Inclusion Criteria:  Signed informed consent Age ≥ 18 years Diagnosed with paroxysmal AF Report >5 (running, rowing) or >8 (cycling, cross-country skiing), weekly hours, respectively, of endurance sport Use a training watch and a smartphone  Exclusion Criteria:  Permanent AF Cardiac conditions (including valve diseases, anomalies, coronary heart disease) Ejection fraction <45% Hypertension (>140/90) Diabetes mellitus Hyperthyroidism Smoking the 5 last years Alcohol abuse Use of illegal or performance enhancing drugs Body mass index >30kg/m2 Injuries preventing physical exercise Pregnancy Participation in conflicting intervention research studies Planned AF ablation within the next six months