Purpose: To compare the cardiorespiratory responses of a traditional session of high-intensity interval training session with that of a session of similar duration and average load, but with decreasing workload within each bout in cyclists and runners. Methods: A total of 15 cyclists (maximal oxygen uptake [$\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$] 62 [6] mL·kg⁻¹·min⁻¹) and 15 runners ($\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ 58 [4] mL·kg⁻¹·min⁻¹) performed both sessions at the maximal common tolerable load on different days. The sessions consisted of four 4-minute intervals interspersed with 3 minutes of active recovery. Power output was held constant for each bout within the traditional day, whereas power started 40 W (2 km·h⁻¹) higher and finished 40 W (2 km·h⁻¹) lower than average within each bout of the decremental session. Results: Average oxygen uptake during the high-intensity intervals was higher in the decremental session in cycling (89 [4]% vs 86 [5]% of $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$, P = .002) but not in running (91 [4]% vs 90 [4]% of $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$, P = .38), as was the time spent >90% of $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ and the time spent >90% of peak heart rate. Average heart rate (P < .001), pulmonary ventilation (P < .001), and blood lactate concentration (P < .001) were higher during the decremental sessions in both cycling and running. Conclusions: Higher levels of physiological perturbations were achieved during decremental sessions in both cycling and running. These differences were, however, more prominent in cycling, thus making cycling a more attractive modality for testing the effects of a training intervention.