+EX than PRO alone: - By l-[ring-2H5]-phenylalanine tracer: 0.058% ± 0.002%/h vs. 0.044% ± 0.003%/h (31% higher, P < 0.01) - By l-[1-13C]-leucine tracer: 0.074% ± 0.004%/h vs. 0.058% ± 0.003%/h (27% higher, P < 0.01) More dietary protein-derived amino acids were incorporated into de novo myofibrillar protein overnight in PRO+EX than in PRO (0.042 ± 0.002 vs. 0.033 ± 0.002 mole percent excess, P < 0.05).
Why it matters
Evening physical activity before presleep protein ingestion improves overnight muscle protein synthesis and dietary amino acid incorporation, offering a strategy to help counter age-related anabolic resistance.
Limits
The sample size was small (n = 23) and included only healthy older men, limiting generalizability to women or frail elderly individuals. The study only measured acute overnight synthesis rates rather than long-term gains in muscle mass, strength, or functional performance.
Cited by
- supports Performing exercise with a specific limb directs a greater proportion of ingested dietary amino acids into that exercised muscle compared to non-exercised muscle.