Exercise >>> Mortality ... Was Re: Exercise >>> Immunity

[Guest guest]

Hi folks:

I wasn't able to access the comments linked in Al's post below. But

I wonder if they may refer in some way to a couple of 'issues' I have

with any study that relates exercise capacity to mortality or other

measures of health. In case they do not cover these issues, here

they are:

First, I have long been cautious about accepting at face value the

findings of the people at the Aerobics organization because

they have such a conflict of interest when it comes to anything to do

with exercise. A large proportion of their revenue stream depends

upon the sale of books, videos, lectures, equipment, consulting

advice, etc. advocating the benefits of aerobic exercise. If one

believed everything one hears them say one might think that exercise

cured everything. We discussed some months ago one study they did

which indicated, IIRC, that it was fine to be obese (yes, obese) so

long as you exercised a lot ............. [or at least bought books

or videos from them about it ;; ^ ))) ..... just joking about this

part in square brackets].

Second, there is the issue of chickens and eggs. A) In many of

these studies they examine the exercise capacity and subsequent

mortality OF PEOPLE WHO ARE REFERRED FOR TREADMILL TESTING. Now it

might be relevant to ask why they were referred in the first place.

Usually this is done because there seems to be a good reason

(symptom) to get checked out. Some of these people will have fairly

advanced heart disease (Clinton's arteries were reportedly 90%

blocked before he suffered symptoms that suggested a visit to his

GP); some will have much less advanced disease; some will have sub-

clinical disease; and others perhaps none at all. Clearly those with

the most advanced disease are likely to perform much less well on a

treadmill than those whose disease is much less advanced. So

naturally, those whose arteries are the most clogged will not only

perform the worst on the treadmill they will also die soonest. But

is these cases the exercise capacity is THE RESULT of the degree of

disease. The disease is not a reflection, in a causal sense, of how

fit they are.

Even in the case where the subjects chosen are symptom-free of

CVD, there will be varying degrees of CVD among the subjects since we

know that atherosclerotic lesions start to build up at a very early

age in a substantial proportion of the population, and grow at

different rates in different individuals. Again, those with the most

advanced disease will die the soonest, and the degree of disease will

be reflected in their 'fitness' however that is measured.

The above does not prove that exercise is not beneficial. Heck, I

have exercised a lot over the years because I hope it is helpful, and

still do when it is 'convenient'. My point is that these studies do

not prove exercise IS beneficial wrt mortality. Caution is advised,

imo, before drawing conclusions about which is the cause and which

the effect. I am sure there are ways to show definitively how big

the mortality benefit is from exercise. My bet is that when those

studies are done (perhaps they already have been, if so please post

them) the benefit, if any, for extending lifespan for people on CR,

will be rather marginal. But I will be happy to be persuaded

otherwise, by persuasive evidence.

The above said it does seem to me that we need to do the forms of

exercise that best preserve our performance with the least

expenditure of calories, so that we remain physically capable in old

age. The recent McMaster 'Wingate Tests' training approach seems to

me to have several benefits. When I have more experience with it I

will be posting my thoughts here in case anyone is interested.

Rodney.

> > " Each 1-MET increase in exercise capacity conferred a 12 percent

> improvement in survival. "

> >

> >

> >

> > NEJM

> >

> > Volume 346:793-801 March 14, 2002 Number 11

> >

> >

> > Exercise Capacity and Mortality among Men Referred for Exercise

> Testing

> >

> > Myers, Ph.D., Manish Prakash, M.D., Victor Froelicher,

> M.D., Dat Do, M.D., Sara Partington, B.Sc., and J. Edwin Atwood,

M.D.

> >

> >

> > ABSTRACT

> >

> > Background Exercise capacity is known to be an important

prognostic

> factor in patients with cardiovascular disease, but it is uncertain

> whether it predicts mortality equally well among healthy persons.

> There is also uncertainty regarding the predictive power of

exercise

> capacity relative to other clinical and exercise-test variables.

> >

> > Methods We studied a total of 6213 consecutive men referred for

> treadmill exercise testing for clinical reasons during a mean (±SD)

> of 6.2±3.7 years of follow-up. Subjects were classified into two

> groups: 3679 had an abnormal exercise-test result or a history of

> cardiovascular disease, or both, and 2534 had a normal exercise-

test

> result and no history of cardiovascular disease. Overall mortality

> was the end point.

> >

> > Results There were a total of 1256 deaths during the follow-up

> period, resulting in an average annual mortality of 2.6 percent.

Men

> who died were older than those who survived and had a lower maximal

> heart rate, lower maximal systolic and diastolic blood pressure,

and

> lower exercise capacity. After adjustment for age, the peak

exercise

> capacity measured in metabolic equivalents (MET) was the strongest

> predictor of the risk of death among both normal subjects and those

> with cardiovascular disease. Absolute peak exercise capacity was a

> stronger predictor of the risk of death than the percentage of the

> age-predicted value achieved, and there was no interaction between

> the use or nonuse of beta-blockade and the predictive power of

> exercise capacity. Each 1-MET increase in exercise capacity

conferred

> a 12 percent improvement in survival.

> >

> > Conclusions Exercise capacity is a more powerful predictor of

> mortality among men than other established risk factors for

> cardiovascular disease.