From: mazur@inmet.camb.inmet.com (Beth Mazur)
Subject: Re: Fitness thoughts
Organization: Intermetrics Inc, Cambridge MA
Date: Wed, 2 Sep 1992 15:11:00 GMT

In article <1992Sep1.185619.21142@mcnc.org> ekp@mcnc.org (Edward Pavelchek) writes:
>In article <1992Aug31.223257.2937@stortek.com> pae@blackcat.stortek.com (Phil Earnhardt) writes:
>>It may be about time to drop this discussion into email...
>
>Au contraire.  An earnest discussion of exercise metabolism must be
>worth at least 3 average jokes about Adam's legs.

I'll second that! (No offense to Adam.) 

>>Ed, are you disagreeing with the overall thesis -- that unfit people getting
>>fit should generally stay below the anerobic threshold? In other words, are
>>you saying that my thesis is flawed or that my reasoning is incorrect?
>
>No, I've repeated time and time again - it's hard to sustain anaerobic
>work, which limits you to too little exercise to really help.  For lots
>of the reasons we should be discussing.  On the other hand, some unfit
>person who jogs for 2 minutes, then walks until he can jog again, will
>probably get as much or more out of 3 miles as someone who just
>walks, even though he is above the lactate threshold.  It takes a lot
>more willpower, that's all.

Again, depends on whether one is trying to "get fit" or "lose weight."
Someone who is trying to get fit would do well to do as Ed suggests--
which is basically interval training.

However, the more glucose/glycogen that is used, the more that needs to
be replaced.  People who are trying to lose a substantial amount of
weight are proabably better off at a lower intensity (using a higher
percentage of fat as fuel), because the last thing they probably want 
are serious carbo cravings after exercise.

Anyways, much of this discussion has been my fault for badly paraphrasing
Covert Bailey regarding fat burning and anaerobic exercise.  Here's what
he and Martin Katahn (T-Factor) have to say:

From T-Factor (p. 208):

	"Start-stop activities [anaerobic - ed.] are carbohydrate-burning
	activities.  In general, they will burn between 60 and 70 percent
	carbohydrate and 30-40 percent fat in the fuel mixture.

	Continuous whole-body movements are fat-burning activities.  They
	will burn between 50 and 60 percent fat in the fuel mixture and
	40 to 50 percent carbohydrate."

From Fit or Fat (p. 55-57):  [ this one's for Ed, Harry, and Phil :-) ]

	"It's important that you realize the significance of the enzymes
	involved.  Literally hundreds of these ... are needed in each
	cell, and each one is quite different from each other...The only
	way enzymes increase in a muscle is when DNA ... makes more...This
	process is called enzyme biosynthesis and it takes place only if
	you eat adequately, if your cells aren't sick, and if you 
	exercise to stimulate the DNA to go to work.

	...The burning of glucose takes place in two stages.  During the
	first...glucose is broken down into pyruvic acid.  In the second,
	the pyruvic acid is completely disassembled into water and
	carbon dioxide...The enzymes used during the first stage need 
	very little oxygen to do their work...The enzymes that function
	during the second stage need lots of oxygen...

	...[A heart rate between 65-80% is] able to supply enough oxygen
	to the muscles so that glucose is disassembled through both
	stages and completely burned.  [If > than 80%, ] the heart
	and lungs cannot keep up with the oxygen demand in the muscle.
	When this happens, the glucose will only break down to pyruvic
	acid; there will not be enough oxygen to continue through the
	second stage.  Since pyruvic acid cannot be burned ... it 
	accumulates in the muscle and is converted into lactic acid...
	When you stop and "catch your breath", oxygen flows into the
	deprived muscle.  Most of the lactic acid turns back into
	pyruvic acid.

	...Unlike glucose burning, ... all the enzymes used in fat
	breakdown need a lot of oxygen.  Anaerobic exercise, therefore,
	effectively shuts off all fat burning and forces the muscles to
	use glucose exclusively."

Excuse the editing, but that's a lot of text--so I cut out what seemed
too verbose.  Anyways, exercise physiology is not my strong suit, so I
will let Ed have at this one :-).

Beth Mazur                   "...life is more than a vision.  The sweetest
mazur@inmet.inmet.com         part is acting after making a decision."
...!uunet!inmet!mazur                                  -- The Indigo Girls
Newsgroups: misc.fitness,rec.running