What is Muscle Oxygenation?

Muscle oxygenation is the percentage of blood in the muscle that is carrying oxygen.

Muscle oxygenation, or SmO2, is an important indicator of metabolic activity and provides insights into how well a muscle is functioning.  

For example, SmO2 reflects the dynamic balance of oxygen supply and delivery in muscles and how efficiently the body uses its energy reserves during exercise.

When exercising, muscles need oxygen to function properly. When there’s insufficient oxygen present in the muscle, performance is significantly reduced.

For athletes, muscle oxygenation is a key performance indicator.

Tracking muscle oxygenation (SmO2) can help athletes understand how their body responds to different types of exercise and make informed decisions about training intensity and duration, recovery, and other factors impacting performance. Additionally, SmO2 gives a more reliable indicator of physical exertion than heart rate (HR).

In a recent study, titled Near-Infrared Spectroscopy: More Accurate Than Heart Rate for Monitoring Intensity in Running in Hilly Terrain, scientists found that while heart rate was unaffected by continuous changes in terrain and intensity during exercise, muscle oxygenation (SmO₂) reflected these changes and strongly correlated with changes in oxygen consumption. These findings suggest that SmO₂ may offer a more accurate alternative to HR for monitoring exercise intensity, particularly over mixed terrain.

For trainers, muscle oxygenation provides active insights.

Coaches and trainers should track their client's muscle oxygenation (SmO2) levels to monitor their athletes' performance, recovery, and ability to utilize oxygen in exercising muscles — NNOXX is built to do exactly that.

Muscle oxygenation provides trainers insight into how their clients respond to different exercise protocols, allowing them to make adjustments to optimize performance.

This information can also help trainers make informed and effective decisions on workout intensity and provide insight into a person's overall health and fitness.

I've heard of blood oxygenation (SpO2). Is that the same thing as muscle oxygenation (SmO2)?

Need more science?

Read on.


While pulse oximetry measures blood oxygenation (SpO2), NNOXX measures the amount of oxygen delivered to muscles (SmO2). The difference is that SmO2 reflects the dynamic balance of oxygen supply and delivery in muscles, while SpO2 measures the amount of oxygen present in arterial blood.

Additionally, SmO2 indicates how much oxygen is being utilized by the muscle cells to generate energy for exercise or any other activity, while SpO2 does not.

What about VO2? How is that different from what NNOXX provides?

VO2 is a measure of the total amount of oxygen used by the whole body for energy.

VO₂ measurements have become common for people to quantify their intensity during exercise. Some of this is due to the growth in VO₂ features on popular wearable devices.

However, measuring VO₂ is not a simple task. Accurately measuring VO₂ requires users to wear a cumbersome mask over their face, and wearable devices that display VO₂ measurements provide estimates based on the user's heart rate, which have questionable accuracy.

The NNOXX wearable, on the other hand, directly measures muscle oxygen saturation (SmO₂) in exercising muscles, giving athletes an indication of when they need to rest or alter exercise intensity to prevent fatigue and optimize performance.

VO₂, on the other hand, measures total body oxygen use and does not directly quantify muscle performance and fatigue.