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The cardiopulmonary exercise test (CPET) provides an objective assessment of ventilatory limitation, related to the exercise minute ventilation (V_E) coupled to carbon dioxide output (V_CO2) (V_E/V_CO2); high values of V_E/V_{CO2 slope} define an exercise ventilatory inefficiency (EV<i>in</i>). In subjects recovered from hospitalised COVID-19, we explored the methodology of CPET in order to evaluate the presence of cardiopulmonary alterations. Our prospective study (RESPICOVID) has been proposed to evaluate pulmonary damage’s clinical impact in post-COVID subjects. In a subgroup of subjects (RESPICOVID2) without baseline confounders, we performed the CPET. According to the V_E/V_{CO2 slope}, subjects were divided into having EV<i>in</i> and exercise ventilatory efficiency (EV<i>ef</i>). Data concerning general variables, hospitalisation, lung function, and gas-analysis were also collected. The RESPICOVID2 enrolled 28 subjects, of whom 8 (29%) had EV<i>in</i>. As compared to subjects with EV<i>ef</i>, subjects with EV<i>in</i> showed a reduction in heart rate (HR) recovery. V_E/V_{CO2 slope} was inversely correlated with HR recovery; this correlation was confirmed in a subgroup of older, non-smoking male subjects, regardless of the presence of arterial hypertension. More than one-fourth of subjects recovered from hospitalised COVID-19 have EV<i>in</i>. The relationship between EV<i>in</i> and HR recovery may represent a novel hallmark of post-COVID cardiopulmonary alterations.