NMN for Athletes: Does It Improve Endurance and VO₂ Max?

Nicotinamide mononucleotide (NMN) is marketed to athletes as an endurance booster — a supplement that raises NAD+, fuels the mitochondria that power aerobic work, and lifts your aerobic ceiling. Unlike most NMN performance claims, this one isn't pure hand-waving: there is a real, randomized, placebo-controlled human trial behind it. But it's one trial, in a specific population, with important limits — and the rest of the NMN-and-exercise literature is more sobering than the marketing lets on. This page is built around that single study, because being honest about athletic NMN means being precise about exactly what has and hasn't been shown.

The mechanism: why NMN *should* help endurance

The rationale is legitimate. NAD+ is the central electron carrier in the reactions that turn food into ATP, and it powers the mitochondria that endurance performance depends on. NMN is an oral NAD+ precursor that reliably raises blood NAD+ in a dose-dependent way in humans ¹, and a pharmaceutical-grade NMN cleanly increased circulating NAD+ and its metabolome ². NAD+ also tends to fall with age and metabolic stress, and it sits upstream of the sirtuin and PGC-1α signaling that drives mitochondrial biogenesis — exactly the adaptations endurance training is trying to provoke. So on paper, "raise NAD+ → better aerobic metabolism → more endurance" is a coherent hypothesis ⁶.

The catch — and it's the same catch that haunts the entire NAD+ field — is that raising the NAD+ biomarker has repeatedly failed to translate into improved muscle function. The clearest example: when nicotinamide riboside (NR, NMN's sister precursor) augmented the aged human muscle NAD+ metabolome, it did not improve bioenergetics or physical performance ⁵. The fuel gauge moved; the engine output didn't. That's the backdrop against which the one positive NMN trial has to be read.

The one real study: 48 amateur runners

The headline evidence is a 2021 randomized, double-blind trial published in the Journal of the International Society of Sports Nutrition. Researchers gave 48 recreationally trained amateur runners NMN or placebo for six weeks across several daily doses — a low dose, a middle dose, and a high dose, roughly spanning 300 to 1,200 mg/day — while all groups followed the same exercise training ³.

The result that made headlines: the NMN groups showed greater improvement in aerobic capacity during exercise than placebo, and the effect was dose-dependent — the middle and higher doses (around 600 and 1,200 mg/day) drove the benefit, while the lowest dose did not clearly separate from placebo ³. The authors attributed the gain to enhanced oxygen utilization by skeletal muscle rather than to changes in the heart or lungs.

That's a genuine, peer-reviewed, placebo-controlled positive result — which is more than most performance supplements can claim. It's the reason "NMN for endurance" isn't simply a myth. But the same study is also the reason you should keep your expectations measured.

Why one study can't carry the claim

Read carefully, the runners trial supports a narrow statement — NMN may modestly improve a measure of aerobic capacity in amateur runners over six weeks — not the broad "NMN boosts your VO₂ max" sold on supplement labels. Several limits matter:

• •It's a single study. No independent group has replicated it. In nutrition science, unreplicated single trials frequently shrink or vanish on repetition, and a lone positive result is a starting point, not a settled fact.
• •The population was specific. These were amateur, recreationally trained runners — not elite athletes, and not sedentary beginners. Whether the effect generalizes up to trained competitors or out to the general gym-goer is untested.
• •"Aerobic capacity" measures aren't a clean VO₂ max win. The trial reported improvements in aerobic-capacity indices derived during exercise testing; this is suggestive of better oxygen utilization, but it is not the same as a large, decisive jump in maximal oxygen uptake, and it wasn't paired with race-time or competitive-outcome data.
• •Six weeks is short. Endurance adaptations and any supplement's real-world value play out over months and seasons, not six weeks.

What the rest of the NMN/NAD+ exercise literature shows

Step beyond the runners study and the picture cools considerably. A 2025 systematic review and meta-analysis of NMN and NR specifically on skeletal muscle mass and function found that, pooled across trials, these precursors did not produce reliable improvements in muscle strength or mass — reinforcing that raising NAD+ is not a dependable route to better muscle output ⁴. A separate placebo-controlled trial of NMN in older adults with diabetes and impaired physical performance reported only limited functional effects ⁷. And the broader review of NAD+ therapeutics and exercise adaptation concludes the human performance data are early and inconsistent, with mechanism running well ahead of proven benefit ⁶.

So the honest synthesis is a split-screen: one positive aerobic-capacity trial in runners on one side, and a meta-analysis plus a null NR muscle study plus a cautious review on the other. That's not "NMN doesn't work" — it's "the strongest claim the evidence currently supports is a single, unreplicated, modest, population-specific endurance signal."

Practical reality for athletes

If you're an athlete weighing NMN, a few honest takeaways:

• •The endurance evidence is one study, so treat any purchase as an experiment with uncertain odds, not a proven edge. For dosing context, the trial used roughly 600–1,200 mg/day; our NAD+ dosage guide walks through how those numbers map to common products.
• •NMN is not a stimulant and won't give you an acute pre-workout lift — any plausible benefit is a slow, adaptation-level effect, which is exactly why people overestimate it. We unpack the recurring "does NAD+ boost energy" question and its trial-by-trial reality in does NAD+ actually boost energy.
• •The fundamentals still dominate. Structured training, adequate protein, sleep, and iron status move endurance far more reliably than any NAD+ precursor, and none of the NMN data displaces that.
• •If you do try it, product quality matters more than the thin efficacy gap between brands — see how the options compare on third-party purity and dose transparency in the best NMN supplements, rated by evidence.

Bottom line

NMN for endurance is the rare NAD+ athletic claim with an actual randomized trial behind it: 48 amateur runners, six weeks, a dose-dependent improvement in aerobic capacity at roughly 600–1,200 mg/day ³. That's real and worth knowing. But it's a single, unreplicated study in a specific population, and the surrounding literature — a meta-analysis finding no reliable muscle benefit ⁴, a null NR performance result ⁵, and a cautious exercise-adaptation review ⁶ — keeps the verdict modest. Promising, not proven. For the full evidence picture on what raising NAD+ can and can't do, start with our NAD+ therapy evidence pillar, and see where the products land on our NAD+ rankings hub.