On Wed, 31 Jul 2002, tsayonah wrote:

> Heard this on the morning news:  They said that cortisol is
> higher in the morning, exercise raises cortisol; therefore
> exercising in the morning gives a double boost.  They claim
> that cortisol suppresses the immune system.  Don't have this
> concept at my fingertips so was gonna look it up when I had
> time.  Anyone?

Cortisol does suppress the immune system, but as far as I know
the effect is caused by *chronic* elevated cortisol levels.
Cortisol is also one of the hormones involved in triggering
gluconeogenesis, which is *why* it's elevated in the morning,
since the nervous system has been using glycogen all night.  This
is also why exercise, especially intense exercise, raises
cortisol: glucose is needed for those fast-twitch fibers.

Cortisol is called a "stress hormone" because it is involved in
producing the fight-or-flight response, i.e., it prepares the
body for extreme exertion of short duration.  For that kind of
exertion we absolutely need glucose, so the cortisol steps up
production and release of it.  There should be a concomitant rise
in blood glucose, soon to be used during the fighting or fleeing.

When we trigger the fight-or-flight response and then do nothing,
we end up with elevated blood glucose and an over-aroused
sympathetic nervous system, and this bad news.  It's one of the
reasons why stress is such a killer.  It's really not the stress
that kills; it's the "civilized" refraining from fighting or
fleeing.

Bottom line: In my view, there's nothing wrong with pushing
cortisol up in the morning if you then do what we are supposed to
do: exercise briefly and intensely.

Todd Moody
[log in to unmask]