Trained athletes usually have lower resting heart rates than normal (for example, 50 beat/min in an athlete compared to 70 beats/min in a sedentary individual). considering that the resting co is 5000 ml/min in both trained athletes and sedentary people, what is responsible for the bradycardia of trained athletes?

Karen is waiting by the lockers before school for her friend richard. they had agreed to look over the history review sheet together to be ready for the test later that day. richard shows up late with uncombed hair and wrinkled clothes. karen: "you're five minutes late and you look like a wreck! " richard: (slams his locker) "you know, i don't have time for this." karen: "fine! figure out the test on your own! "