Although prevailing research trends favour large clinical trials and registries, meticulous observation during daily clinical practice remains a valuable source for hypothesis generation in medical research. Clinical experience has allowed the identification of several risk factors in the cardiovascular field. For instance, two groups of investigators noticed in parallel that patients with atrial fibrillation (AF) but no cardiovascular disease used to be healthy, fit, heavily trained middle-aged men. By the end of the 1990s and beginning of the 2000s, a series of articles were published confirming their observations: a history of continued endurance training associated with an increased risk of AF. Initial small case–control and cohort studies almost exclusively included men to accurately and homogeneously fit their observations and hypothesis, with women representing only 2% of all patients (figure 1). The link between physical activity and AF remained suspicious of bias and was largely disputed in the scientific community until the publication of large epidemiological studies. Similar to previous small studies, these were initially carried out in men; women were progressively included in subsequent works (figure 1). Finally, as evidence of this association had already been firmly established in men, an increasing need to test its validity in women aroused. Two studies exclusively focusing in women recalled initial clinical observations:1 ,2 women were not seemingly affected by the AF risks of exercise.