Exercise-induced release of cardiac troponin is attenuated with repeated bouts of exercise: impact of cardiovascular disease and risk factors

Abstract

Background: Prolonged exercise can induce cardiac troponin release. Since single bouts of exercise may protect against cardiac injury, we explored the hypothesis that the magnitude of exercise-induced release of troponin attenuates upon successive days of exercise. We also examined whether effects of successive exercise bouts differ between healthy participants and individuals with cardiovascular risk factors (CVRF) and established cardiovascular disease (CVD). Methods: We examined cardiac troponin I (cTnI) concentrations in 383 participants (61±14 years) at rest and immediately following 4 consecutive days of long-distance walking (30-50 km/day). Participants were classified as either healthy (n=222), CVRF (n=75) or CVD (n=86). Results: Baseline cTnI concentrations were significantly higher in CVD and CVRF participants compared to healthy (P<0.001). Exercise-induced elevations in cTnI were observed in all groups following all days of walking compared to baseline (P<0.001). Tobit regression analysis on absolute cTnI concentrations revealed a significant day*group interaction (P=0.04). Following day 1 of walking, post-hoc analysis showed that exercise-induced elevations in cTnI attenuated on subsequent days in healthy and CVRF, but not in CVD. Odds ratios for incident cTnI concentrations above the upper reference limit were significantly higher in comparison to baseline on Day 1 for healthy (4.90 (95% CI 1.58-15.2)) and CVD participants (14.9 (1.86-125)); and remained significantly higher than baseline on all subsequent days in CVD. Conclusions: The magnitude of post-exercise cTnI concentrations following prolonged walking exercise significantly declines upon repeated days of exercise in healthy individuals and those with CVRF, whilst this decline is not present in CVD patients.