IJCS | Volume 32, Nº4, July/August 2019

380 Belli et al. Speed and grade increment during cardiopulmonary Int J Cardiovasc Sci. 2019;32(4):374-383 Original Article and this is associated with greater oxygen deficit. 21 Moreover, uphill running is associated with greater glycogen depletion in the lower extremities. 33 Therefore, the grade-based protocol used in the present study probably resulted in the activation of a larger muscle mass, greater glycogen utilization, and earlier blood lactate accumulation, resulting in a lower VO 2 at the ventilatory thresholds. Some investigators have suggested that the prescription of exercise intensities for aerobic training using ventilatory (or blood lactate) thresholds as the reference is more physiologically sound than using a percentage of VO 2 max or a percentage of maximal HR. 4,6,34 Despite the fact that there are few data from controlled studies to support this strategy, 35 the concept that individuals with different ventilatory thresholds may exhibit different metabolic and cardiorespiratory responses to exercise at a given percentage of VO 2 max is well established. 4,6,13,34 Therefore, we compared metabolic and cardiorespiratory responses during exercise sessions with the intensities determined on CPET based on either speed or grade increments. As is commonly done in practice, exercise intensity was Figure 3 - Oxygen consumption and heart rate responses at four points during the maximal exercise tests with the speed and grade protocols. Data are expressed as mean +/- SE. VT 1 : first ventilatory threshold; VT 2 : second ventilatory threshold. * p < 0.01 between protocols.