ORIGINAL RESEARCH Cardiac Biomarkers and Exercise Duration and Intensity During a Cycle-Touring Event Enrique Serrano-Osta´riz, PhD,* Alejandro Legaz-Arrese, PhD,* Jose´ Luis Terreros-Blanco, PhD,† Marta Lo´ pez-Ramo´n, PhD,‡ Daniel Cremades-Arroyos, PhD,* Silvia A ´ lvarez-Izquierdo, PhD,§ and Pilar Boscos-Terraz, PhD§ 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 imme- diately post race, with 43% of participants exhibiting cTnI levels greater than 0.04 mg/L and 65% of the participants measuring NT- pro-BNP levels greater than 125 ng/L. The cTnI increase was sig- nificantly 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 = 20.36, 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 re- sponsible for the increase in NT-pro-BNP. Future standardized en- durance 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. Key Words: cardiac marker, exercise, myocardium (Clin J Sport Med 2009;19:293–299) INTRODUCTION Cardiac-specific troponins (cTnT and cTnI) are the accepted standards to serologically identify myocardial damage and are used clinically to diagnose acute myocardial infarction. 1 Elevated concentrations of N-terminal pro-brain natriuretic peptide (NT-pro-BNP) reflect elevated myocardial wall stress by myocyte stretch due to volume or pressure overload in cardiac dysfunction, congestive heart failure, cardiomyopathy, and other cardiac diseases. 2 An increasing number of studies have shown that prolonged strenuous exercise promotes the elevation of these cardiac biomarkers. 3–7 As a consequence, an intense debate has developed over the clinical repercussions of recreational athletes competing in long-distance events. 3–5,8 Although the clinical significance of the increase in cardiac-specific biomarkers after strenuous endurance exercise in healthy athletes is unclear, it is of interest to determine the importance and role of factors that may promote biomarker release. Importantly, Neilan et al 8 observed that NT-pro-BNP and cTnT increases were inversely correlated with the weekly amount of training time. In addition, a weak association between post-marathon NT-pro-BNP and training time has been previously reported. 3 Ko¨ nig et al 9 found that professional cyclists had normal post-exercise cTnT levels and that all participants who exhibited BNP levels above the upper reference limits (URLs) were older than 30 years. Age- dependent increases in post-race NT-pro-BNP have been found in other studies. 10,11 The influence of exercise duration and intensity on cardiac-specific biomarker release is poorly understood and controversial. The increase in NT-pro-BNP has been associ- ated with exercise duration. 12 Interestingly, Scharhag et al 13 reported that NT-pro-BNP concentrations are similarly in- creased by 30 minutes of moderate and brisk walking in patients with coronary artery disease. On the other hand, in individual competitions, exercise duration has not been associated with increases in cTnI or cTnT, 8,11,12 but a recent meta-analysis reported that the detection of post-exercise cTnT decreased slightly as the event duration increased, 14 a finding Submitted for publication January 27, 2009; accepted April 8, 2009. From the *Section of Physical Education and Sports, University of Zaragoza, Zaragoza, Spain; †Sports Medicine Center, Arago´n Government, Zaragoza, Spain; ‡Service of Cardiology, Miguel Servet University Hospital, Zaragoza, Spain; and §Service of Biochemistry, Miguel Servet University Hospital, Zaragoza, Spain. The authors state that they have no financial interest. Reprints: Enrique Serrano-Osta´riz, PhD, Facultad de Medicina, C/Domingo Miral S/N, Zaragoza 50009, Spain (e-mail: enrise@unizar.es). Copyright Ó 2009 by Lippincott Williams & Wilkins Clin J Sport Med  Volume 19, Number 4, July 2009 www.cjsportmed.com | 293