The heart is vital in supplying all cells throughout the body with oxygen and nutrients. Bradycardia means slow heart rate. It can slow down for many reasons, and in itself is not a problem if it is compensated for by a larger stroke volume, or amount of blood pumped each beat. Many athletes have slow resting heart rates, and this is a sign of good heart health. Bradycardia typically does not cause symptoms until the rate drops below 40 bpm. When symptomatic, it may cause fatigue, weakness, dizziness, sweating, and fainting.