Back to parkrun on a busy schedule: how NMN supports your energy as you train
Saturday mornings at parkrun have become something of a national ritual. Across more than 1,200 UK events, hundreds of thousands of us pull on trainers and tackle a 5km — many of us doing so while juggling demanding jobs, young families, and a calendar that never quite settles down.
If that sounds like you — and you've noticed that your energy isn't quite what it used to be — you're not imagining it. In my GP practice I see a steady stream of patients who want to get fitter, who've signed up for parkrun or rejoined the gym, and who feel they're running on empty before they've even laced up.
Here's what's happening, and where NMN fits in.
Why busy lives leave us low on energy
Energy isn't just about how many hours you slept last night. At a cellular level, it's produced by your mitochondria — tiny structures inside almost every cell that convert what you eat and breathe into usable fuel.
Mitochondria depend on a coenzyme called NAD+ (nicotinamide adenine dinucleotide) to do that work. NAD+ is involved in hundreds of enzymatic reactions across the body, including those that govern energy production, DNA repair, and the regulation of your body clock.
The problem is that NAD+ levels decline naturally with age — published research suggests measurably so from your thirties onwards. Add in the modern stressors most of my patients describe (interrupted sleep, long working days, irregular meals, alcohol), and the demand on your NAD+ pool grows just as the supply is dwindling.
That's the biological backdrop to feeling persistently tired even when, on paper, you should have plenty of energy to draw on.
Where NMN comes in
NMN — nicotinamide mononucleotide — is a direct precursor to NAD+. Put simply, your body uses NMN to make NAD+. Supplementing with NMN is one of the most studied ways to support healthy NAD+ levels as you age.
The published evidence is encouraging. Clinical trials have shown that oral NMN supplementation can raise blood NAD+ levels in healthy adults, and several studies have linked NMN to improvements in measures of physical function, walking endurance, and aerobic capacity in middle-aged and older participants. The research is still developing, but the direction of travel is consistent.
For someone returning to parkrun on a busy schedule, the relevance is straightforward. Aerobic exercise places real demand on your mitochondria. Supporting the cellular machinery that produces your energy gives your training a better foundation to build on.
What I tell my patients about getting started
If you're considering NMN as part of your return to running or general fitness, a few practical points from clinical experience:
Take it consistently, in the morning. NAD+ follows a circadian rhythm, peaking in the morning hours, and most participants in the published trials take their NMN on waking. That also fits neatly with parkrun mornings.
Pair it with the basics. NMN is not a substitute for sleep, hydration, protein, or progressive training. It supports a body that's already being looked after — it doesn't compensate for one that isn't. The patients who do best with any supplement are the ones who've also addressed their sleep window, their morning protein intake, and their walking volume during the working week.
Be patient with what you notice. The cellular changes happen quickly, but the felt experience — steadier energy through the afternoon, fewer crashes after a hard session, easier early starts — tends to build over four to eight weeks.
Speak to your GP if you take prescription medication or have a chronic condition. NMN has a strong safety profile in the published literature, but personalised advice always sits above general guidance.
Choosing a quality NMN
Supplement quality varies enormously. Three things I'd look for:
Purity. Independent testing matters. The NMN you take should be backed by certificates of analysis, not just claims on a label.
Dose. Most clinical studies use 250mg to 500mg per day. Significantly under-dosed products are common and simply won't reproduce what the research is reporting.
Form. NMN can be paired with complementary compounds — resveratrol is a common partner, supporting the sirtuin pathways that NAD+ activates. For some patients I'd suggest the simpler single-ingredient option; for others, a combined formulation makes more sense.
At Little Ox we've designed both options around exactly these considerations. Our NMN Pure is for those who want a clean, single-ingredient product. NMN Plus combines NMN with resveratrol for a more comprehensive approach to cellular metabolism support.
The bigger picture
parkrun is a wonderful example of what works in modern public health: free, social, repeatable, and built around showing up rather than performing. If you're using it as the anchor for getting back to fitness on a busy life, give yourself the cellular support to match. Sleep first, food next, training third — and a well-chosen supplement can earn its place alongside those fundamentals.
I'll see you at the start line.
Dr Chun Tang is a practising NHS GP and co-founder of Little Ox. The information in this article is general health information and is not a substitute for personalised medical advice. If you have a medical condition or take prescription medication, please speak to your GP before starting any new supplement.