Atrial fibrillation (AF) is an irregular and often very fast heart rhythm, is considered the most common sustained cardiac arrhythmia in adults worldwide, and its incidence and prevalence are increasing. Currently, the estimated prevalence of AF in adults is 2-4%, and is projected to increase 2.3-fold.

AF is associated with increased morbimortality and other comorbidities (hypertension diabetes etc.) which places a significant burden on the patient himself, social health and also on health and social care expenditure.

The European Society of Cardiology proposes an integrated ABC model (A: Anticoagulation, B: main symptom management, C: optimization of comorbidities and cardiovascular) and within this model, catheter ablation (B) is considered one of the main treatments to control AF symptoms; physical activity (C) is considered one of the modifiable health risk factors and is considered within a lifestyle intervention together with weight loss.

Catheter ablation of AF is currently the treatment of choice for paroxysmal AF. It uses small burns or frostbite to cause some scarring inside the heart to help interrupt the electrical signals that cause the irregular heartbeat. It is a safe procedure that has been shown to be more effective than treatment with antiarrhythmic drugs in reducing the arrhythmic burden and, therefore, the morbidity and mortality associated with the pathology.

Many studies have demonstrated the beneficial effects of moderate physical activity and physical exercise on cardiovascular health. However, there is still controversy as to whether physical activity is associated with an increased risk of AF in the general population; while some studies report a decreased risk of AF, others suggest an increase or that there is no evidence of an association between AF and physical activity.

Few studies have yet focused on the effects of physical activity in those subjects who have undergone catheter ablation. Studies that have evaluated physical activity with questionnaires associate it, when of moderate or high intensity, with lower recurrence of AF and lower incidence of serious events. It is true that the practice of regular and controlled physical exercise is a recognized part of the comprehensive care of patients with coronary heart disease (patients whose heart has difficulty receiving blood), and exercise is systematically identified as a central element of their rehabilitation. However, to date there is no similar approach for AF ablation patients.

Given the current situation of the subject of interest, the main objective of this project is to study the influence of a physical exercise program in patients undergoing catheter ablation of AF on different morphological and physiological variables of the heart, levels of physical activity and quality of life of patients. Investigators intend to recruit 120 participants, who will be randomly and equally distributed into a group that will perform a physical exercise intervention and a control group that will not perform any type of intervention. Participation in the study will not disrupt the normal practice of the health care system with these patients.

This is a randomized, controlled trial. The study will be conducted in collaboration with researchers from the GENUD (Growth Exercise NUtrition and Development) and BSICoS (Biomedical Signal Interpretation and Computational Simulation) research groups at the University of Zaragoza (Spain), and also with the Hospital Clínico Universitario Lozano Blesa, Zaragoza (Spain), specifically with the arrhythmia department of the cardiology service of that hospital.

The main objective of the study is to study the effect of physical exercise in people who have undergone atrial ablation at least one year ago on AF recurrence, heart morphology and function, level of physical activity, sleep quality, physical condition, quality of life, and hospitalization or adverse events. In addition, investigators also aim to assess gender differences in response to physical exercise after atrial ablation on the above-mentioned variables. Due to the characteristics of the project, insurance has been contracted to cover possible risks that may be contemplated during training and evaluations.

The first phase of the study corresponds to the recruitment of subjects and will be carried out among patients in the Arrhythmia Unit of the Hospital. All patients who have been undergoing catheter ablation as a medical treatment for AF for one year will be invited to participate and all those who wish to participate in the study must complete the informed consent form. Therefore, the incorporation of participants in the study will be periodic (weekly and/or monthly) and "drop-by-drop".

The subjects who will participate in the study will be patients, women and men, over 18 years of age, who underwent catheter ablation as medical treatment for AF and who currently have no recurrence of this arrhythmia. The inclusion and exclusion criteria are detailed in the corresponding section.

To calculate the sample size, a statistical power analysis was performed through the G*Power program with the following input parameters to obtain the effect of time: effect size (f = 0.25), type I error (α = 0.05), power level or type II error (0.95), number of measurements (3: pre-, post-ablation and follow-up). Our analysis revealed a total sample size of 54 individuals per group. Based on the previous years' care activity, the investigators expect to recruit at least 60 patients for each group (intervention and control) to guarantee the number of 54, considering a dropout around 10%.

All participants (both groups) will be evaluated at 3 points in time. The first evaluation will be at the time of recruitment, prior to the start of the physical exercise intervention (month 0), to determine the patient's initial condition. The second evaluation will take place after the end of the intervention (month 3), to study the effects of physical exercise and the last one 6 months after recruitment, to assess the detraining of the intervention group and continue with the follow-up of the control group.

All assessments will consist of two days of measurements. One day will include physical fitness, physical activity, body composition and quality of life questionnaires and the other day will include cardiac assessment by echocardiogram and electrocardiogram. Each of the measurements is mentioned below (the measures are described in the corresponding section):

• Body composition.
• Electrocardiogram (ECG).
• Echocardiogram.
• Objective physical activity.
• Sleep analysis.
• Muscle strength.
• Cardiorespiratory capacity.
• Quality of life.
• Assessment of atrial fibrillation load.

The experimental design of the project is a randomized controlled trial where subjects will be assigned to one of two groups randomly defined using the randomizer.org website, considering sex and age: (a) control group, which will receive usual medical care and (b) experimental group, which will carry out a training program described below.

The intervention group will carry out a concurrent training program for 12 weeks, designed based on the scientific evidence currently available and following the latest recommendations (year 2023) for the diagnosis and management of AF from the American College of Cardiology (ACC) and the American Heart Association (AHA). During the 12 weeks of training (3 months) the weekly frequency will be 3 days per week. The duration of the sessions will increase progressively from week 1 to week 4. The sessions consist of resistance and aerobic training, and are divided into warm-up, resistance training with free weights (8 exercises, 3 for the lower body and 5 for the upper body), aerobic training on a cycle ergometer and a cool-down with stretching. Aerobic training will increase in duration from week 1 (30 min/day) to week 5 (50 min/day), following the principle of training progression. The same will be done with resistance work, being carried out once a week during the first 4 weeks and twice a week from weeks 5 to 12, adjusting the workloads individually based on the patient's progression.

The intensity of the training will be moderate and always individualized, based on the theoretical maximum heart rate (HRmax) calculated with the equation of Gellish et al. [207-(0.7*age)] for aerobic work (64-74% FCmax) and in repetitions in reserve (RIR) for resistance work (4-6). Overall, the perceived sense of effort is intended to be around 3-4 on the modified Borg scale (0-10). To perform a subsequent analysis of adherence to the physical exercise program by these patients, an individual attendance record will be made at the training sessions.

Inclusion Criteria:

• Patients aged ≥18 years
• Undergoing catheter ablation as medical treatment for AF at least one year prior to enrollment.

Exclusion Criteria:

• Patients who do not sign the informed consent for participation in the study.
• Severe atrial dilatation.
• Structural heart disease.
• Pathology that prevents the normal practice of intervention with physical exercise