Newsgroups: misc.fitness
Date: Sun, 27 Sep 1992 16:54:36 -0400 
From: Kimberly Sewright <ks57+@andrew.cmu.edu>
Subject: Re: Aerobic Heart Rate Question

Excerpts from netnews.misc.fitness: 26-Sep-92 Aerobic Heart Rate
Question by Steve Russell@wam.umd.ed 
>    I think I've been pushing myself too hard in my aerobic workouts because
> it seems like I havent been losing fat and until I slowed down my endurance
> as well as my post workout recovery were getting worse.  I feel better and
> am getting more endurance now that Im going slower.  However, I dont want to
> exercise forever.  Id like to go as high as I can and still get aerobic
> benefits.  Would anyone know if I could just count my pulse on my own taking
> the standard deviation I mentioned in the last paragraph into account or
> would exercising change the gap between my "real" and "manually measured"
> pulse rates?


Always remember that the only way we know what our maximum heart-rate or
our maximum oxygen intake is, is to be tested in a lab. There is a
linear relationship between the two. When our oxygen intake goes up so
does our heart-rate. 

Why is this important? If our need for oxygen to work aerobically
(production of ATP with oxygen) is exceeded, then we begin to work
anaerobically (production of ATP without oxygen). To burn fatty-acids
oxygen is needed. We can't measure our oxygen intake in an aerobics
class, but since there is a linear relationship between oxygen intake
and heart-rate, we can monitor our oxygen intake by taking our pulse. 
Through research it has been found that we begin to work anaerobically
at around 85% of our maximum heart-rate. 

To find your approximate maximum heart rate use this formula:
(220 - your age).

You want to make sure your pulse does not exceed 85% of this number.  As
far as burning more fat by keeping your intensity down.  It is not at
all surprising that you have experienced a correlation.  When working
aerobically, it takes at least ten minutes before your body begins to
burn fatty acid instead of carbohydrates. The difference in the amount
of ATP produced is around 36 units for carbos and 100 units for fatty
acids. So the longer you can keep up your aerobic activity, the more fat
you burn.

In the past few years the industry has been promoting a new way of
monitoring heart-rate.  It is called "Perceived exertion". It argues
that we shouldn't be so preoccupied with the exact numbers since
everyone IS different. Instead ask yourself (and be honest) Am I working
1) not at all 2) a little 3) moderately 4) somewhat hard  5)hard  6)very
hard 7)extremely hard.  As long as you are working "somewhat hard" to
"hard" you should be between 65% and 75% of your maximum heart-rate. or
as they say "in your target zone"

There is also the "talk test". If you can talk to the person next to you
without gasping for air, great! If you can carry on a lengthy
conversation, then you aren't working hard enough! 

Just remember, the most important thing is DURATION! The longer the
better! But if your heart-rate is at least at 55% of maximum than it
doesn't matter how long you do it, you aren't doing much! 

I hope this answers some questions
Good luck,
Kim Sewright