Does the muscle protein synthetic response to exercise and amino acid-based nutrition diminish with advancing age? A systematic review.
Level 1 - systematic review of randomized trials
Systematic review of experimental studies examining human muscle protein synthetic responses.
PubMed 27555299 · doi:10.1152/ajpendo.00213.2016
What was done
A systematic review was conducted to evaluate whether acute muscle protein synthesis (MPS) responses to exercise (endurance or resistance), amino acid-based nutrition, or their combination are impaired in older compared to younger adults. Study arms were classified as providing sufficient or insufficient evidence of age-related anabolic resistance across three intervention models: exercise alone, amino acid-based nutrition alone, or combined exercise and nutrition.
What was found
Across the identified literature: - Exercise alone: 8 of 17 study arms showed sufficient evidence of age-related muscle anabolic resistance. - Amino acid-based nutrition alone: 8 of 21 study arms showed sufficient evidence of anabolic resistance. - Combined exercise and nutrition: 2 of 10 study arms showed sufficient evidence of anabolic resistance.
Why it matters
These findings indicate that age-related anabolic resistance is not an insurmountable defect, as combining adequate exercise with sufficient protein/amino acid and leucine intake can restore muscle protein synthesis rates in older adults to levels comparable to younger adults.
Limits
The review assesses acute surrogate synthetic rates rather than chronic hypertrophy or functional strength. Synthesis was based on categorical classification of study arms rather than quantitative meta-analysis, and total participant count, specific age thresholds, and study quality ratings were not provided in the abstract.
Cited by
- context Postmenopausal women require at least double the premenopausal amount of dietary leucine to trigger muscle protein synthesis.