The positive effects of physical activity are countless, not only on the cardiovascular
system but on health in general. However, some studies suggest a U-shape relationship
between exercise volume and effects on the cardiovascular system. On the basis of
this perspective, moderate-dose exercise would be beneficial compared to a sedentary
lifestyle, while very high-dose physical activity would paradoxically be detrimental.
We reviewed the available evidence on the potential adverse effects of very intense,
prolonged exercise on the cardiovascular system, both acute and chronic, in healthy
athletes without pre-existing cardiovascular conditions. We found that endurance sports
activities may cause reversible electrocardiographic changes, ventricular dysfunction,
and troponin elevation with complete recovery within a few days. The theory that repeated
bouts of acute stress on the heart may lead to chronic myocardial damage remains to
be demonstrated. However, male veteran athletes with a long sports career show an
increased prevalence of cardiovascular abnormalities such as electrical conduction
delay, atrial fibrillation, myocardial fibrosis, and coronary calcifications compared
to non-athletes. It must be underlined that the cause–effect relationship between
such abnormalities and the exercise and, most importantly, the prognostic relevance
of such findings remains to be established.
