KB,

Actually there is some research out there on heart rate and aerobics,
linking too much ticking to early wear-out of your ticker.  The super slow
site has an article on "Atrial Fibrillation and Exercise"  aka heart attacks
from aerobics. They have lots of good articles against aerobics:

http://www.superslow.com/main.html


Thing is, there is 0 correlation between VO2 max and aerobic energy--that's
where aerobics loses out over strenght training, which has clear positive
correlations..  There is a study--I can't remember where, but its out there
if you look hard enough, where they had the subjects ride a bike using only
one leg or something.  Their VO2 max increased with this.  After  however
many weeks, they retested, and yes the VO2 max had increased significantly
over when they started, when they rode with that leg.  But not when they
rode with the other leg.
The conclusion is that VO2 is musculature in nature--and has nothing to do
with heart strengthening by making it beat more through aerobic exercise!

Most people do aerobic stuff to try to lose weight.  Funny, because sittin
at my computer burns only 50 calories less an hour than taking a jog for an
hour.  And I dont need to lose weight.  And people who do are at particular
risk from injury involved in aerobics anyways, so they definitely shouldnt
do it.  I could drink a gallon of cold water a day and burn a hundred odd
calories, and sit around in t-shirts in my no central heating, and burn
more.  In fact I would rather do this than pound on my knees and lumbar and
swimmers shoulder.  I am finally getting them under control now.

You are right that the grinding and pounding on joints will make anyone give
up aerobics, but the problems from heart stuff is also a good reason to keep
away.

Judith