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# Mechanical Tension (Hypertrophy Driver)
The primary driver of muscle growth is mechanical tension accumulated over time — total volume under load — not metabolic stress (the "pump") or muscle damage (soreness), which are secondary/minor contributors despite being what most lifters chase.
Chasing soreness or the pump as a proxy for "did this work" is misleading. What predicts growth is total working sets close to failure, tracked over the week — 10–20 sets/muscle group/week, 6–30 reps, sweet spot 8–15.
(Source: Dr. Andy Galpin: Optimal Protocols to Build Strength & Grow Muscles — Huberman Lab)
Hypertrophy stimulus works through three overlapping pathways: mechanical tension, metabolic disturbance, and muscle damage. Only the combination of low frequency AND low intensity/volume reliably fails to produce growth — muscle damage itself is explicitly not required for hypertrophy ("it's a flat out lie that you have to break a muscle down to cause it to grow").
Metabolic disturbance in practice: Blood flow restriction (BFR) training — a cuff occluding blood flow while training at very light loads (20–30% of 1RM) taken to fatigue — is claimed to match heavier-load training for hypertrophy by driving the metabolic-disturbance pathway rather than mechanical tension. Useful when heavy loading isn't available or appropriate.
Mechanical tension is transduced via the mTOR/AKT pathway (activated by tension + amino-acid/protein availability) into contractile-protein (myofibrillar) hypertrophy — see Strength vs. Hypertrophy Physiology for the full mechanism, including how this differs from non-contractile sarcoplasmic hypertrophy.
Related: Hypertrophy Programming