Atrial fibrillation (AF) is the most common arrhythmia in clinical practice, with an estimated prevalence of 0.4% to 1% in the general population, increasing with age to 8% in those above 80 years. The recognised risk factors for developing AF include age, structural heart disease, hypertension, diabetes mellitus or hyperthyroidism. However, the mechanisms underlying the initiation of AF in patients below 60 years of age, in whom no cardiovascular disease or any other known causal factor is present, remain to be clarified. This condition, termed as lone AF, may be responsible for as many as 30% of patients with paroxysmal AF seeking medical attention. Recent studies suggest that long-term endurance exercise may increase the incidence of AF and atrial flutter (AFl) in this population. This review article is intended to analyse the prevalence of AF and AFl, the pathophysiological mechanisms responsible for the association between endurance sport practice and AF or AFl and the recommended therapeutic options in endurance athletes.