Heart rate monitor question?

[mdm]

Hi, I hope somebody can answer some questions. I'm looking for some heart rate monitors and I really got confused about the size of the watch and the chest belt. I'm wanting to find a watch and belt that will fit. When I look at the sites they don't say to much about the size of the watches. I'm needing a pretty big watch band, I think. Also, why is it so important to raise the heart rate higher during exercise? If I walk and go at a pretty decent pace is that enough? What does raising the heart rate do? Any help would be welcome.

 

[blindside]

raising the heart rate will make your heart work harder, so when you recover you'll make your heart (and cardiovascular system) more effiecient. Consequently meaning you'll go faster and harder with not as much effort.