Cardiac biomarkers and exercise duration and intensity during a cycle-touring event.

Objective: To determine the influence of age, training status, race time, and exercise intensity on the appearance of cardiac biomarkers after a cycle-touring event.
Design: Pre-post exercise measurements.
Setting: University of Zaragoza, Zaragoza, Spain.
Participants: Ninety-one amateur cyclists.
Intervention: The 2005 Quebrantahuesos cycle-touring event (distance: 206 km; altitude difference: 3800 m).
Main Outcome Measures: Cardiac troponin I (cTnI) and N-terminal pro-brain natriuretic peptide (NT-pro-BNP) were measured the day before and immediately after the race. Heart rate (HR) monitoring was performed on 55 cyclists during the race to evaluate exercise intensity.
Results: cTnI and NT-pro-BNP were significantly elevated immediately post race, with 43% of participants exhibiting cTnI levels greater than 0.04 microg/L and 65% of the participants measuring NT-pro-BNP levels greater than 125 ng/L. The cTnI increase was significantly associated with mean exercise intensity HR (r = 0.36, P < 0.01) but was not associated with age, training status, or race time. The increase in NT-pro-BNP correlated with race time (r = 0.40, P < 0.001) and training status (r = -0.36, P < 0.001) but was not associated with age or exercise intensity HR measures.
Conclusions: These results suggest that, in part, exercise intensity (HR) is responsible for the cTnI increase and that race time is responsible for the increase in NT-pro-BNP. Future standardized endurance exercise trials are recommended to further elucidate the potentially differential effects of training status, exercise time, and intensity on post-exercise increases in cTnI and NT-pro-BNP.