The Humon Hex uses near-infrared spectroscopy to measure the hemoglobin saturation in muscles (also referred to as SmO2).

LEDs emit light into the tissue and detectors measure the intensity of light that propagates through the muscle.

Since oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) have different absorption spectra in the near-infrared wavelength range, the SmO2 can be calculated.