Figure 3. Percentage (95% CI) of participants with lone AF (cases) according to accumulated high-intensity physical exercise (local likelihood regression). Of note, proportion is dependent on cases/control matching in a specific study sample. When considered as a continuous variable, the relationship of lifetime-accumulated high-intensity training to AF risk followed a U-shaped dose–response curve. Reprinted with permission from Calvo N, Ramos P, Montserrat S, et al. Emerging risk factors and the dose-response relationship between physical activity and lone atrial fibrillation: a prospective case-control study.