Reference values for triceps surae tissue oxygen saturation by near-infrared spectroscopy

Objective.To establish the reference values for peripheral tissue perfusion of the triceps surae muscle assessed by Near-infrared spectroscopy (NIRS) at rest and in progressive effort.Approach.A total of 288 apparently healthy individuals of both sexes were included; between 30 and 79 years of age; nonsmokers; without diagnosis of diabetes mellitus, systemic arterial hypertension, kidney disease, symptoms of angina and intermittent claudication, or any musculoskeletal alteration that would prevent physical exertion; and without diagnosis of Peripheral arterial disease (PAD) or other associated symptoms. All individuals performed anthropometric measurements, physical activity levels, and tissue oxygen saturation (StO₂) assessments by NIRS during and after arterial occlusion maneuver and incremental shuttle walking test. The variables obtained by NIRS were presented in percentiles (P) for general comparison between sexes and for comparison between sexes according to age group. The relationship between the NIRS data and other variables was tested.Main results.Considering P50 and p<0.05, men had lower StO2 values, higher deoxygenation and reoxygenation (Tx-reox) rates at rest, and higher Tx-reox during progressive effort. There were correlations (p<0.0001) of body composition with the lowest StO2 and Tx-reox values and of functional capacity with Tx-reox in occlusion and Tx-reox.Significance.The percentiles presented can clinically assist in the diagnosis and monitoring of different health conditions; however, it is important to consider the individual's sex, body composition, and functional capacity.