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causal
Analysis v1
Supported

Lifting weights until you can't lift anymore makes muscles grow bigger no matter how heavy the weights are, but using heavier weights builds more strength than lighter ones.

48
Pro
41
Against

Evidence from Studies

Supporting (3)

48

Community contributions welcome

48

Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis

Systematic Review With Meta-Analysis
Human
2021 Jun 1

The study found that lifting weights until you can't anymore makes muscles grow the same no matter how heavy the weights are, but using heavier weights makes you stronger faster than using lighter ones, which matches the claim exactly.

48

Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis

Systematic Review With Meta-Analysis
Human
2021 Jun 1

The study found that lifting weights until you can't anymore makes muscles grow the same no matter how heavy the weights are, but using heavier or medium weights makes you stronger faster than using lighter weights, which matches the claim.

28

Muscle hypertrophy and strength gains after resistance training with different volume matched loads: a systematic review and meta-analysis.

Systematic Review With Meta-Analysis
Human
2022 Apr

The study looked at lifting weights with different amounts of weight but the same total work, and found that bigger muscles happen no matter the weight, but lifting heavier weights makes you stronger than lifting lighter ones, which matches the claim.

Contradicting (2)

41

Community contributions welcome

41

Low-Load Resistance Training Performed to Muscle Failure or Near Muscle Failure Does Not Promote Additional Gains on Muscle Strength, Hypertrophy, and Functional Performance of Older Adults

Randomized Controlled Trial
Human
2022 May 1

The study only looked at low-weight training in older adults and didn't compare it to heavier weights, so it can't tell us if heavy weights are better for strength or if training to failure makes muscles grow regardless of weight, which is what the claim says.

41

Low-Load Resistance Training to Volitional Failure Induces Muscle Hypertrophy Similar to Volume-Matched, Velocity Fatigue

Randomized Controlled Trial
Human
2022 Jun 1

The study looked at lifting light weights until you can't anymore and lifting heavy weights, but it didn't test medium weights. It partly agrees with the claim but doesn't check everything mentioned.

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.

Similar Assertions

When people who are already fit push themselves as hard as they can during weight training, it doesn't matter if they lift heavy weights for a few reps or lighter weights for many reps—both ways build muscle about the same.

53
0
93%

If you lift weights until you can’t do another rep, your muscles will grow about the same no matter how heavy the weights are—but you’ll get stronger faster if you lift heavier weights.

53
0
92%

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.

48
0
90%

If you lift weights until you can’t do another rep, it doesn’t matter if you’re using light, medium, or heavy weights—you’ll still grow your muscles about the same, as long as you push yourself hard and do enough total work.

48
0
90%

Lifting light weights until you can't do another rep builds muscle just as well as lifting light weights until your speed slows down a lot, as long as you do the same total amount of work.

41
0
89%

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