How does being physically fit affect your resting heart rate?

Yes, it will take longer and more strenuous exercise for someone who is more fit to reach a maximum heart rate than it will for somebody who is not as physically fit. This is because in a physically fit person, the heart is more efficient: it pumps more blood with each heart beat. Usually, the heart of a physically fit person is also larger (which helps them pump more blood.) The blood of a physically fit person also contains more red blood cells, which carry oxygen to tissues in the body.