When you lift weights, doing a few heavy reps makes you stronger, doing lots of light reps helps your stamina, and doing a medium amount builds bigger muscles.
Evidence from Studies
Supporting (1)
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Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones
The study tested different rep ranges in weightlifting and found that low reps build strength best, high reps boost endurance, and middle reps grow muscle size, just like the claim says.
Contradicting (4)
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The impact of repetition mechanics on the adaptations resulting from strength-, hypertrophy- and cluster-type resistance training
The study looked at lifting weights with different rep counts but didn't test the high reps (20-28) for endurance like the claim says, and it found that lower reps were better for strength than the hypertrophy rep range, which partly goes against the claim.
Muscle hypertrophy and strength gains after resistance training with different volume matched loads: a systematic review and meta-analysis.
The study shows that lifting heavy weights makes you stronger, but muscle growth is similar no matter how heavy you lift if the total work is the same. It doesn't test endurance at all, so the claim is only partly right and goes too far.
Divergent Strength Gains but Similar Hypertrophy After Low-Load and High-Load Resistance Exercise Training in Trained Individuals: Many Roads Lead to Rome.
The study found that both low reps and high reps built similar muscle size and strength in trained people, which goes against the idea that different rep ranges do different things.
The study says that doing different numbers of reps in weight training doesn't always lead to just one specific result like more strength or endurance, which goes against the claim that each rep range has a special benefit.
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.