Physiological differences in cardiovascular hemodynamics across treadmill and cycle exercise as assessed through impedance cardiography

Impedance cardiography (IC) measures cardiovascular hemodynamics non-invasively during exercise. However, IC measurements assessing physiological differences across treadmill (TM) and cycle (CYC) exercise has not been investigated. The purpose of this study is to investigate whether hemodynamic measurements assessed via IC are consistent between TM and CYC exercise at two absolute exercise intensities. Twenty-one men (age = 21.4 ± 0.5 y; BMI = 24.4 ± 0.5) completed four exercise tests, two TM and two CYC. Within each test, two, five-minute, steady-state stages were completed with targeted intensities of 5 (MODex) and 7 (VIGex) metabolic equivalents (METs). Oxygen consumption (VO2) was measured by indirect calorimetry. Hemodynamic measures were obtained via IC (PhysioFlow, PF07 Enduro) and included cardiac output (CO), heart rate (HR), stroke volume (SV), end diastolic volume (EDV), ejection fraction (EF), systemic vascular resistance (SVR), contractility index (CTi), and left cardiac work index (LCWi). Within treadmill exercise, there were no main effects for trial, except for HR. There were no main effects for trial within CYC exercise. Across exercise modes, there were no significant differences between TM and CYC exercise for all variables, with the exception of higher HR in CYC, and higher SV and EDV in TM. ICCs were strong for all variables except VIGex SVR and VIGex LCWi. IC hemodynamic measurements showed strong repeatability across modes for all hemodynamic variables during MODex. For VIGex, all variables showed strong correlations, except for SVR and LCWi. Lack of agreement may be associated with daily variation in hemodynamics or physiological differences across modes with the remainder of discrepancies associated with device error