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The purpose of this study was to compare the acute cardiorespiratory responses and time spent above different %VO_2peak intensities between three “iso-work” protocols: (a) a high intensity interval training protocol (HIIT), (b) a higher intensity continuous protocol (CON₇₀) and (c) a lower intensity continuous protocol (CON₅₀) in patients with chronic heart failure (CHF). Ten male CHF patients (aged 55.1 ± 16.2 years) performed in separate days a single session of a HIIT protocol consisted of 4 sets × 4 min cycling at 80% VO_2peak with 3 min of recovery at 50% VO_2peak, a CON₇₀ protocol corresponding to 70% VO_2peak and a CON₅₀ protocol corresponding to 50% VO_2peak. Cardiopulmonary data were collected by an online gas analysis system. The HIIT and CON₇₀ elicited higher cardiorespiratory responses compared to CON₅₀ with no differences between them (<i>p</i> > 0.05). In HIIT and CON₇₀, patients exercised longer at >80% and >90% VO_2peak. The completion rate was 100% for the three protocols. Not any adverse events were observed in either protocol. Both HIIT and CON₇₀ elicited a stronger physiological stimulus and required shorter time than CON₅₀. Both HIIT and CON₇₀ also induced comparable hemodynamic responses and ventilatory demand.