What is happening in your muscles?
NIRS (Near-Infrared Spectroscopy) measures muscle oxygenation in real time. With the MOXY sensor, we can see how your muscles consume and regenerate oxygen — information that is inaccessible without this technology.
A window into your muscles
NIRS uses near-infrared light that penetrates muscle tissue. The sensor measures how much light is absorbed by oxygenated hemoglobin and from this calculates muscle saturation (SmO2).
This tells us whether your muscles receive enough oxygen during exertion, how quickly they regenerate between intervals, and where your local muscular capacity is limited.
When is NIRS useful?
Interval optimization
Determine ideal interval and rest duration based on SmO2 response.
Limiter identification
Are you limited by your heart/lungs or local muscular capacity?
Asymmetry detection
L/R muscle comparison — asymmetry can indicate uneven muscle loading or a clear difference in muscle perfusion.
SmO2 during exertion
Typical muscle saturation response during an interval.
Baseline SmO2 — your normal muscle saturation at rest (~60-80%)
Desaturation — during exertion SmO2 drops because muscles consume oxygen faster than they receive it
Recovery — after the interval SmO2 rises. Faster recovery = better fitness
NIRS / MOXY packages
NIRS Test
Standalone NIRS test with MOXY sensor.
- Step test or 5/1/5 custom test
- SmO2 and tHb analysis
- Recovery assessment
- PDF report with analysis and plan to address identified limiters
INSCYD + MOXY
Complete metabolic profile with muscle oxygenation.
- INSCYD LA test
- MOXY monitoring during test
- Full metabolic profile
- SmO2 thresholds
Frequently asked questions
Pulse oximetry (finger) measures arterial saturation — how much oxygen is in the blood. NIRS measures muscle saturation — how much oxygen your muscles are actually using. This is much more relevant for training.
Most commonly on the vastus lateralis (outer thigh). For cycling, this is the most relevant muscle. It can also be placed on the calf for running or the triceps for swimming.
Yes! MOXY is designed for use during workouts. It connects to Garmin, Wahoo, and other devices via ANT+.
NIRS measures up to ~15mm depth. With a thicker skin fold over the muscle, measurements are less accurate. For most athletes, this is not an issue.
Look inside your muscles
Book NIRS testing and discover what is happening beneath the surface.