Reliability and Validity of Ventilatory Threshold and Respiratory Compensation Point Determined by Near‐infrared Spectroscopy

Abstract

The purpose of this study was to investigate the reliability and validity of ventilatory threshold (VT) and respiratory compensation point (RCP)determined by near‐infrared spectroscopy (NIRS). One hundred healthy sedentary males performed the grade exercise test (GXT) using a bicycle ergometer. An NIRS was employed to assess oxygenation (Δ[O2Hb]VL) in vastus lateralis muscle, whereas VT and RCP were determined by an automatic gas analysis. The results showed that variables VT and RCP determined by ventilatory analysis were significantly associated with changes of exercising Δ[O2Hb]VL measured by NIRS. The first and secondary timing points of declined Δ[O2Hb]VL during GXT reflected high coefficients of determination for VT (R2 = 0.88, P<0.05) and RCP (R2 = 0.89, P<0.05), respectively. Furthermore, the values of VO2 at VT and RCP measured by gas analysis were not significantly different from those variables determined by NIRS method.Additionally,the values of VT and RCP obtained from ventilatory and hemodynamic methods were highly reproducible day to day, and the single‐measure intraclass corrections were 0.93 to 0.95.Hence, we conclude that the analysis of NIRS is reliable and valid to determine VT and RCP during GXT.