Heart rate?

Question

Why do athletes have lower resting heart rates and couch potatoes have higher resting hr? a citation would be appreciated

Answer 1

Athlete's heart is a medical syndrome where an athlete's heart becomes enlarged from exercise, resulting in a lower resting pulse than that of an average person. These changes would indicate heart-disease if observed in a sedentary person, but in an athlete a large heart with a slow resting pulse is the result of normal and healthy physiological adaptions, and indicates a high level of fitness.

Answer 2

The most important muscle an athlete develops is her heart. Generally as she becomes more fit, her resting heart rate slows - a sign that her heart is pumping blood with greater efficiency. In the first six to 12 weeks of training, resting heart rate decreases by five to 10 percent.
See: www.sportsdoctor.com/articles/heart.htm