Muscle Oxygenation is a measurement of how much hemoglobin is carrying oxygen in the capillaries of the muscle. It is expressed as a percentage from 0 to 100 and is often abbreviated as SmO2.
Muscle Oxygenation is a localized measurement that depends on the exertion level, blood flow, and relative changes in the hemoglobin dissociation curve. It is measured optically with near-infrared light, so it is completely non-invasive.
The different absorption spectra of the infrared light passing through the muscular tissue can identify the relative amount of hemoglobin that is carrying oxygen compared to the amount that is not.