 [ Symptoms ] why would a 13 yr old athletic male have a slow heart rate [ Disease ] there may be two reasons one reason would be that he is in great shape runners tend to have slower heart rates 50 60 bpm so if he is a runner in good shape this could account for a slower and stronger heart rate unfortunately another reason could be a hidden cardiac problem i do not know how slow his heart rate is or if his heart rate is regular skipping beats etc so it would be wise for him to have a sports clearance by his medical provider or even a cardiologist this would be for your son is own protection