Background:Recent cross-sectional studies have suggested a dose-dependent relationship between lifelong exposure to physical activity and the burden of calcified coronary artery disease (CAD). No longitudinal studies have addressed this concern. Hypothesis: Exercise volume is associated with progression of coronary artery calcium (CAC), defined as ≥10 units increase in CAC score. Methods: Sixty-one recreational athletes who were assessed by coronary computed tomography angiography (CCTA) as part of the NEEDED 2013/14 study were reassessed 4-5 years later, in 2018. Results: Subjects were 45.9 ± 9.6 years old at inclusion, and 46 (74%) were male.Between 2013 and 2018, the participants reported median 5 (range: 0-20, 25th-75th percentile: 4-6) hours of high-intensity exercise per week. None of the included subjects smoked during follow-up. At inclusion, 21 (33%) participants had coronary artery calcifications. On follow-up CCTA in 2018, 15 (25%) subjects had progressive coronary calcification (≥10 Agatston units increase in CAC). These subjects were older (53 ± 9 vs 44 ± 9 years old, P = .002) and had higher levels of low-density lipoprotein