When the number of weekly resistance training sets for a muscle group is increased from 8 to 12, muscle size increases by about 0.9% compared to the lower volume.
Mechanism
Synthesis from 3 studies
Doing more sets can make muscles slightly bigger by increasing the production of non-muscle proteins inside muscle cells, as shown in 10.3389/fphys.2022.857555, but if you're already well-trained, your muscles may stop responding to extra volume, as suggested by 10.1152/japplphysiol.00476.2024 and...
Most probable mechanism
When someone does more sets of exercise per week, the repeated muscle contractions cause more calcium to flow inside muscle cells, which turns on signaling pathways that tell the cell to make more non-muscle proteins like enzymes and fluid components, leading to a small increase in muscle size — this is supported by findings in 10.3389/fphys.2022.857555, though other studies like 10.1152/japplphysiol.00476.2024 and 10.1519/SSC.0000000000000798 suggest this effect may be limited or absent in highly trained individuals.
Increased training volume leads to more frequent muscle contractions, elevating intracellular calcium flux in muscle fibers
Elevated intracellular calcium transiently activates MAPK signaling pathways, such as ERK1/2
Activated MAPK signaling increases the synthesis of non-myofibrillar proteins, including metabolic enzymes and sarcoplasmic components
Accumulation of non-myofibrillar proteins contributes to modest increases in muscle cross-sectional area without proportional myofibrillar growth
Less supported by current evidence, but not ruled out
In individuals already accustomed to high training volumes, additional sets may not trigger further muscle growth because cellular signaling and protein synthesis pathways become less responsive — this is suggested by findings in 10.1152/japplphysiol.00476.2024 and 10.1519/SSC.0000000000000798, which show minimal or no additional growth despite volume increases.
Chronic exposure to high training volume reduces sensitivity of anabolic signaling pathways to further mechanical or metabolic stimuli
Reduced signaling sensitivity limits the upregulation of protein synthesis machinery, preventing additional muscle growth despite increased volume
Evidence from Studies
Supporting (1)
Community contributions welcome
Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations
Contradicting (2)
Community contributions welcome
Training Volume Increases Or Maintenance Based On Previous Volume: The Effects On Muscular Adaptations In Trained Males.
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.