Determinants of Interindividual Variation in Exercise‐Induced Cardiac Troponin I Levels

Background Postexercise cardiac troponin levels show considerable interindividual variations. This study aimed to identify the major determinants of this postexercise variation in cardiac troponin I (cTnI) following 3 episodes of prolonged high‐intensity endurance exercise. Methods and Results Study subjects were recruited among prior participants in a study of recreational cyclists completing a 91‐km mountain bike race in either 2013 or 2014 (first race). In 2018, study participants completed a cardiopulmonary exercise test 2 to 3 weeks before renewed participation in the same race (second race). Blood was sampled before and at 3 and 24 hours following all exercises. Blood samples were analyzed using the same Abbot high‐sensitivity cTnI STAT assay. Fifty‐nine individuals (aged 50±9 years, 13 women) without cardiovascular disease were included. Troponin values were lowest before, highest at 3 hours, and declining at 24 hours. The largest cTnI difference was at 3 hours following exercise between the most (first race) (cTnI: 200 [87–300] ng/L) and the least strenuous exercise (cardiopulmonary exercise test) (cTnI: 12 [7–23] ng/L; P <0.001). The strongest correlation between troponin values at corresponding times was before exercise ( r =0.92, P <0.0001). The strongest correlations at 3 hours were between the 2 races ( r =0.72, P <0.001) and at 24 hours between the cardiopulmonary exercise test and the second race ( r =0.83, P <0.001). Participants with the highest or lowest cTnI levels showed no differences in race performance or baseline echocardiographic parameters. Conclusions The variation in exercise‐induced cTnI elevation is largely determined by a unique individual cTnI response that is dependent on the duration of high‐intensity exercise and the timing of cTnI sampling. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02166216 .