Whether you lift light weights with lots of reps or heavy weights with few reps—so long as you push until you can’t do another rep—you’ll build muscle about the same amount.
Scientific Claim
When resistance training is performed to volitional failure, muscle hypertrophy gains are similar across low-load (>15 RM), moderate-load (9–15 RM), and high-load (≤8 RM) protocols in healthy young adults, suggesting that training volume and effort, rather than load intensity, are the primary drivers of muscle growth.
Original Statement
“Although no differences in muscle hypertrophy between RT loads were found in overall (P = 0.113–0.469) or subgroup analysis (P = 0.871–0.995)... muscle hypertrophy improvements seem to be load independent.”
Evidence Quality Assessment
Claim Status
overstated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
Although the study design (systematic review of RCTs) can support causal claims, the high risk of bias in randomization and blinding across most included studies limits confidence. The claim must be probabilistic.
More Accurate Statement
“When resistance training is performed to volitional failure, muscle hypertrophy gains are likely to be similar across low-load (>15 RM), moderate-load (9–15 RM), and high-load (≤8 RM) protocols in healthy young adults, suggesting that training volume and effort, rather than load intensity, are the primary drivers of muscle growth.”
Evidence from Studies
Supporting (1)
Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis
When people lift weights until they can’t do another rep, whether they use light, medium, or heavy weights, their muscles grow about the same — what matters most is pushing hard, not how heavy the weights are.