Atrial fibrillation (AF) is the most frequent arrhythmia occurring in 0.1% - 4.0% of the population and the prevalence increased to 7.2% in patients aged ≥ 65, with an annual increase of 1.6% in patients aged ≥ 75. Characterized by loss of atrial contraction capacity (loss of atrial systole), AF is responsible for almost one-third of hospitalizations for heart rhythm disturbances. It may present high morbidity and mortality due to hemodynamic involvement, cardiomyopathy due to tachycardia and thromboembolic phenomena.

Risk factors for the development of AF include cardiac and non-cardiac factors such as age, structural heart disease, hypertension, diabetes mellitus and hyperthyroidism.1 The change in cardiac function is associated with increased mortality and risk of infarction, decreased quality of life, decreased exercise capacity and impaired left ventricular function.2

It is known that physical activity is an effective adjunct in the treatment of various types of cardiovascular diseases. However, patients with AF present decreased tolerance to exercise, dyspnea and palpitations.3 Some studies report a J or U curve between the correlation of intensity of physical activity and AF.4^-10 On the other hand, some studies show a linear correlation between the amount of physical activity and the development of AF.11^-14

Considering the regular practice of physical activity as a cardiovascular benefit and literature inconsistency about its potential arrhythmogenic effect, the objective of this study was to analyze the effects of physical activity on the incidence of AF.

Search on the chosen databases resulted in 731 articles. After reviewing the titles, abstracts and articles repeated, a total of 11 studies were included in this systematic review.

Although the benefits of physical exercise on cardiovascular diseases are well described, the same does not occur in relation to AF. In this sense, the results of this meta-analysis, based on the studies analyzed, indicate that individuals who exercise are less likely to have AF.

Mozaffarian et al.,10 suggest that mild and moderate activities, especially leisure activities such as walking, are associated with a significantly lower incidence of AF. On the other hand, Drca et al.,15 observed an increased risk of the development of AF in men under 30 years of age submitted to high levels of exercise, and this does not occur at older ages. In this sense, Larsson et al.,16 suggest that maintaining a body mass index (BMI) of less than 25 kg/m², doing more than 20 minutes of exercise daily, not consuming or consuming alcohol in a mild to moderate manner (≤ 2 drinks/day for men and ≤ 1 drink/day for women) and not smoking reduce the risk of developing AF by half.

Bapat et al.,6 from the Multiethnic Atherosclerosis Study (MESA), associated physical activity and AF in a diverse population without clinically recognized cardiovascular disease. The results showed that neither vigorous physical activity nor total intentional exercise were independently related to AF, when adjusted for some covariates. It has even been shown that the greater the relationship of the individual with vigorous activities, the lower the risk of AF. Also, Ofman et al.,17 after meta-analysis involving 95,526 individuals, did not identify a statistically significant association between regular physical activity and increased incidence of AF. In this sense, the guidelines recommend performing at least 150 minutes of moderate physical activity or 75 minutes of intense physical activity per week.18

Patients with AF report symptoms such as decreased exercise tolerance, dyspnea, palpitations and fatigue, which directly affect the quality of life. However, physical exercise and training decrease these symptoms, and may have antiarrhythmic effects in individuals with paroxysmal AF, as well as protect against the development of AF.19 In this sense, in order to verify the effects of training on the functional capacity of individuals with AF, Luo et al.,20 submitted patients with AF and patients after myocardial infarction with reduced ejection fraction to supervised training with aerobic exercises, three times a week for 36 sessions, then moving on to a home program for another two years. The training was efficient, resulting in increased cardiorespiratory capacity and peak VO₂ in both groups, but no significant differences were identified between the groups.

The international guidelines recommend the practice of physical activity in patients with AF in order to reduce their comorbidities.21 When Malmo et al.,22 submitted 26 AF patients to interval aerobic training, demonstrated that 12 weeks were enough to decrease arrhythmic load, besides causing a decrease in the symptoms related to AF. In addition, improvement in maximum work capacity, atrial and left ventricular function, lipid levels and quality of life were identified. For Osbak et al.,3 patients with heart disease lose muscle mass and strength due to inactivity and local hemodynamic changes. This way, developing strategies that allow the increase of muscle strength in these patients becomes important in order to increase mobility, posture and balance.

In an observational study of 20,000 adults, Proietti et al.23 observed lower all-cause mortality in AF patients who reported being involved with regular physical activity. Still, Hegbom et al.,24 and Plisiene et al.,25 demonstrated improvements promoted by physical exercise in quality of life, in addition to the reduction of symptoms in patients with AF.

According to Anderson and Taylor,26 physical capacity is the main clinical outcome of cardiac rehabilitation, regardless of diagnosis. For each increase of 1 Metabolic Equivalent (MET) in physical capacity, mortality rate decreases by 17% in men and 14% in women. Thus, physical exercise seems safe for patients with AF besides triggering several benefits.27

Another important factor is the strong relationship between obesity and AF. According to Pathak et al.,28 electrical factors and structural remodeling caused by obesity lead to the genesis and perpetuation of AF. In this sense, physical exercise, in addition to assisting in weight loss and consequent reduction in AF recurrence,5^,29 may protect against AF even in the presence of obesity.30

The study by Pathack et al.,31 showed that an increase in cardiorespiratory fitness around 2 METs was associated with reduced density of AF. According to Abed et al.,32 decrease in AF density due to exercise can be explained by increased cardiorespiratory capacity and weight loss. Increase in each metabolic equivalent (MET) results in a 20% decrease in the risk of recurrence of AF.32 Skielboe et al.,33 in order to verify if high-intensity exercises were more effective in decreasing AF density than low-intensity exercises, did not identify differences. However, it has been shown that high-intensity exercises do not increase risk and that patients tolerate exercises of this type.

Regular practice of physical activity has been reported to increase vagal tonus due to physiological adaptations resulting from increased cardiac work,34 inducing electrical stability of the heart and maintenance of homeostasis. In this sense, low resting HR tends to represent a good health picture.35 Thus, well-trained or physically conditioned individuals have lower resting HR, which suggests greater parasympathetic activity36 or less sympathetic activity.37 Still, Uusitalo et al.,38 and Bonaduce et al.,39 doing studies with longitudinal characteristics, observed a reduction in resting HR, although significant abnormalities in the autonomic indicators were not identified. Thus, Catai et al.,40 suggest that exercise-induced bradycardia may result from intrinsic sinus node adaptations.

Like any systematic review, this study also presents limitations, since the results demonstrated here are limited by the quality of the studies available. This way, trying to make a complete literature review, all studies available, on the proposed theme, were included, and were evaluated, however, with a robust quality meta-analysis technique. In addition, the data analyzed were not stratified by type of exertion, gender or age.

It is concluded, therefore, that physical exercise, lato sensu, without stratification by intensity, sex or age, does not seem to be associated with an increase in the occurrence of atrial fibrillation.