Figure 2. Oxygen uptake (VO2, panel A), carbon dioxide output (VCO2, panel B), ventilation (VE, panel C), and respiratory exchange ratio (RER, panel D) responses during the 30/30 s and the 60/60 s low-volume high-intensity interval training (LV-HIIT) protocols. Values are presented as mean ± SD. (a) difference between LV-HIIT protocols to the same time point. (b) difference intra-60/60 s LV-HIIT protocol related to the first time point. (c) difference intra-30/30 s LV-HIIT protocol related to the first time point. (*) compared to the same time point of the 30/30 s LV-HIIT protocol, main effect of protocol by ANOVA.