Abstract

This study aimed to evaluate if the changes in oxygen saturation levels at intercostal muscles (SmO2 m.intercostales) assessed by near-infrared spectroscopy (NIRS) using a wearable device could determine the respiratory compensation point (RCP) during exercise. Fifteen healthy competitive triathletes (eight males; 29 +/- 6 years; height 167.6 +/- 25.6 cm; weight 69.2 +/- 9.4 kg; (V) over dotO(2)-max 58.4 +/- 8.1 mL.kg(-1).min(-1)) were evaluated in a cycle ergometer during the maximal oxygen-uptake test ((V) over dotO(2)-max), while lung ventilation ((V) over dotE), power output (watts, W) and SmO2 mantercostales were measured. RCP was determined by visual method (RCPvisual : changes at ventilatory equivalents ((V) over dotE.CO2-1, (V) over dotE.(V) over dotO(2)(-1)) and end-tidal respiratory pressure (PetO(2), PetCO(2)) and NIRS method (RCP NIRS : breakpoint of fall in SmO2 m.intercostales). During exercise, SmO2 m.intercostales decreased continuously showing a higher decrease when (V) over dotE increased abruptly. A good agreement between methods used to determine RCP was found (visual vs NIRS) at %(V) over dotO(2)-max, (V) over dotO(2), (V) over dotE, and W (Bland-Altman test). Correlations were found to each parameters analyzed (r = 0.854; r = 0.865; r = 0.981; and r = 0,968; respectively. p 0.001 in all variables, Pearson test), with no differences (p 0.001 in all variables, Student's t-test) between methods used (RCPvisual and RCPNIRS). We concluded that changes at SmO2 m.intercostales measured by NIRS could adequately determine RCP in triathletes.