Lifting weights for three months didn’t increase the number of muscle fibers in young guys’ biceps, so their muscles got bigger without adding new fibers.

31

Pro

0

Against

Evidence from Studies

Supporting (1)

31

Community contributions welcome

31

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.

Cross-Sectional Study

Human

1996 Nov

The study looked at whether lifting weights for 12 weeks changed the number of muscle fibers in young men's arms, and found no real change — just like the claim says.

Contradicting (0)

0

Community contributions welcome

No contradicting evidence found

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.

Source Study

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.

Score: 31

DOI: 10.1152/JAPPL.1996.81.5.2004

Similar Assertions

Lifting weights for up to 6 months probably doesn’t increase the number of muscle fibers in your arms or legs — instead, your muscles grow because the existing fibers get bigger, not because you grow new ones.

39

0

90%

When people lift weights, their arm and leg muscles show similar changes in muscle fiber numbers — and in both, we don’t see clear signs of new muscle fibers forming.

39

0

88%

Lifting weights for three months makes the muscle fibers in young men's biceps get bigger — both the endurance-type and power-type fibers.

31

0

88%

Whether you're new to lifting weights or already experienced, your muscles seem to add new fibers at about the same rate when you start resistance training — at least in the first 6 months.

39

0

83%

How long you lift weights—up to 6 months—doesn’t seem to change the number of muscle fibers you have, according to this claim.

39

0

80%