Too Much of a Good Thing?

26 10 2010

Can you really have too much of a good thing? The conventional wisdom would say no when it comes to things like exercise. Yet, we have recorded that extremes can have consequences. For example, for women who do some extreme marathon running, it can affect their menstrual cycle and cause amenorrhea. When it comes to cardiovascular health, the thought was that you cannot really over work the heart muscle.

A recent study by marathon runner and Canadian cardiologist, Dr. Eric Larose suggests differently. First and foremost, please note that any cardiac muscle damage appears transient and completely reversible. That being said, it appears that stress of marathon running does cause heart muscle damage.

The study was presented at the 2010 Canadian Cardiovascular Congress. It involved analyzing twenty marathon runners of varying experience; for some it was their first marathon, for others it was their thirtieth. The average age was forty-five. [i]They were examined six to eight weeks prior to the marathon, immediately after the marathon and then three months later.

The findings suggested cardiac stress similar to that which might be seen with a mild heart attack. There was inflammation and about fifty percent of the heart was involved. The less fit runners had higher levels of stress. Regardless, by three months all signs of marathon induced trauma were no longer present.

Interestingly, a recent animal study looking at oxidative stress on the heart which also causes an inflammatory reaction was found to have potentially beneficial effects. Conventional wisdom has held that oxidative stress causes a cardiac inflammatory response and thus is a bad thing. This type of reaction was the target of many studies looking to use high levels of antioxidants to reduce the effect, or prevent oxidative reactions from occurring. The recent animal study showed that these lower intensity oxidative reactions caused the heart muscle to respond by producing more blood vessels, and this response to the inflammation helped make the heart less susceptible to permanent damage from major stressors down the road. Thus these reactions served to condition the heart to be more resilient and less likely to develop permanent heart muscle weakness. This may explain why at the end of the day, the many studies looking for a benefit to taking high levels of anti-oxidants has not really panned out[ii].

What can we glean from this recent data that seems to fly in the face of conventional wisdom?

I think there are a few take home points:

  • While it is good to push the boundaries, sustained excess (of any activity) can be a detrimental practice
  • Physical exercise has tremendous benefits, be smart about how far you push. Learn to listen to your body
  • With respect to physical exercise, do not go directly from the couch to running a marathon

The human body is incredibly complex, what is the conventional wisdom of today may be the forbidden tenet  of to

[i] (Doheny, 2010)

[ii] (Zhang, et al., 2010)




5 responses

26 10 2010

Great points to bring up and share! I think, well my UN professional opinion is that a lot of it depends on your genetics. I come from longevity, no matter what abuse they did with food, alcohol and drugs, but I am not saying that its right, just seems people are different from genes to genes…I have no energy or breathe to run marathons, but could cook one, lol! Your awesome Doc! Thanks for this…

Chef E

26 10 2010

You have a point Chef, and I am sure genetics do have something to do with it. But although the sample size is small (only 20 subjects) ALL of them had heart muscle damage to some degree, and the degree of damage correlated with training. I think it might be unlikely that all 20 shared the same gene-unless it is on the crazy gene that makes you run marathons!

27 10 2010
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5 11 2010
Cajun Chef Ryan

Hey Doc,
Sounds like a perfect reason for me to limit my marathon running…oh that’s right, I have never run in a marathon. However, I did run in serveral 10K races in my youth, came in at 55 minutes the first time and around 45 minutes the other time.

I like the “everything in moderation” mantra, and with that, I’ll have another cup of tea thank you!

Bon appetit!

5 11 2010

Thanks Chef-I’ll have another glass of Cab 😉

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