Cardiac indexes, cardiac damage biomarkers and energy expenditure in professional cyclists during the Giro d'Italia 3-weeks stage race

Introduction: The study of cardiac response to strenuous and continuous exercise is crucial to understanding the physiology of endurance. N-terminal proB-type natriuretic peptide (NT-proBNP) is a potential marker for monitoring myocardial wall stress, and troponins (TnT and TnI) are widely used in the diagnosis of cardiac ischemia and infarction. Strenuous exercise may generate transitory ischemia, myocardial stress, and diastolic left ventricular dysfunction, inducing the increased production of both these biomarkers. We measured changes in NT-proBNP and TnT in elite cyclists during a 3-week stage race, a model of strenuous exercise. Materials and methods: The study population was 9 professional cyclists participating in the 2011 Giro d’Italia. Pre-analytical and analytical phases scrupulously followed official recommendations. Anthropometric data, net energy expenditure and cardiac indexes (rate, diastolic and systolic blood pressure) were recorded. Blood samples were drawn pre-race (day -1) and at days 12 and 22; NT-proBNP and highly sensitive-troponin (Hs-TnT) concentrations were assayed and corrected for plasma volume changes. Results: Body-mass index decreased and energy expenditure increased by 52% during the race. NT-proBNP concentrations increased [day -1: 23.52 ng/L (9.67-34.33); day 12: 63.46 ng/L (22.15-93.31); P = 0.039; day 22: 89.26 ng/L (34.66-129.78) vs. day -1; P < 0.001] and correlated with heart rate (r = -0.51; P = 0.006), systolic pressure (r = 0.39; P = 0.046) and energy expenditure (r = 0.70; P < 0.001). TnT concentrations did not vary, but a widened TnT amplitude distribution was observed. Conclusions: Increases in NT-proBNP correlated with higher energy expenditure over a 3-week cycling stage race, possibly indicating myocardial stress.