NNOXX One analysed my half marathon effort – here is exactly what they found

NNOXX One analysed my half marathon(-like) effort – here is exactly what it found

NNOXX One is one of a new generation of consumer/lab-grade sports sensors that for the first time give insights into new aspects of our physiology. Heart Rate, Muscle Oxygen and Nitric Oxide are 3 key performance biomarkers for understanding our training and racing.

What’s specifically new here is that NNOXX measures nitric oxide in real-time alongside muscle oxygen.  The latter (SmO2) is unusual but not novel and is also measured by sensors such as Moxy and Train.Red.

More: nnoxx.com

Nitric Oxide (NO), Oxygen (O2) and Carbon Dioxide (CO2) are carried by red blood cells throughout the body as we exercise. NO acts as a regulator and opens small blood vessels to allow more oxygen to enter muscle tissue. High NO means more blood flow to the muscles. It’s more complicated than that in reality and NNOXX also emphasises that its product does not measure the same kind of NO derived from dietary nitrates like Beetroot juice.

Generally speaking, higher NO levels are better and NO levels can trend similarly to power or running pace. The interesting stuff comes when they don’t track each other and that can be for a variety of reasons. Those reasons are your limiter(s) and NNOXX can identify them and then you can train to correct them and monitor the improvement over time.

Here’s quite a long YouTube video from NNOXX where they review in detail my near-maximal, Half Marathon-like effort. Further below I add some wide-ranging comments on my test if you’d prefer to read something.

click to view

Test Purpose

I think I know what power/pace levels I can sustain for a half-marathon race in my current state of training. I wanted to make sure. This test was to push me close to my threshold and slightly beyond the power/pace that I think I can do in an HM. Basically, a controlled test to failure.

Test Conditions

On generally flat, paved surfaces in very cool, virtually windless conditions.


Pre-Test Build Up

I was ill a month or so ago with COVID-19 and have also managed a series of recent multisport races and 5Ks which have gone OK despite the illness. I did a short 3-day taper for this test which historically is enough to let me perform near my best. I felt fresh on the day.

I had poor sleep. My waking HRV test was below my usual range and not what I would expect.

I performed a barely adequate warmup, finishing 15-20 minutes before the test started.


My lead-up to the test and test nutrition can be assumed to be ‘correct’. These are also worth noting

  • I pre-loaded with Beetroot concentrate including a final dose at 6:15 am. It takes 2 and a half hours to get into my system where I can feel an effect and it does make me faster. NNOXX do not expect to see the effect of dietary nitrate ingestion.
  • I had the correct dose of caffeine about an hour before the start. I do respond to caffeine well with the AA-type gene shared by 60% of us. It does notably elevate my HR by at least 5bpm
  • I used fructose/glucose gels correctly. My blood glucose would have been in Supersapiens “performance zone” had I been wearing their product.
  • I was more than sufficiently loaded with salts and was fully hydrated.


I intended to test my threshold. Consequently, I started off at a pace/power that I hoped I could maintain but doubted I would be able to.

Test Results

I succeeded in breaking myself too early and hence failed to optimise my power/pace for the duration. I proved my sustainable performance level was, in fact, roughly where I thought it was and not where I hoped it was!

My take on the test results is as follows, I’m specifically not referring to the NO and SmO2 analyses which are detailed in the YouTube video above.


  • At the end, I was done for. It was 98-99% of what I could possibly have achieved in terms of exertion.
  • After 30 minutes I felt I could not maintain the planned effort for much longer, I eased off slightly
  • I wasn’t out of breath
  • My Heart rate rose as I would expect peaking at 166. I don’t know my caffeinated LTHR at the moment but maybe it’s lower than 166. I’d determined it as about 163-164bpm for most of this year for my training zones, and today’s test seemed to confirm the same. My recent HRmax in a 5k was 180 bpm. My HRmin is in the mid to high 40s.
  • My form power was stable for the entire race according to Stryd ie the power required to make my technique function.
  • My vertical oscillation declined progressively
  • My leg spring stiffness was pretty stable with a very slight decline
  • My GCT gradually increased after about 30 minutes
  • My cadence was consistent


A Brief Overview of the NNOXX Data

I’ve divided the NO and SmO2 tracks into 5 visual phases.

