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Why is a TOO big heart bad ?

Tracy Aquilla aquilla at salus.med.uvm.edu
Thu Oct 13 16:29:01 EST 1994

In Article <37jmf3$r0l at news.bu.edu>, kondo at buphy.bu.edu (Richard Kondo) wrote:
>Lombard FranCois (lombardf at uni2a.unige.ch) wrote:
>: A student of mine (I teach Biology to 15-18 year olds) asked why it isn't
>: so good to develop a too big heart (very intense training of teenagers is
>: supposed to be bad for that reason , amongst others)
>: Any help, or suggestion as to where I should post this are welcome.
>: FranCois Lombard
>: lombardf at uni2a.unige.ch
>        Developing a larger heart is known as cardiac hypertrophy. 
>Hypertrophy occurs in athletes and in persons with hypertension;
>however, the type of hypertrophy differs.  Generally, aerobic exercise
>such as running leads to increased size of the heart, but not increased
>mass.  On the other hand, hypertension leads to increased mass.  The first
>type of hypertrophy (that developed by athletes) is beneficial, while the
>hypertrophy associated with increased blood pressure is deleterious.  The
>exercise physiologist in our lab says that aerobic exercise has always
>been shown to be good(for the heart).  The one possibility is  that 
>weight training leads to
>hypertrophy more similar to that in hypertension, according to him.
>Richard Kondo
>kondo at buphy.bu.edu
>Cardiac Muscle Research Lab
>Boston University, Boston

How can the heart grow larger without getting heavier? I don't believe that
the athletic heart can grow significantly in size without also gaining mass;
how would this be possible? There are many ways one can develop cardiac
hypertrophy, hypertension is just one of the most common ways, but there are
also genetic disorders, viruses, etc., which can cause cardiac hypertrophy.
It is my understanding that the significant physiological differences
between athletic cardiac hypertrophy and 'disease' hypertrophy are not very
well understood. This is probably why Francois heard that it is not good to
train young athletes too hard; it isn't certain that this won't be
detrimental to their health in the future. However, hypertrophied hearts in
a diseased state tend to relax more slowly after contraction (slower
recovery), and develop less power, whereas the athletic heart is capable of
performing normally. Also, I think that weight training will result in an
athletic heart, similar to that developed from aerobic exercise; I have seen
no evidence to the contrary.

Tracy Aquilla, Ph.D.
Molecular Physiology and Biophysics
University of Vermont
aquilla at salus.med.uvm.edu

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