If you train hard enough to fail on every set, how heavy the weights are matters less than your body’s natural ability to grow muscle.

Scientific Claim

When resistance training is performed to volitional fatigue, muscle hypertrophy is primarily mediated by inherent biological factors rather than external training variables like load.

Original Statement

“We conclude that when effort is matched (i.e. working to volitional muscular fatigue), RET-induced hypertrophy is mediated to a far greater degree by inherent endogenous biological factors, which account for a large proportion of the heterogeneity between individuals.”

From study:Resistance training load does not determine resistance training-induced hypertrophy across upper and lower limbs in healthy young males.

Evidence Quality Assessment

Claim Status

overstated

Study Design Support

Design supports claim

Appropriate Language Strength

association

Can only show association/correlation

Assessment Explanation

While randomization supports causal inference, the claim 'mediated to a far greater degree' implies a strong causal hierarchy not fully verifiable without full methods or control of confounders. 'Associated with' is more conservative.

More Accurate Statement

“When resistance training is performed to volitional fatigue, muscle hypertrophy is associated with a greater influence from inherent biological factors than from external training variables like load.”

Evidence from Studies

Supporting (1)

Resistance training load does not determine resistance training-induced hypertrophy across upper and lower limbs in healthy young males.

Randomized Controlled Trial

Human

2025 Dec 31

When people lift weights until they can’t do another rep, whether they use heavy or light weights, their muscles grow about the same — and how much they grow depends more on their body’s natural biology than on how heavy the weights are.

Contradicting (0)

No contradicting evidence found

Source Study

Resistance training load does not determine resistance training-induced hypertrophy across upper and lower limbs in healthy young males.

Score: 46

DOI: 10.1113/JP289684

Similar Assertions

When you train hard enough to fail on every set, how heavy the weights are matters less than your body’s natural ability to grow muscle.

100%

When people lift weights until they can't do another rep, their muscles grow about the same amount whether they use heavy or light weights — and how much they grow depends more on their own body than on how heavy the weights are.

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Whether you lift heavy weights for fewer reps or light weights for more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.

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Whether you lift heavy weights with fewer reps or light weights with more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.

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People grow muscle at very different rates — but each person tends to grow their arms and legs similarly, no matter what weight they use. This means your genes and biology matter more than how heavy your weights are.

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