Hormonal
In healthy young humans, changes in skeletal muscle mass in response to resistance exercise, disuse, and aging are primarily driven by alterations in muscle protein synthesis (MPS), while muscle protein breakdown (MPB) remains largely unchanged or plays a negligible role.
To maintain or build muscle, prioritize resistance exercise and protein intake to stimulate muscle protein synthesis. You do not need to worry about 'blocking' muscle breakdown as a primary strategy, as your body naturally regulates this, and forcing suppression may be counterproductive. Consistent loading is the key lever.
ample evidence shows that changes in muscle protein synthesis (mixed and myofibrillar) are primarily responsible for changes in muscle mass in response to resistance exercise... ageing... and disuse... in humans
Why this rating
Based on a review of multiple human studies using stable isotope tracers (D2O and infusions), though it is a review rather than a primary trial.
Source
Turning over new ideas in human skeletal muscle proteostasis: What do we know and where to from here?
Changhyun Lim et al. · Experimental Physiology · 2025
DOI 10.1113/ep092353
More from this paper
- Deuterated water (D2O) ingestion is a valid and increasingly used method for measuring long-term muscle protein synthesis in humans, providing insights that complement acute tracer infusion methods.Good
- In aging skeletal muscle, the progressive loss of mass (sarcopenia) is largely driven by anabolic resistance—a desensitized muscle protein synthesis response to stimuli like loading and protein ingestion—rather than increased protein breakdown.Good
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