NR and HIIT are both billed as ways to keep muscle young, but a new Aging Cell paper found they can pull epigenetic clocks in opposite directions. Five months of nicotinamide riboside was associated with reduced muscle epigenetic age acceleration, especially on the PCHannum, MEAT, and DunedinPACE clocks. HIIT moved some clocks the other way, raising the pace of aging on DunedinPACE. The link between the two may be mitochondria, since changes in muscle mitochondrial content correlated with changes in MEAT-based age acceleration. Here is what the study actually shows, what it doesn't, and how to read it without overreacting.
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