# NR May Slow Muscle Aging Clocks While Hard Interval Training Speeds Some Up

*The Divergent Effects of Nicotinamide Riboside and High-Intensity Exercise Training on Skeletal Muscle Epigenetic Aging.*

- **Evidence Level**: Preliminary
- **Publication Types**: Journal Article
- **Journal**: Aging cell
- **Sample Size**: Adults across three independent human muscle studies
- **Authors**: Heikkinen A, Uusitalo-Kylmälä L, Blom I, Helge JW, Gillberg L, Seaborne R, Larsen S, Jacques M, Grolaux R, Aaltonen S, Kaprio J, van der Kolk BW, Heinonen S, Eynon N, Pietiläinen KH, Kivelä R, Pirinen E, Ollikainen M
- **Published**: 2026-07-24
- **Topics**: nicotinamide riboside, NAD+, epigenetic clock
- **DOI**: https://doi.org/10.1111/acel.70638
- **Original Source**: https://pubmed.ncbi.nlm.nih.gov/42481916/

## Summary

Nicotinamide riboside, a popular NAD+ booster, was linked to slower epigenetic aging in muscle across several aging clocks. Surprisingly, high-intensity interval training pushed some of those clocks in the opposite direction, appearing to speed up the pace of aging. The two interventions worked against each other on these markers, which is unexpected and needs more study.

## Practical Takeaway

This study suggests NR and HIIT may affect muscle epigenetic aging clocks in opposite ways.

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