Changes in cardiac contractility during graded exercise are greater in subjects with smaller body mass index, and greater in men than women: analyses using wave intensity and force–frequency relations

Introduction and purpose Estimation of the contractility of the left ventricle during exercise is an important part of the rehabilitation protocol. It is known that cardiac contractility increases with an increase in heart rate. This phenomenon is called the force–frequency relation (FFR). Using wave intensity, we aimed to evaluate FFR noninvasively during graded exercise.