Changes of stroke volume (SV, A), heart rate (HR, B), cardiac output (Qc, C), arterio-venous oxygen content difference (A-vDO2, D), mean arterial pressure (MAP, E), and total peripheral resistance (TPR, F) in relation to changes of oxygen uptake (VO2) during upright treadmill exercise in healthy sedentary individuals and patients with POTS before and after 3-month endurance training. Adapted with permission from Shibata et al (Shibata et al., 2012).