Cardiac Responses to Endurance Exercise: Novel Insights from Exercise Speckle-Tracking Echocardiography and High-Sensitivity Cardiac Troponin Assays

Abstract

Endurance exercise training stimulates numerous adaptive changes to the structure, morphology and function of the human heart. Recent evidence suggests that a prolonged and strenuous bout of exercise, such as an ultra-endurance marathon or triathlon event, may results in temporary autonomic, biochemical and functional abnormalities which predominantly arise in the right ventricle. The impact of routine day-to-day endurance exercise training on exercise-induced cardiac disturbances is less clear, but likely influenced by hemodynamic, hormonal and metabolic factors that are related to the exercise intensity and duration. This thesis aimed to determine the time-course development (throughout exercise and during recovery) of cardiac perturbations evoked by exercise bouts that are typical of day-to-day endurance training. Indices of cardiac electrical conduction (atrial and ventricular conduction dynamics), autonomic activity (heart rate variability), ventricular mechanical function (left and right ventricular strain), and biomarkers of cardiac injury (serum cTn T & I) were examined in a cohort of recreationally active and trained men. The assessment of ventricular mechanical function during exercise is a key element of this thesis that enabled the exploration of functional cardiac limitations throughout and following endurance exercise. To determine the magnitude and time-course of exercise-induced functional and biochemical cardiac perturbations a laboratory based study was used to manipulate exercise intensity and duration while holding total mechanical work constant.