i normally do about 5 on the elliptical, just enough to get loose and get the target heart rate.
If you're just looking to get loose before lifting, that's fine, but it's not doing your heart any good. Have to keep the heart rate up for 20 minutes to exercise heart muscle.
More muscle is still more weight, and that's going to put stress on your heart.
"What really bugs me is that my mom had the audacity to call Flash Kit a bunch of 'inept jack-asses'." - sk8Krog
...and now I have tape all over my face.