Re: Running in marathons impairs immunity

In article <[EMAIL PROTECTED]>, John 'the Man' wrote:
   
> "Although moderate exercise may boost the immune system, research has
> shown that pushing the body's limits during an endurance activity like
> a marathon can temporarily weaken the immune system, Nieman told
> Reuters Health in an interview. Because of this, endurance athletes
> are at increased risk of illness following an event, according to
> Nieman. 

And do you have any idea how frequently a marathon specialist runs a 
marathon ? Do you think these guys could really give a flying f*** if they
catch a cold each year ? Did you consider the possibility that after the
event, the relative lack of activity (3 weeks rest is normal post-marathon)
reduces the risk of infection ? 

> The North Carolina researcher, a marathon runner himself, explained
> that when people exercise for 90 minutes or more without taking a
> break, carbohydrate stores in the body drop. The brain senses this
> decline and releases large amounts of stress hormones, Nieman said. 

How frequently do you think the typical runner trains for more than 90 minutes
in a single session ?

> The release of stress hormones leads to "huge changes" in the immune
> system, Nieman explained. This immune effect can last as little as 3
> to 6 hours or as long as 3 days, he said. 

And it's going to be closer to the 6 hours if the training session is an 
easy training run, which is much slower than race pace.

> These immune system changes help explain why endurance athletes are at
> increased risk of getting sick after a race, Nieman noted. 

Provided the race is in excess of 90 minute duration. But most endurance 
athletes rarely compete in such races.

> "By far, the most important finding that has emerged from exercise
> immunology studies is that positive immune changes take place during
> each bout of moderate physical activity. Over time, this translates to
> fewer days of sickness with the common cold and other upper
> respiratory tract infections. 

In other words, marathon runners are at greater risk of infection than 
others -- for a period of  "as long as 3 days" in a given year, or maybe
even 6 days if they race twice. For the rest of the year, they're better
off. Also, note that the real-world data -- the actual data on illness,
as opposed to theoretical illness caused by immune system changes -- supports
the case that the overall effect is beneficial, even if the actual race 
itself is not.

> This is consistent with public health
> guidelines urging individuals to engage in near-daily physical
> activity of 30 minutes or more. Risk of upper respiratory tract
> infections can increase when athletes push beyond normal limits. The

Yes, but athletes do not usually "push beyond normal limits" in training. It
is true that an overtrained athlete is likely to come down with a cold. That
is an argument for not overtraining. It is not an argument for not training
at all.

> When it comes to exercise, a lot of people like to take an extreme
> position.  Either they claim that they exercise because they do Hatha
> Yoga (ie, the extreme of deficiency), or they insist upon running in
> those 26 mile marathons (ie, the extreme of excess).  Marathon runners
> are really an insane group of people.

You're talking as if these runnerns go out and run a marathon every day.

> What is important here is that "positive immune changes take place
> during each bout of moderate physical activity. Over time, this
> translates to fewer days of sickness with the common cold and other
> upper respiratory tract infections."

Yes, that's why it's important to avoid escalating training too quickly.

> The immune system is what keeps people from coming down with cancer as
> we age.  And, it is moderate exercise that builds up your immune
> system; rather than being enticed into running a marathon and other
> extreme forms of exercise.

Again, no-one runs a marathon every day.

> "Many components of the immune system exhibit adverse change after
> prolonged, heavy exertion lasting longer than 90 minutes."  Thus, 90
> minutes should be the maximum length for all workworks, particularly
> for continuous exercise activities.

That sentence only supports 90 minutes for strenuous exercise. The marathon
runner performs their long runs (usually about 2hrs duration for an elite
runner) at an easy pace, so it is not "heavy exertion".

> By paying attention to your exercise intensity, such as with METs, it
> is better for your heart to cram more intensity into a shorter workout
> than to perform low-intensity activities over a longer duration.

This is not supported by that sentence. Increasing intensity makes the exertion
"heavier". It also results in rapid glycogen depletion, which *you* asserted
(or cited an article that you didn't understand which asserted) is the source
of the immune system problems induced by exercise.

Cheers,
-- 
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/