NNOXX One Review – Next-gen Sports Physiology Insights

Let’s take a good look at the NNOXX muscle oxygen and nitric oxide sensor in this relatively short review. It’s a unique product, designed to give athletes next-gen insights in an easy-to-wear, easy-to-use, sensor package.

Let’s start with a summary review, followed by a more detailed look at NNOXX One. If you’ve just come here for a discount on NNOXX One then follow this link to get one automatically applied at checkout on NNOXX.COM.

Simplistic Intro: oxygen burns carbs to release energy. Oxygen in muscles is termed SmO2. Nitric Oxide regulates the size of blood vessels…bigger=better.

Let’s go…

NNOXX Product Design

The NNOXX sensor is about half the size of a credit card and is half an inch thick (30mm x 74.5mm x 14.7mm). There is an LED and easy-to-press button on one side and a sensor array on the reverse. Charging is via a USB-C port at the end of the sensor.

It comes with a neatly designed velcro strap to securely hold it in place during exercise and some subtle design elements on the strap restrict its movement and restrict the ingress of ambient light – both good features!

I used the straightforward iOS partner app and had access to premium analysis on the online platform.

NNOXX Key Features

• Using in a workout and analysing afterwards
• AI Coaching
• Interpreting SmO2/NO states
• Training Load, Efficiency & Effectiveness

Deep Dive: Usability

NNOXX is easy to use.

Linking to the app and starting a workout is easy. However, for consistent results on any given muscle group you need to wear the sensor in almost the same place each time. This is tricky to precisely achieve for NNOXX and its competitor Train.Red. Another competitor, Moxy Monitor, sells apparel that includes a sensor mount giving more consistency to the positioning.

A further issue comes with the sensor moving during exercise. The NNOXX strap combined with my tight lycra shorts generally did a reasonable job of keeping NNOXX in place however I did sometimes experience downward slippage especially when running and sometimes saw noticeable changes in SmO2 levels when that happened.

I tended to use unguided sessions, looking at data on the NNOXX app – but more as a complementary aid to my other stats rather than following AI-guided workouts. NNOXX was often useful to me as an indication of when I was nearing my limits or confirming that I was at a stable level. That is similar to how I would use Moxy except that with Moxy its data can be displayed on one of my Garmin devices.

Train.Red is more like NNOXX in its reliance on its own app but does link to Garmin a bit. A big win for Train.Red during workouts is its smart recovery feature which tells you when to crack on with the next interval as well as analysing the types of recoveries you had between intervals.

Generally though, if you’re looking for a straightforward tool to accompany, say, a strength workout where you might be following a set on paper, NNOXX adds quite a bit of value as an app to help your execution.

There were quite a few times when NNOXX had no charge left when I wanted to use it. I hadn’t turned it off and it would benefit from an auto-off feature when not in use.

Deep dive: AI Coaching

The AI-guided workouts were simple to follow and the instructions were clear. Although I’m unsure to what degree they were AI/ML-based. For an endurance workout, all I had to do was specify a duration of 20, 40 or 60 minutes. There is no scope for athletes to link in external power or HR data.

The charts shown at the end of the workout for each measure are descriptive but not as insightful as they could have been. contrast to Train.Red, whose post-workout charts have the line colour-coded to the state of the muscle at that moment in time. Perhaps those details might be interesting for a while but as you use the app over the months I felt more drawn towards simple feedback. NNOXX now gives that with an Effectiveness and Efficiency score for your workout.

The following example shows some representative screens from two AI workouts that are illustrative of using the product. Most screens are from a super-easy workout which I performed efficiently however, because it was super easy, it wasn’t effective. At least that’s what NNOXX says in the final image.

Deep Dive: Interpreting SmO2/NO states

Sports physiology is complex and the SmO2/NO aspects of it are no exception. Understanding changes to SmO2 are hard enough and adding in changes to NO adds further context and insight. Even if you thought that could be easy, it’s further complicated by your change in effort. This table shows how to interpret the SmO2/NO changes when accelerating.

