The Summary
Researchers evaluated the effects of five months of nicotinamide riboside (NR) supplementation and four to six weeks of high-intensity interval training (HIIT) on epigenetic age acceleration in human skeletal muscle across three independent studies. Using seven different epigenetic clocks, they discovered that NR supplementation significantly reduced muscle epigenetic age. Surprisingly, HIIT had the opposite effect, actually increasing the pace of aging according to certain clocks. Changes in muscle mitochondrial content were closely linked to these epigenetic shifts, demonstrating a novel connection between mitochondrial abundance and cellular aging markers.
Why this is interesting
For years, exercise was seen as the ultimate anti-aging tool, while supplements were viewed with skepticism. This study flips the script by showing that NR, an NAD+ precursor, successfully reversed muscle epigenetic aging, whereas short-term HIIT unexpectedly accelerated it on some metrics. This does not mean HIIT is bad—short-term intense stress can temporarily spike aging markers as muscle adapts—but it suggests NR is a powerful, direct tool for cellular rejuvenation. For readers, it highlights that combining metabolic supplements with exercise might require strategic timing to optimize muscle longevity.