Respiratory threshold as a new threshold determination method based on respiratory responses and it’s success to indicate critical power

Abstract

The respiratory threshold (RT), introduced as a new threshold determination method that relied on respiratory responses, is based on the analysis of time-dependent changes in the ratio of minute ventilation divided by the end-tidal partial pressure of CO2 (VE/PETCO2) in an incremental ramp test. However, there is no research finding focusing on the level at which the RT technique can indicate the critical power (CP), which is an essential threshold determination method widely used. The aim of this study was to investigate at which level the exercise intensity obtained using the RT technique can meet the CP. Ten well-trained male cyclists participated in the study. Gas exchange threshold (GET), respiratory compensation point (RCP), and RT levels of the athletes were determined by incremental ramp tests. In those tests, GET and RCP were evaluated by detecting breakpoints obtained in relationships of VCO2-VO2 and VE-VCO2 using the Innocor system. The RT level was found by the strongest breakpoint in the VE/PETCO2-time relationship using SegReg software. Then, tests were applied at constant work rates on different days to estimate the CP. Validity analyses were performed to test the relationships of all threshold indicators with each other. Results showed a high correlation and concordance between RT (328±35.5 W; 4.23±0.39 L·min−1) and RCP (324±34.3 W; 4.21±0.45 L·min−1) power outputs and the VO2 responses of each (p>0.05; t= 1.19; r>0.96; estimated standard error %