One of the interesting things to pick up on here is that changes to your technique can have immediately quantifiable impacts. And if they can be quantified you can work towards optimising them…thus getting faster. Changes to technique will include things like changing your breathing rate and pattern, changing your running gait, increasing your cycling cadence, getting out of the saddle when cycling, and so on. For example, I have focussed on a certain breathing pattern for one minute whilst maintaining constant effort and my SmO2 rose by a couple of percentage points; making that a permanent change is another matter entirely. Or you can easily stand when cycling and even though you might be putting out more power you might see a fall in SmO2 on the measured muscle as you give that muscle some relief by activating other muscle groups.

More: Full pdf document that includes the effects of decreased effort and constant effort.

NNOXX SmO2, SNO-Hb (NO) Key Concepts

Apologies if that’s offended some sports physiologists. Try this instead

Nitric oxide does not release energy from haemoglobin itself but modulates the oxygen-carrying capacity of haemoglobin and influences oxygen delivery to tissues. By regulating blood vessel dilation, oxygen affinity, and mitochondrial function, NO indirectly supports energy metabolism in tissues by ensuring that an adequate oxygen supply is available for cellular respiration and ATP production. NO levels peak post-exercise.

Then, if you’re wondering about dietary nitrate and measuring the effects of beetroot juice, try this

Endothelial-derived NO is not measured by NNOXX. Instead red-blood cell-mediated NO (also known as SNO-Hb) release is measured and this is responsible for increasing blood flow & oxygen delivery in small blood vessels. This SNO-Hb is not a direct product of the nitrate-nitrite-NO pathway

Muscle oxygen saturation (SmO2), measures the percentage of oxygenated versus deoxygenated haemoglobin in your muscle tissue during exercise. It gives insights into your muscular endurance and ability to use oxygen aerobically versus anaerobically while working out. At rest, while standing, SmO2 might be around 80-95%. It decreases as you exercise harder since your muscles need more oxygen. Fitness training helps your muscles maintain a higher SmO2 during easier exercise by growing more blood vessels and mitochondria to deliver and use oxygen efficiently. As intensity rises toward your limit, SmO2 drops fast as oxygen demand outpaces supply, so staying higher shows better aerobic fitness. Plus, SmO2 bounces back quickly after exercising as your muscles re-oxygenate, meaning highly efficient recovery. Tracking SmO2 helps gauge exercise intensity, find your best training zones, and avoid overdoing it.

On zones and VO2, try this

VO₂ and energy expenditure values can be approximated using SmO₂ together with other physiological parameters and SmO₂ measurements can be a complementary parameter to discriminate aerobic workload and anaerobic workload in athletes. Source [PMC10108753]

and this

Muscle Oxygenation Unlocks the Secrets of Physiological Responses to Exercise. More [PMC8936169 ]

NNOXX and Training Load, Efficiency and Effectiveness

On the homepage of its app, NNOXX has some charts that show NO and other metrics over recent periods. Each metric offers novel insights into your sports physiology. For example, positively trending Peak NO will indicate increasing fitness as studies have found endurance athletes to have higher NO levels at rest compared to untrained individuals, indicating that the ability to produce NO is probably trainable.

Whereas total NO is solely related to muscular training load – although I don’t know if it would be a better measure than TL properly derived from HR or power. I guess both power and HR require your zones to be correct to estimate load, NNOXX using NO simply measures it directly. Thus, monitoring post-exercise NO could reflect cumulative training load over time and gradual increases may show improved vascular function. Spikes or sustained high NO without recovery may indicate overreaching and the need for reduced training stress.

Next comes NNOXX’s latest metrics that are determined for each muscle group with a score only given after 3 completed workouts for that muscle group. The effectiveness metric gauges the amount of nitric oxide (NO) generated per minute during your workout and is presented in the context of your normal ranges. The higher the number, the greater the effectiveness.  The efficiency metric considers the amount of NO to movement velocity. A higher efficiency score indicates that you’re producing more NO relative to velocity.

Efficiency and effectiveness scores are then used to provide a personalized workout recommendation. For example, previously high effectiveness but low efficiency suggests you could be training unsustainably and then the app may recommend reducing intensity or type of workout next time around.

