My patient wants to perform strenuous endurance exercise. What's the right advice?

•Running marathons has recently been associated with potential deleterious cardiac effects.•This topic is medically important due to the increasing number of participants.•We provide a summary of the evidence available on strenuous endurance exercise.•This type of information can help physicians give advice to their patients and the general public.

Prolonged strenuous endurance exercise (SEE) such as marathon running has recently been associated with potential deleterious cardiac effects, particularly increased risk of atrial fibrillation (AF). This topic is medically important due to the increasing number of participants in SEE events lasting several hours, including older people. The aim of this narrative review is to provide a summary of the evidence available on SEE and related issues such as cardiovascular mortality, AF, potential cardiac remodeling, cardiovascular events during exertion, or the need for pre-participation screening (with a special focus on beginners). This type of information can help physicians giving advice to their patients and the general public regarding safe SEE practice.