  • The first phases clearly show that I wasn’t fully warmed up.
  • Phase 3 shows a better state where the balance has shifted toward oxygen supply
  • Phase 4 shows the progressive onset of fatigue
  • Phase 5 shows a point where blood flow and oxygen can be increased no more. A Plateau

The answer to “So what?” is in the video!

NNOXX One High Performance Platform
NNOXX One High Performance Platform

for completeness here is my HR track and power track from Garmin Connect

How can I Improve through training?

NNOXX identified my physiological limitation to improving my VO2max. There are 3 general limitations and the one most relevant to me is a Cardio Vascular Limitation which in part is evidenced by the NO plateau towards the end – it’s a delivery limitation.

Obviously, higher Zone 2 training volumes will help improve my performance and go some way to addressing my limitations. But what else?

NNOXX Recommendation: One way to improve maximal cardiac output is to use gradual desaturation training to progressively deoxygenate the muscle and at the same time to maximise NO. Once NO and SmO2 are stable then stop.

Such training would be generally classed as developmental in the physiological sense but the specific of the work would be similar to km or mile reps but with a key difference. The key difference would be a progressive increase in pace/power over a 2-6″ work period to the point where the fall in SmO2 and rise in NO both stop, followed by a full recovery. My personal take would be that this is one way to reach the point of maximum NO stimulus but with less fatigue per rep, hence increasing the ability to perform more reps.

More: nnoxx.com

How Will I Know I’ve Improved?

I will get faster!

Also the markers that show improvement will be the SmO2/NO levels at a given power work level.



I believed my limiter to be a weakness in clearing lactate at threshold-like levels.

My perception of my limiters was incorrect. A great anecdote from Evan@NNOXX was that it is often the case where people’s perceived limiters are actually their strengths. It’s just that their strength is used to compensate for all the effects of their weaknesses and is the last thing to give way. As that is what manifests itself at the point of failure, we assume it’s the problem.

More: nnoxx.com




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13 thoughts on “NNOXX One analysed my half marathon effort – here is exactly what they found

  1. Are nnoxx now shipping to the Uk? When I asked previously they say they didn’t have a distributer in Europe and the app is also not available in the store.

  2. What happens outside the subscription, can it still take readings, just not give the training plans?
    Are the readings available locally via a ciq datafield, in case the company goes out of business as so many do?

      1. I’m still using my old human hex long after the company went bust, because it adhered to the ANT+ spec and talks direct to the Garmin.

  3. interesting, especially the thing with NO, you know the book “Breath” of James Nestor, there are totally strange things explained with NO?

    1. hi thank you for that
      no i dont know the book
      nitrogen is pretty fundamental to life
      there are some interesting things that change with controlled breathing (I think there are nitrogen receptors in the nose) but it’s sometimes difficult to disassiciate what really happen from nonesense that fills the holistic/alternative space.

      1. I can only recommend the book, especially the different breathing techniques are very interesting, I’ve been doing this for some time and it helps me, it also helps me sleep better.
        Although I don’t yet know 100% what influences sleeping better, because after the book I studied Wimhof (Breathing), which is also recommended in the book and he also recommends cold showers, which I now do before going to sleep.


        There is also an iOS and Android App where you can try the breathing exercise and so on

  4. Do you think much of the result might be genetic, or as a result of a training plan.

    For instance, if a group of us, of similar ability followed the same training plan might we have similar results?
    And if so, could you then use NNOXX to build a better ‘generic’ training plan.

    And, can I blame my coach for any under-performance…

    1. We could have a similar ability but for different reasons. at least thats true at our kind of levels.

      nnoxx would guide you towards more beneficial workouts to counter your individual weaknesses. but I guess it (SmO2/NO) would help moderate generic efforts more ‘accurately’ to what is going on in our bodies than simple HR/power.

      it’s also interesting to use supersapiens. even for shorter races like 5k, it’s good to know if your are in what the company call its performance zone ie is there enough fuel/sugar to burn in the blood.

  5. Looking at NNOXX website, I am a bit puzzled by what exactly means the membership for the “One” subscription. The “Elite” gives an access to a web-based “High Performance Platform” (HPP) which looks as basic as possible, but at least there is something. Would you be able to comment on the difference between One and Elite subscription? Thanks!

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