Three Drivers Of Growth

Muscle growth needs three forces pushing in the same direction:

• Mechanical tension — the force a muscle produces against resistance. Heavier loads create more of it.
• Metabolic stress — the burning "pump" as byproducts build up during a set. Higher reps create more of it.
• Muscle damage — the tiny tears that start the repair response. Unfamiliar movements create the most.

All three matter, but mechanical tension does the heavy lifting. Chase the burn and the soreness all you want — without rising tension, the fiber has little reason to grow.