Heart failure (HF) patients traditionally report dyspnoea as their main symptom. Although the cardiopulmonary exercise test (CPET) and 6 min walking test are the standardized tools in assessing functional capacity, neither cycle ergometers nor treadmill maximal efforts do fully represent the actual HF patients’ everyday activities [activities of daily living (ADLs)] (i.e. climbing the stairs). New-generation portable metabolimeters allow the clinician to measure task-related oxygen intake (VO2) in different scenarios and exercise protocols. In the last years, we have made considerable progress in understanding the ventilatory and metabolic behaviours of HF patients and healthy subjects during tasks aimed to reproduce ADLs. In this paper, we describe the most recent findings in the field, with special attention to the relationship between the metabolic variables obtained during ADLs and CPET parameters (i.e. peak VO2), demonstrating, for example, how exercises traditionally thought to be undemanding, such as a walk, instead represent supramaximal efforts, particularly for subjects with advanced HF and/or artificial heart (left ventricular assist devices) wearers.