Numerous studies have observed cardiac biomarker release with prolonged exercise. Despite this, we are unsure as to the constituent aspects of any given exercise bout that may be important in promoting cardiac biomarker release. This study examined the influence of exercise duration and intensity on the appearance of cardiac biomarkers. Twenty-one subjects ran for 45, 90 and 180 min at 85% and 95% of their individual anaerobic threshold on six different days randomized. Cardiac troponin I (cTnI) and N-terminal pro-brain natiuretic peptide (NT-proBNP) were assayed from blood samples collected before, 30 min and 3 h post-exercise. NT-proBNP was elevated after all exercise trials (range before: 21-32; range post: 38-67 ng/L). Peak post-exercise concentrations of NT-proBNP were associated with exercise duration (P=0.049), but not exercise intensity (P=0.451). cTnI was elevated after all exercise trials (range before: 0.007-0.011; range post: 0.008-0.021 μg/L). Peak post-exercise concentrations of cTnI were associated with exercise duration (P=0.003) and intensity (P=0.037). Data suggest that while both cTnI and NT-proBNP increased after all exercise trials, the mediating effect of duration influenced both NT-proBNP and cTnI while intensity influenced only cTnI.

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.