Sunday, August 29, 2010

Heavy physical activity may significantly reduce heart disease deaths, especially after age 45

The idea that heavy physical activity is a main trigger of heart attacks is widespread. Often endurance running and cardio-type activities are singled out. Some people refer to this as “death by running”. Others think that strength training has a higher lethal potential. We know based on the Oregon Sudden Unexpected Death Study that this is a myth.

Here is some evidence that heavy physical activity in fact has a significant protective effect. The graph below, from Brooks et al. (2005) shows the number of deaths from coronary heart disease, organized by age group, in longshoremen (dock workers). The shaded bars represent those whose level of activity at work was considered heavy. The unshaded bars represent those whose level of activity at work was considered moderate or light (essentially below the “heavy” level).


The data is based on an old and classic study of 6351 men, aged 35 to 74 years, who were followed either for 22 years, or to death, or to the age of 75. It shows a significant protective effect of heavy activity, especially after age 45. The numbers atop the unshaded bars reflect the relative risk of death from coronary heart disease in each age group. For example, in the age group 65-74, the risk among those not in the heavy activity group is 110 percent higher (2.1 times higher) than in the heavy activity group.

It should be noted that this is a cumulative effect, of years of heavy activity. Based on the description of the types of activities performed, and the calories spent, I estimate that the heavy activity group performed the equivalent of a few hours of strength training per week, plus a lot of walking and other light physical activities. The authors of the study concluded that “… repeated bursts of high energy output established a plateau of protection against coronary mortality.

Heavy physical activity may not make you lose much weight, but has the potential to make you live longer.

Reference:

Brooks, G.A., Fahey, T.D., & Baldwin, K.M. (2005). Exercise physiology: Human bioenergetics and its applications. Boston, MA: McGraw-Hill.

7 comments:

Michael said...

I would have to dig it up, but IIRC Fred "Dr. Squat" Hatfield commented on some studies in his book on strength training which demonstrated that heavy lifting (i.e. squats and similar movements) is very protective against heart disease with no added cardio.

chuck said...

I heard it said that sprinting for a few minutes a day, is more beneficial to the heart that hours of walking, is that a myth, or is backed up by scientific studies?

Also, does exercising *REVERSE* years of inactivity, or does it simply halt the the progression of coronary disease? Although not exactly defined, I'm assuming heart disease means arterial plaques?

Ned Kock said...

Hi Michael, thanks. I wouldn't be surprised, even though most health markers (e.g., SBP, HDL, resting heart rate) seem to respond better to endurance exercise.

Ned Kock said...

Hi chuck.

Re. sprinting, that would be consistent with the results of this study. Not really a myth, even though walking is also a very good exercise.

Ned Kock said...

Heavy activity can reverse the damage to a certain extent, but with a CAD dignosis one should be careful. The chance of sudden cardiac arrest in those with CAD goes up a lot.

Anonymous said...

A friend of mine, age 65, "died" after a strenuous weightlifting session. I put died in quotes because while his heart stopped and he collapsed his wife, who was with him when it happened, was able to perform CPR until the EMT's got there, which changed the outcome from death to life. He spent some time in the ICU but now, months later, he has no permanent heart damage and has been released for exercise with no restrictions! I bring this up to ask the question - is there a metric out there on strenuous exercise contributing to surviving a heart attack? (He had been doing heavy weightlifting for some years before the event - did this strengthen his heart and affect the ultimate outcome?)

Ned Kock said...

Hi Anon.

This is an interesting story. I wonder if what he had was a heart attack (myocardial infarction, where heart cells die) or something else, like a seizure?

The data on this post suggests a protective effect of heavy physical activity, but I am not sure it would be enough to reverse the negative effects of a MI.