On Tue, 20 Mar 2001, Philip Thrift wrote:

> On Tue, 20 Mar 2001 07:20:26 -0500, Todd Moody <[log in to unmask]>
> wrote:
>
> It seems to me that racketball is like high-impact aerobics. I would
> think it's a pretty bad idea considering what it can do to your joints.

The question was, what evidence is there that it causes muscles
to shrink?  As for joints, I'm sure that there is an element of
risk involved, as there is for weight training.  An important
difference between racketball and forms of high-impact aerobics
is that in the latter, but not the former, the movements are
repetitive.  Racketball is a variable-intensity sort of exercise,
involving lots of different movements, but there may well be some
danger of tennis elbow or something of the sort.  This is
probably a good reason not to rely exclusively on racketball for
fat-burning exercise.

> Here is an interesting comment on this type of activity and muscle loss:
>
> http://www.nfpt.com/Library/Articles/badnews.html

The trouble with this article is that once again it considers the
goals of muscle *building* and fat-burning in opposition.  That's
not strictly relevant to my situation, since my muscle building
period appears to be over.

A useful passage from the article is this one:

        INTENSE aerobic sessions are your muscle's worst enemy.
        Consider this. Generally speaking, during intense aerobic
        activity, extramuscular fat is released into the blood
        and taken up by tissue cells at a specific rate and no
        more, dependent on several factors. This means, that
        whenever your level of exertion exceeds your "fat
        supply", the balance of energy will have to come from
        somewhere else. The body will resort to exhausting
        available blood glucose, liver glycogen, muscle glycogen,
        amino acids, and tissue will be cannibalized! All things
        considered then, if extramuscular fat loss is desired,
        why exercise at an intensity level higher than the
        optimal rate fat can be released? The aforementioned
        guidelines concerning low level activity should be your
        fat loss method of choice.

This is a good argument for using aerobic exercise at the lower
end of the intensity scale.  And in any case, for cardiovascular
conditioning (for those who believe in such a thing) there is
evidence that short intervals of higher-intensity aerobic
activity is sufficient (see http://www.ageless-athletes.com ).
There is also a "conditioning effect" from aerobic exercise that
increases the rate at which fat is used.  This seems to me to be
a desirable change to bring about: increased fat mobilization at
submaximal exertion levels.  Phinney's studies of the effects of
ketosis on trained endurance athletes also shows that
carbohydrate restriction increases fat utilization rates (after
an adaptation period).

>   The lower your metabolic rate, the less muscle tissue you will lose.
>   The higher your metabolic rate, the more muscle tissue you will lose.

Given my body temperatures, I suppose my metabolic rate is very
low indeed.  In any case, my concern is to enhance fat-burning,
and I understand that high-intensity aerobic exercise is not the
way to go for that.  Maybe racketball is too intense; I really
don't know.

> Is there a definitive scientific study "proving" any of this? Don't
> hold your breath. (actually deep breathing exercise may be a very
> useful aerobic excercise.)

Some people get very good results, it seems, with the Oxycise and
Body Flex breathing systems.  It's something to consider.

Todd Moody
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