Atrial Fibrillation (AFib) normally presents signs and symptoms related to the malfunctioning of heart. As the heart beats fast and its rhythmic contractions are not regular, some symptoms start to appear. They vary from person to person, but the most common are chest pain and activity intolerance. You will feel the urge not to continue with any exercise because the heart is not capable of maintaining a normal rhythmic contraction to supply blood to the lungs and the entire body.