When you exercise a muscle, you tear the muscle fibers, which build back stronger to increase muscle mass.
"When you exercise a muscle, you tear the muscle fibers, they build back stronger, and that's how you gain muscle mass." (said at 1:04:00)
The classic idea that resistance training causes muscle growth by creating microscopic tears in muscle fibers that 'build back stronger' is contradicted by modern exercise physiology. Research demonstrates that exercise-induced muscle damage is not the primary driver or prerequisite for muscle hypertrophy. Instead, mechanical tension stimulates intracellular signaling pathways that elevate muscle protein synthesis (MPS) above muscle protein breakdown. When muscle damage is high, early elevations in protein synthesis are directed toward repairing and remodeling damaged tissue rather than accumulating new contractile protein. Substantial hypertrophy occurs when muscle damage is minimal or attenuated, and training regimens designed to minimize microtrauma induce comparable hypertrophy to damage-inducing protocols.
- contradicts: Resistance training-induced changes in integrated myofibrillar protein synthesis are relat… (The Journal of physiology 2016)
"Initial MyoPS response post-RE in an RT programme is not directed to support muscle hypertrophy, coinciding with the greatest muscle damage. However, integrated MyoPS is quickly 'refined' by 3 weeks of RT, and is related to muscle hypertrophy. We conclude that muscle hypertrophy is the result of accumulated intermittent changes in MyoPS post-RE in RT, which coincides with progressive attenuation of muscle damage." (abstract, conclusions, passage verified)
pubmedfull study (doi) - contradicts: The development of skeletal muscle hypertrophy through resistance training: the role of mu… (European journal of applied physiology 2018)
"Furthermore, RT protocols that do not promote significant muscle damage still induce similar muscle hypertrophy and strength gains compared to conditions that do promote initial muscle damage. Thus, we conclude that muscle damage is not the process that mediates or potentiates RT-induced muscle hypertrophy." (abstract, conclusions, passage verified)
pubmedfull study (doi)