IJCS | Volume 32, Nº4, July/August 2019

376 Belli et al. Speed and grade increment during cardiopulmonary Int J Cardiovasc Sci. 2019;32(4):374-383 Original Article (Micromed-Biotecnologia, Brasília, Brazil). Perceived exertion using the 0 to 10 Borg scale 25 was obtained every 2 min. Gas exchange variables were measured breath-by-breath by a validated system (Metalyzer 3B, CPET System, Cortex, Leipzig, Germany) and expressed in 20s intervals. 26 VO 2 max was defined as the highest value measured for a period of 20s during the CPET. VT 1 and VT 2 were determined by visual inspection. VT 1 was identified as the VO 2 or HR immediately before a systematic increase in the ventilatory equivalent for oxygen (minute ventilation [VE] / VO 2 ), without an increase in the ventilatory equivalent for carbon dioxide (VE / carbon dioxide output [ ECO 2 ]). 3,27 The V-slope method was also used to confirm the VT 1 . VT 2 was identified as the point immediately before a systematic increase in VE/VECO 2 , usually at the same time that the end-tidal CO 2 decreased systematically. 3 All ventilatory thresholds and VO 2 max evaluations were determined by the same experienced researcher, who was blinded to the protocols. Exercise prescription The exercise intensity during the submaximal exercise sessions was based on the HR corresponding to the mean point between VT 1 and VT 2 , obtained from the speed and grade protocols. During submaximal exercise sessions, Figure 1 - Increments in speed and grade during the speed and grade protocols.