Author(s): BARAWI, S., HAPP, K.A., BEHRINGER, M., Institution: GOETHE UNIVERSITY FRANKFURT, Country: GERMANY, Abstract-ID: 1575

INTRODUCTION:
The MOXY is an innovative muscle oxygen monitor that uses near-infrared spectroscopy (NIRS) to measure local oxygen saturation (SmO₂) and total haemoglobin (THb). It continuously measures muscle oxygen saturation by emitting light beams into the muscle. The reflected light is collected by two sensor in near distance [1]. Since hemoglobin and myoglobin change their absorption of infrared light due to oxygenation, NIRS measurements can be used to estimate the oxygen saturation of the muscles (SmO₂). This study investigates the effect of subcutaneous femoral fat (SFF) on the accuracy of SmO₂ measurements, addressing a significant factor that can affect NIRS readings.
METHODS:
Forty participants (25.4 ± 3.5 years, 68.4 ± 13.1 kg, 173 ± 8.9 cm) had the Moxy device (Idiag AG, Switzerland) placed on the rectus femoris muscle. At 50% of the distance between the spina iliaca anterior inferior and the base oft the patella. Resting SmO2 values were recorded for 5 minutes, and the average of the last 2 minutes was analyzed. SFF thickness was measured using ultrasound (ACUSON Redwood, Siemens, USA). The linear transducer (2.9 – 9.9 MHz) head was placed vertically with as minimal pressure to prevent compression of the underlying tissue. SFF thickness was defined as the distance from the subcutaneous fat tissue-muscle interface to the subcutaneous fat tissue-skin interface. Three images were taken, and the average SFF in centimeters (cm) was used for further calculations.
RESULTS:
Linear regression analysis showed a moderate positive correlation between SFF in cm and SmO2 values (r = 0.437, p < .001). SFF in cm explained approximately 19.1% of the variation in SmO2 values. The regression coefficients showed that for every cm increase in SFF, SmO2 levels decreased by -1.67 % (intercept = 91.65, p < 0.001; SFF = -1.67, p = 0.005).
CONCLUSION:
These results show a clear influence of SFF on the SmO2 values, that needs to be taken into account when interpreting SmO2 values. The linear relationship shows that the data of MOXY device are impaired with increasing fat layer, reducing the validity of the information about the muscular SmO₂.Further research is needed to investigate whether the influence of subcutaneous adipose tissue can be mathematically calculated out to improve the accuracy of muscular SmO₂ measurements in people with elevated subcutaneous fat layers.

[1] Miranda-Fuentes, C.; Chirosa-Ríos, L.J.; Guisado-Requena, I.M.; Delgado-Floody, P.; Jerez-Mayorga, D. Changes in Muscle Oxygen Saturation Measured Using Wireless Near-Infrared Spectroscopy in Resistance Training: A Systematic Review. Int. J. Environ. Res. Public Health 2021, 18, 4293. https://doi.org/10.3390/ijerph18084293