Performance Tests

I am unable to directly overlay NNOXX data on the data I have for Train.Red and Moxy in the same workouts. It’s tricky to compare 3 sensors even if NNOXX did export the data. First up the readings are position-dependent and I would typically have one device on each leg and they are clearly assessing different muscles! Secondly, if they are on the same leg they get in each other’s way and the various light shields and straps around them stop them from being together and interrogating the same muscle. Even if they could be put close together the infrared light from each sensor is reasonably likely to interfere with the other sensor. #Amess.

Even if that could be sorted out Moxy, Train.Red and NNOXX interrogate to different muscle depths and at different frequencies. Heck Train.Red doesn’t look at SmO2 but rather TSI (relative concentration change of Tissue Oxygenation) and Moxy uses a completely different way (Monte Carlo simulation) to derive its final answers.

Here is one workout where I can show the 3 sensors working at the same time and recording data into their own apps, well into Golden Cheetah in the 3rd case for Moxy. I won’t even begin to try to compare the three other than to say that after a warmup, SmO2 falls as I try harder!

The differentiator for NNOXX is that it puts those changes into context with NO, whereas Train.Red and Moxy show you other muscle-oxygen-related metrics.

Here’s quite a long YouTube video from NNOXX where they review in detail my near-maximal, Half Marathon-like effort explaining what’s going on inside my body. For more context read this post.  I think this is probably data with a greater resolution than 1Hz data and that’s why the lines are blurred, kinda representing the max and mins at any one time as the muscle contracts.

Who should buy NNOXX? Target markets

Several types of customers might be interested in SmO2 and NO.

• Sports Labs – NNOXX is not ideal as there is currently no means to export data into other tools
• Pro Sports teams – I didn’t test the NNOXX One Team Platform
• Coaches – NNOXX can be used under instruction or on a one-to-one basis but results can’t be analysed in detail against other metrics the coach might be interested in (like a calibrated power source). Guidance on load and tweaks to workout protocols are aided by NNOXX data.
• Committed endurance athletes – great for indoor training where you can easily see live readings on the app. Can’t be easily used live for outdoor training and you must get the Elite version to analyse or export your data.
• Committed Cross Fitters – Great for optimised gym work and the odd bit of cardio. Like other tools, you’ll have to decide how often you want to move the sensor between muscle groups and how you will interact with the smartphone app at each workout station.

NNOXX One vs NNOXX One Elite – What’s the Difference?

The two sensors are identical.

However, the Elite version gives access to Internal Training Load, Movement Acceleration and Skin Temperature metrics plus access to the online High Performance Platform (analysis tool)

