When people who’ve never lifted weights before start training, some gain just a little muscle—like half a kilo—while others gain a lot, up to three kilos, in about two to three months.
Claim Language
Language Strength
probability
Uses probability language (may, likely, can)
The claim uses 'varies widely' and 'ranging from', which indicate a spectrum of possible outcomes rather than a guaranteed or universal result, suggesting likelihood or variability rather than certainty.
Context Details
Domain
exercise_science
Population
human
Subject
Individual responsiveness to resistance training in untrained individuals
Action
varies widely, resulting in
Target
fat-free mass gains ranging from 0.4 kg to 3 kg over 10–12 weeks
Intervention Details
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.
Evidence from Studies
Supporting (4)
Heavy resistance exercise training in older men: A responder and inter-individual variability analysis
This study found that when older men lifted weights, some gained a lot of muscle and others gained very little—even though they all did the same workout. This matches the claim that people respond very differently to weight training.
Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis
This study looked at how hard people should work out to build muscle and found that not everyone responds the same way — some gain more, some less — which matches the claim that people’s muscle gains from weight training vary a lot.
Muscular and Systemic Correlates of Resistance Training-Induced Muscle Hypertrophy
This study found that some people gained a lot of muscle from weight training, while others barely gained any—even when doing the same workout—showing that everyone responds differently, just like the claim says.
VDR Gene Polymorphisms and Inter-Individual Variability in Response to Resistance Training.
This study found that people respond differently to weight training because of their genes — some gain more muscle than others, which is exactly what the claim says.
Contradicting (1)
Pectoralis Clavicular and Sternocostal Thicknesses Increase Similarly in Response to One and Three Sets of Pec Deck Resistance Training in Untrained Young Men
This study only looked at how one exercise affected one muscle in the chest, not how much total muscle people gained overall. It doesn’t show how much variation there is between people, so it can’t prove or disprove the claim.