Ultra-marathon running has enjoyed increasing popularity, with the number of master ultra-marathon runners growing annually. This study presents a case of a 51-year-old highly experienced long-distance runner (body mass: 65.1 kg, body height: 168 cm), who took part in a 48-h ultra-marathon race held in 2010, but dropped out of the competition due to acute cardiac problems manifested after 16 h of running and having completed a distance of 129 km. Two weeks following the race, intense cardiac examination was performed to explain the drop-out due to chest pain. A 12‑lead electrocardiogram, a 2D transthoracic echocardiography in 3 apical projections of the left ventricle, a computed tomography of the chest, an invasive coronary angiography and a maximal oxygen uptake (VO_2max) test were performed. The 12-lead ECG revealed a negative T wave in III and aVF without morphological abnormalities. The echocardiographic examinations presented a normal size and function of the heart chambers, and a normal valvar structure and function (only trivial mitral and tricuspid regurgitation was observed). The invasive coronary arteriography – due to an increased calcium score in the CT scan – showed only a non-significant systolic dynamic narrowing in the eighth segment of the left anterior descending artery due to a muscle bridge. The physical performance characteristics of the athlete and a follow-up history of his athletic activity showed that the cardiac problems he had experienced during the ultra-marathon race did not prevent him from being active in sport. Int J Occup Med Environ Health. 2020;33(4):523–34