When lifting weights until complete fatigue, using momentum from body movement does not lessen muscle growth in the targeted muscles.
Mechanism
Synthesis from 1 study
When you push your muscles until they can't move anymore, the force they feel is what makes them grow — not whether you swing the weight or lift it slowly. As long as you reach that point of total effort, your muscles get the signal to build more tissue.
Most probable mechanism
When you push a muscle until it can't move anymore, the fibers are stretched and squeezed hard enough to trigger growth signals, no matter if you swing the weight or lift it slowly — the key is reaching that point of total effort.
Muscle fibers are subjected to high mechanical tension during the final repetitions of a set performed to muscular failure, regardless of external momentum.
High mechanical tension activates intracellular signaling pathways, including mTOR and MAPK, which initiate protein synthesis and suppress protein breakdown.
Satellite cells are recruited and fuse with existing muscle fibers, contributing nuclei that support increased myofibrillar protein deposition.
The cumulative metabolic stress and cellular damage from failure-level effort sustain an anabolic environment long enough to drive net muscle protein accretion.
Evidence from Studies
Supporting (1)
Community contributions welcome
Do Cheaters Prosper? Effect of Externally Supplied Momentum During Resistance Training on Measures of Upper Body Muscle Hypertrophy
Contradicting (0)
Community contributions welcome
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.