Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!gatech!ncar!ames!amdahl!uunet!mitel!scs!cognos!geovision!alastair
From: alastair@geovision.uucp (Alastair Mayer)
Newsgroups: sci.bio
Subject: Re: Fat Swimmers
Message-ID: <421@geovision.UUCP>
Date: 12 Oct 88 14:21:43 GMT
References: <78300004@p.cs.uiuc.edu>
Reply-To: alastair@geovision.UUCP (Alastair Mayer)
Organization: GeoVision Corp, Ottawa, Canada
Lines: 27

In article <78300004@p.cs.uiuc.edu> gillies@p.cs.uiuc.edu writes:
[...]
>I seem to remember reading a table that said world-class marathoners
>average 8.5% body fat, and swimmers average 12+% bodyfat.  Does
>someone know the REAL (i.e. researched/verified/published) answer to
>this question?

Several reasons.  Bouyancy has already been mentioned, but the assumption
made by other posters was that this is a benefit *despite increased drag*.
Actually, a small increase in fat *decreases* drag in water.  Air drag
for a runner and water drag on a swimmer are totally different - water
is much more viscous and incompressible, so you get better drag reduction
by "filling out" to a rounded shape rather than just minimizing cross
sectional area.
   Further, thermal considerations enter into it.  Heat generated by
exertion is shed much better by a swimmer to water than by a runner
to air.  A runner *must have* less body fat to help shed heat better,
a swimmer doesn't have this problem - indeed, has an opposite problem,
needing some fat to prevent too-fast heat loss from the muscles reducing
their efficiency.

  I don't know if any of this is researched/verified/published, just
seems common sense from fluid dynamics and thermodynamics standpoint.

 -- Alastair Mayer
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