Peter Attia, M.D.@peterattiamdInstagram

A recent paper explores the limits between muscle fiber size and aerobic capacity. What does it mean for

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what it claims

There is a potential trade-off between developing muscle mass (strength) and improving aerobic capacity.

holds up

This subject addresses what science calls the interference effect or 'concurrent training.' Historically, observational studies and meta-analyses (such as those by Wilson et al.)…

noli's read

This subject addresses what science calls the interference effect or 'concurrent training.' Historically, observational studies and meta-analyses (such as those by Wilson et al.) suggest that intense simultaneous training may slightly attenuate strength or hypertrophy gains compared to focused training, due to opposing cellular signaling pathways (mTOR for muscle, AMPK for endurance). However, for the majority of non-elite athletes, this interference is often exaggerated or negligible if nutrition and recovery are adequate. Modern research shows that it is entirely possible to improve both qualities simultaneously, especially by spacing out sessions or adjusting volume. The point raised by Peter Attia is therefore a real physiological nuance, but it should not be interpreted as an impossibility of being both strong and endurant.

the sources

Claimed by Peter Attia, M.D. Noli grades the claim, never the person.

Decoded by Noli · July 18, 2026 · the original post

What the graded evidence says

Evidence: B

Linked to, not proven to cause.

Effect: all-cause mortality by combination of aerobic + muscle-strengthening activity — 1 h/week aerobic HR 0.85 and levelling to ~0.73 at 3 h/week; adding muscle-strengthening 1-2x/week conferred further risk reduction; lowest mortality in those meeting both guidelines
Measured on: US adults (416,420 and 500,705 in two national cohorts)

These are associations from observational cohorts, not proof of cause; healthier or more motivated people may do more of both. The specific percentages sometimes quoted for one activity vs another come from particular studies and shouldn't be treated as fixed.

Peter Attia, M.D. in the Register72 claims graded · solidity 93/100See their record →