1. What’s the switch (mTOR)?
Hard training (push-ups, bench, squat…) turns on mTOR (really mTORC1) inside muscle cells — like a “muscle factory switch.”
When it’s on, muscle protein synthesis (MPS) rises for a bit — roughly a day or two of “sticky” growth mode. The name is fancy; the job is simple: don’t disappear for weeks — flip it on often.
2. Why hard sets flip the switch
The strongest hypertrophy signal is mechanical tension — muscle working under load while lengthening or shortening. Reviews often rank tension #1.
Mechanical stimulus → cellular signals rise → mTOR helps bump protein synthesis briefly. Pathways are complex; in practice, stack quality hard sets often.
3. Why flipping it often can help
The switch doesn’t stay on forever. Rare sessions mean long “off” stretches. Rest the same area a day or two, then train again — more days with the switch on.
Frequency meta-analyses often favor ≥2×/week per muscle (when volume is matched) over once weekly. You don’t need to smash the same area daily — “often enough” beats “once in a while, all-out.”
4. Sets and failure
Stopping 1–2 reps short of failure is fine. You don’t have to take every set to failure. Proximity-to-failure metas don’t strongly support “must fail.”
Don’t count easy warm-ups — count real working sets. Think “~N weekly sets for this lift,” and spread them across the week to flip the switch more often.
5. Evidence (papers)
Links go to DOI / PubMed / PMC. Titles, years, authors only. Interpretations are simplified.
- Schoenfeld BJ (2010). The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res.
- You JS, Lincoln HC, Kim CR, Frey JW, Goodman CA, Zhong XP, Hornberger TA (2014). DGKζ and phosphatidic acid in mechanical activation of mTOR. J Biol Chem.
- Goodman CA (2019). Role of mTORC1 in mechanically induced increases in translation and skeletal muscle mass. J Appl Physiol.
- Bodine SC (2022). The role of mTORC1 in the regulation of skeletal muscle mass. Faculty Reviews.
- Wackerhage H, Schoenfeld BJ, et al. (2019). Stimuli and sensors that initiate skeletal muscle hypertrophy following resistance exercise. J Appl Physiol.
- Schoenfeld BJ, Ogborn D, Krieger JW (2016). Effects of resistance training frequency on measures of muscle hypertrophy: a systematic review and meta-analysis. Sports Med.
- Refalo MC, Helms ER, Trexler ET, Hamilton DL, Fyfe JJ (2023). Influence of resistance training proximity-to-failure on skeletal muscle hypertrophy: a systematic review with meta-analysis. Sports Med.
- Van Every DW, Lees MJ, Wilson B, Nippard J, Phillips SM (2025). Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions. J Sport Health Sci.