Low-load resistance training during step-reduction attenuates declines in muscle mass and strength and enhances anabolic sensitivity in older men
Bibliographic record
Abstract
Step-reduction (SR) in older adults results in muscle atrophy and an attenuated rise in postprandial muscle protein synthesis (MPS): anabolic resistance. Knowing that resistance exercise (RT) can enhance MPS, we examined whether RT could enhance MPS following 2 weeks of SR. In addition, as we postulated that SR may impair feeding-induced vasodilation limiting nutrient delivery to muscle, we also examined whether citrulline (CIT), as an arginine and nitric oxide precursor, could attenuate muscle anabolic resistance accompanying SR. We used a unilateral leg model to compare older subjects' who had undergone SR to a loaded condition of SR plus RT (SR + RT). Thirty older men (70 ± 1 years) underwent 14 days of SR (<1500 steps/day) with supplementation of either 5 g/day CIT or glycine placebo. Throughout SR, subjects performed unilateral low-load RT thrice weekly. We assessed muscle protein synthesis in the postabsorptive and postprandial state (20 g whey isolate plus 15 g glycine or as micellar-whey with 5 g CIT or 15 g glycine, n = 10/group). As MPS was similar after ingestion of either whey isolate, micellar-whey, or micellar-whey + CIT data related to different dietary groups were collapsed to compare SR and SR + RT legs. Subjects' daily steps were reduced by 80 ± 2% during SR (P < 0.001) compared with baseline. Leg fat-free mass decreased with SR (-124 ± 61 g) and increased in the SR + RT (+126 ± 68 g; P = 0.003). Myofibrillar FSR was lower (P < 0.0001) in the SR as compared with the SR + RT leg in the postabsorptive (0.026 ± 0.001%/h vs. 0.045 ± 0.001%/h) and postprandial states (0.055 ± 0.002%/h vs. 0.115 ± 0.003%/h). We conclude that low-load RT, but not supplementation with CIT, can attenuate the deleterious effects of SR in aging muscle.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".