So what happens when the studies show it might not be so good?


David Yon,


There are up to 30 runners traveling from Tallahassee to Boston within the next two weeks to join nearly 36,000 other runners with the goal of finishing the Boston Marathon. The reasons for wanting to run this year vary among the participants, although I suspect nearly all will have last year’s bombings on their minds.

A friend recently circulated an article to our running group from the Kansas City Star with the headline “Walk away from excess running.” The study suggested that runners who had completed 25 or so marathons might have negative health effects that undid some of the benefits of more moderate exercise. I do not think I ever believed that running a marathon was “good for you.” After all, if a runner is trying to find the maximum amount of pain and exhaustion that can be endured while running 26.219 miles as fast as possible, it is not likely to be pretty. If everything goes just right, “the collapse” will occur just after the finish.

So, it is not a shock to hear of a study suggesting potential adverse cardiovascular effects may result from excessive endurance exercise. In reality there are a number of studies on this topic James H. O’Keefe did a though review of them.

The article highlighted the following points:

  • People who exercise regularly have markedly lower rates of disability and a mean life expectancy that is 7 years longer than that of their physically inactive contemporaries. However, a safe upper-dose limit potentially exists, beyond which the adverse effects of exercise may outweigh its benefits.
  • Chronic intense and sustained exercise can cause patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, creating a substrate for atrial and ventricular arrhythmias.
  • Chronic excessive sustained exercise may also be associated with coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening.
  • Veteran endurance athletes in sports such as marathon or ultramarathon running or professional cycling have been noted to have a 5-fold increase in the prevalence of atrial fibrillation.
  • Intense endurance exercise efforts often cause elevation in biomarkers of myocardial injury (troponin and B-type natriuretic peptide), which were correlated with transient reductions in right ventricular ejection fraction.

Thanks goodness the abstract also qualifies its observations about excessive running: “this concern is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity.”

Confusing? Someone once postulated that marathon runners would be immune from heart disease. We all knew that was not true – all we had to do was look around and see the runners who died from heart disease. But, that is very different than thinking hard training might actually makes us more venerable, not less. How can something so good for us potentially turn on us like that.

Yet, I still vividly remember racing an ambulance to the hospital emergency room may years ago with Mary Jean barely conscious and her heart racing at nearly 300 beats per minute. It took three hospitals and multiple physicians to finally get her ventricular tachycardia under control. Irregular heartbeats seem too common among my running friends.

Tim Noakes, a South African professor of exercise and sports science at the University of Cape Town and author of The Lore of Running has spent his life study the impact of exercise. After reviewing the article, Noakes asked: “Time to quit that marathon running?” “Not quite yet!” There is still hope that this important part of the sport we love may still be our friend, not an enemy. As Noakes says,

“This finding does not fit with the accepted belief that exercisers have improved cardiac health and greater longevity. It suggests either that the benefits of exercise are a parabolic rather than a linear function of the amount of exercise performed so that a threshold exists above which the beneficial effects are lost. Or else those persons who persist in running more than 20 marathons have other biological or psychological factors that act against good long-term cardiac health….Clearly more work is required to exclude this potential bias.

Of course Noakes has completed 70 marathons and ultramarathons. Still, he recognizes that “the presence of high CAC [coronary artery changes] scores predicts increased risk for cardiac events. Thus runners with high CAC scores, with or without myocardial fibrosis, should be targeted for advice about the desirability of their continued marathon running.”

This research involves a very complex set of factors and interactions that are difficult to analyze. While I love both the physical and mental health and fitness benefits I have enjoyed, I have always said I would probably keep running even if I knew the data said it would shorten my life. I doubt anyone in the Tallahassee group will decide to avoid Boston based on Dr. O’Keefe’s article.

And yet, it is hard to forget those we have lost and almost lost. So, I am glad to see the well done studies continue. It sure gives us plenty to think about on during our long runs.