Muscle Oxygen Saturation Measured Using “Cyclic NIR Signals” During Exercise

A new approach to measure muscle oxygen saturation (SmO2) using near infrared spectroscopy (NIRS) has been proposed in this paper. This approach exploits the cyclic NIRS signals seen during exercise which are often regarded as "movement artefacts". This new measure, which we term the "cyclic SmO2", has the potential to be less affected by the myoglobin which is traditionally believed to be indistinguishable from haemoglobin using NIRS techniques. The cyclic SmO2 also has fewer assumptions than the conventional SmO2 measured using time, phase and spatially resolved spectroscopy methods. In a cycling exercise study, NIRS measurements were made over the Vastus lateralis muscle of 11 subjects. In a light exercise protocol, the group mean of the conventional SmO2 was 51.7 ∼4.3% and that of the cyclic SmO2 was 56.0∼ 3.9%. It was immediately followed by a hard exercise protocol and the group mean of the conventional SmO2 was reduced to 42.6 ∼ 6.1% and that of the cyclic SmO2 to 48.5 ∼ 5.6%. The reduction agrees with the general expectation. The cyclic SmO2 is a promising new measure of muscle oxygenation. © Springer Science+Business Media, LLC 2010.