NNOXX – Use Cases, Things to Try

• Demonstrate the three possible muscle oxygenation trends – Perform biceps curls using the unguided workout mode. At rest, SmO2 is stable (adequate supply). Work for ten seconds, SmO2 will decline (increased oxygen use), relax and SmO2 will recover
• Demonstrate how NO changes dependent on need – Cycle using the unguided workout mode. The baseline NO will be close to zero. Cycle at a moderate to hard effort and NO level will increase, indicating an increased need to supply oxygenated blood to the working muscles. Relax and the NO level will decline to baseline.
• Determine easy, moderate, hard and maximal intensity ‘zones’ – Row using the unguided workout mode. Now, begin at a low intensity and observe SmO2 values. After a few minutes, repeat at a moderate intensity. repeat at a hard intensity. Repeat for 20-30 second maximal efforts. After you’ve rested, how high did it get back up to?
• Understand how cadence, breathing, and body position impact SmO2 – 10:00 Wattbike at 90-100% FTP, repeat 2 to 4 times. Start with normal relaxed breathing. Note SmO2 and your goal is to increase it at a constant power. Try to increase RR (breath frequency, not depth). Try higher and lower cadences and lower/higher resistances to match. Altering your ride position on the bike – drops, aerobars, hoods, bar tops – how does this impact your SmO2?
• Estimate SmO2 Training zones (this spreadsheet) – 60 seconds easy. 120 seconds moderate. 30 seconds hard. 90 seconds of complete rest. Note the lowest SmO2 level during the hard portion of the warmup and the highest SmO2 level during the rest period following. Use those values.
• Desaturation to increase mitochondrial density – Repeat to failure or 45 minutes: 10-second Echo Bike (70-75% of maximum wattage) or Concept II (80-85% max) or Ski ERG (90-95% max), Rest 1:00. Failure is when SmO2 cannot reach the same minimum value as previous sets during your sprint, or you cannot reoxygenate back to the same SmO2 value as previous sets during your recovery.
• Extended Desaturation to spend more time at higher intensities – Row 500m at 5s faster than 2k PR pace until SmO2 stops declining and levels off for 5-10 seconds. Rest until SmO2 stops increasing and reaches a recovery baseline. Repeat for 2-6 total sets.
• Gradual Desaturation to maximise cardiac output – 6:00 Echo Bike, Rest 4:00 x4 sets. Start each set at the same easy pace (say 130w) and progressively increase effort over the 6:00 minutes to finish within 5-10% of your minimum SmO2 value. Trial and error will be needed with the effort.
• Proper Active Recovery Avoiding De-Oxygenation – Exercise at a very low intensity. Initially, SmO2 falls then stabilises then rises slowly. When it gets to an extended plateau level for several minutes try to raise, but not lower this plateau with changes to cadence, and temporary small speed increases and rests.
• Assess Progression (Basic) – Determine a straightforward weekly test eg a 7:00/mile or 250w for 10 minutes. Nothing that is simple but that will not detract from your plan. NNOXX’s high-performance portal lets you compare the NO and SmO2 levels in these workouts to determine progression.
• Assess Progression (Advanced) – use the Work Score [watts / (100-SmO2)]. If you get better you either produce more power or produce the same power for less oxygen cost. Either is good.
  
• Determine Limiters –  What kind of limitation do you have in delivery, respiratory or utilisation? NNOXX has resources to specify the training each type of athlete should follow. Perhaps historically you have addressed specific power-duration limiters by working at percentages of those power-duration levels? Perhaps there are better ways to improve?

NNOXX Price Comparisons

NNOXX One appears expensive but it is a much cheaper SmO2 sensor than either Train.Red or Moxy. So there is a definite value argument in favour of it.

However, I don’t see the value in the Elite version that justifies a near-doubling of the price.

Take Out

I like the unique insights that the NNOXX sensor provides into nitric oxide in the body.

I love the relatively low-cost access to Muscle Oxygen (SmO2)

This novel data has a variety of scientifically sound applications in training and racing for endurance and strength athletes alike. Be that pacing endurance efforts, optimising recovery between sets, determining physiological training zones, discovering physiological limiters or quantifying and assessing progress.

Whilst the sensor is good to go, the product’s ecosystem and value proposition need more development. The company is working on that.

NNOXX One is probably never going to target the lab side of the market, so it must do a good job of helping CrossFit, weightlifting, and endurance athletes with their training. In its current format, I can only see CrossFit, HYROX, and weightlifters adapting their workout routines to follow the real-time guidance from the smartphone app.

If you are a Biohacker with cash to spend on a new and useful insight into your body then your Visa card awaits you. You won’t find the NO data anywhere else.

Endurance athletes probably need a product like this to follow Garmin data standards so the data can be displayed on a Garmin during workouts and exported in a standard format to third-party analysis tools afterwards. At a minimum, I would expect to see support for VO2master, and the ability for anyone, not just NNOXX One Elite owners, to export from the High Performance Platform (or app).

I fall into the latter category. Specifically, all that I would personally want would be a Garmin CIQ Data Field that showed my SmO2 and NO states, perhaps with a means of alerting me to impending failure, or a change of state like entering hypertrophy during recovery between sets. I would want to export the data into other tools like Golden Cheetah/Training Peaks where I could look at the data against data points from other power, HR and temperature sensors. I’m not so much interested in what NNOXX’s accelerometer says when I have several accurate power meters.  The mechanisms I already have for workout execution and data capture are just too complicated for me to change to rely on a 3rd party app. That’s just me though.

Unique Data Points | Useful, Insightful Data | Sensor needs greater Connectivity | Ecosystem needs more integrations & features

Buy: NNOXX One from $499