Cardiovascular disease and cardiac complications are currently the most common comorbidities among patients with COVID-19. Although some hypotheses may justify it, the mechanisms of cardiac injury by the coronavirus are unclear. To evaluate the impact of COVID-19 on cardiac function, measured with a cardiographic impedance, in post-COVID-19 patients during the 1-minute sit-to-stand functional test (1-STS). Methods: This is a cross-sectional case-control case series study. The included subjects were divided into two groups: the post-COVID-19 group and the control group. We evaluated functional capacity using 1-STS, monitoring cardiovascular variables continuously and non-invasively using impedance cardiography (at rest, beginning, end, and recovery. Data were analyzed using the 2-way ANOVA test. Results: 47 individuals of both sexes, 36 in the COVID-19 group (40.17±13.04 years) and 11 in the control group (30.82±12.68 years) were included in the study. We found a reduction in mean performance in the 1-STS (p = 0.01) and a reduction in cardiac hemodynamic values in the COVID-19 versus control group between rest, beginning, end, and recovery in cardiac contractility indices (p group < 0.0001; p time <0.0001), and ejection fraction (p group <0.0001; p time = 0.0002) and an increase in systemic vascular resistance (p group = 0.0019; p time <0,0001). Conclusions: The results suggest that in post-COVID-19 patients, there is a reduction in the cardiac contractility index and ejection fraction with an increase in peripheral vascular resistance during the functional capacity assessment, which could explain the low functional performance during the 1-STS.