Dose-Dependent Effects of Protein Ingestion and Resistance Exercise on Muscle Protein Synthesis in Aging Adults: A Literature Review
Bibliographic record
Abstract
Introduction: Sarcopenia can lead to physical disability and lower quality of life, but increasing muscle protein synthesis in older adults may reduce its effects. Dose-response curves may be used to determine the optimal protein dose in rested and exercised muscle to elicit maximal muscle protein synthesis. Methods: A literature review was conducted to explore and summarize the findings on the following topics: the mechanisms of muscle protein synthesis, anabolic resistance, and the dose-responses of muscle protein synthesis to anabolic stimuli in both younger and older individuals. Results: Reduced phosphorylation in downstream targets of the mammalian target of rapamycin complex 1 pathway is characteristic of muscle protein synthesis in older muscle. Compared to younger muscle, older muscle can elicit a similar maximal muscle protein synthesis response, but is less sensitive to lower doses of protein ingestion. With ingestion of 40g of whey protein, the fractional synthetic rate in older muscle is similar to that of younger muscle with 20g of whey protein ingestion. Marked increases in amino acid oxidation are also observed. Discussion: Anabolic resistance can be biochemically explained by reduced phosphorylation in the mammalian target of rapamycin complex 1 pathway. Due to this phenomenon, older individuals require greater anabolic stimuli to achieve maximal muscle protein synthesis. However, the most effective protein dose for maximal muscle protein synthesis in older muscle is not well-established. Conclusion: The muscle protein synthesis dose-response curve for older individuals reveals blunted responses to stimuli due to anabolic resistance. Further research is warranted to determine the optimal protein dose for maximal muscle protein synthesis in older adults.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.003 | 0.002 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".