Tag: cardio

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- Alex Hutchinson (@sweatscience)

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There’s an article by “paleonutrition” advocate Kurt Harris, posted on the Psychology Today website, that is currently making the rounds, in which he argues that aerobic exercise causes heart disease.  The study he’s talking about was published in Radiology back in 2009 by a German group led by Frank Breukmann and Stefan Möhlenkamp. They compared 102 marathon runners between the ages of 50 and 72 with 102 age-matched controls, and used cardiac MRI with late gadolinium enhancement to look for evidence of permanent heart damage. Five of the runners had evidence of past heart attack, and another seven had heart damage not associated with a heart attack, for a total prevalence of 12%. Among the controls, two had evidence of past heart attack, and another two had other damage, for a total prevalence of 4%.

The difference between the two groups wasn’t statistically significant. This doesn’t matter to Harris:

I am obliged to point out that by the conventional arbitrary criteria used in biomedical publishing, the difference was “not statistically significant”… Stop doing what you are told and read the statistics without letting the authors or editors tell you what is “significant”.

That’s certainly a convenient approach: if you already think you know what the right answer is, then you don’t need to worry about little details like statistical significance.

Still, the results are  very much worth considering. Harris wonders why the study was ignored by the “nutrition and fitness” blogosphere, and takes a shot at the New York Times:

[I]t’s published in Radiology, which is not exactly Gina Kolata territory.

Actually, the Times ran a Bloomberg article on the early results from this study cohort way back in 2006. And Runner’s World interviewed cardiologist Paul Thompson, a co-author of the most recent results from the study, in January. Thompson points out some important caveats about the study group:

[H]is marathon group includes a number of former smokers and others who might have been quite unhealthy before they began running…

The key issue with Möhlenkamp’s runners is that their cardiac risk scores are compared using their present cholesterol, blood pressure, and other health numbers. They might have had terrible numbers before they started running, so when their coronary calcium is compared with folks who are not athletes, but had good risk numbers all their lives, it looks like the runners had more calcium, ie, more atherosclerosis than predicted by their risk factors… Many of the runners “got religion” when they turned 40 or so.

To his credit, Harris acknowledges that 50% of the runners in the study had a history of smoking, compared to just 42% of the controls — but immediately dismisses the possibility that this (and any other underlying factors that differ between the two groups) could play a role. Again, why worry about statistics and the possibility of confounders when you already know the right answer?

Let me perfectly clear: it’s entirely possible that repeated marathon running (the runners in the study had completed an average of 20 marathons) produces damage to the heart. By all means we should continue to study this, and find out. Despite Harris’s snide comments about aerobic exercise not producing immortality, we’ve known that aerobic exercise doesn’t grant immunity from heart disease for decades. In fact, very first time noted iconoclast Tim Noakes made a splash in scientific circles was way back in 1976, with a paper about heart attacks in veteran marathon runners.

Of course, there’s a difference between running marathons and “aerobic exercise” as practiced (or not) by the vast majority of the population. I’m a lifelong runner, but if someone asked me: “What’s the optimal exercise routine for cardiac health?” I wouldn’t necessarily recommend running marathons. I’d probably suggest something like an hour a day, with two to three days a week devoted to shorter, faster interval workouts. And of course, I would also recommend doing some resistance training — and I wouldn’t take, for example, a study showing that competitors in the World’s Strongest Man competition die early as evidence that “resistance training is bad for you.”

That’s basically what Harris is doing here: concluding, on the basis of this one study of a fairly extreme group of outliers, that aerobic exercise in general is as bad for you as boxing or football. The only sensible exercise, he argues, is resistance training:

I still find no grounds at all to believe that high levels of “cardio” protects your heart or makes you live longer. Certainly not “the more the better” which is what we’ve been led to think since the 1970s running craze.

The reason he finds no grounds, of course, is that he’s never looked. In his article, he waxes philosophic about the fact that “the picture or the test result is not the patient or even the disease.” Then, on the basis of a test result, he concludes that running will kill you. But what if we look at “the thing itself,” and find out whether runners die less from heart attacks — and whether “the more the better” holds up.

Paul Williams did this study and published it back in 2009. He followed 35,402 runners for 7.7 years, during which time 467 men reported heart attacks, angina or had to have bypass surgery, while another 54 died of heart disease. The risks of all these symptoms, including death, decline with every additional kilometre run. Those running more than 9 km/day “produced risks 65% lower for angina, 29% lower for nonfatal CHD, and 26% lower for fatal and nonfatal CHD” compared to those running fewer than 3 km/day (the level corresponding to national physical activity guidelines for adults).

I’ve rambled on a bit here, so let me finish by repeating one simple point. Even if you take the results of Möhlenkamp’s study at face value (which I don’t, as explained above), the conclusion you can draw is that running a large number of marathons may damage your heart. To go from this to arguing that 20 minutes on the elliptical is bad for you requires a Beamon-esque leap of logic, along with a cheerful disregard of literally hundreds of epidemiological studies.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Just noticed a great post on Amby Burfoot’s Peak Performance blog where he interviews Paul Thompson, the Hartford Hospital cardiologist who’s the go-to guy for questions about exercise and heart health. It’s a fantastic interview, very wide-ranging, with Thompson sharing his thoughts, hunches and beliefs about a bunch of the current controversies in this area.

One part that caught my attention in particular was a question about a recent German study that found a high prevalence of hardened arteries among marathon runners (I blogged about it here). Thompson was a co-author on the study, and he shared a frank assessment of some of the study’s strengths and weaknesses:

[H]is marathon group includes a number of former smokers and others who might have been quite unhealthy before they began running…

The key issue with Mohlenkamp’s runners is that their cardiac risk scores are compared using their present cholesterol, blood pressure, and other health numbers. They might have had terrible numbers before they started running, so when their coronary calcium is compared with folks who are not athletes, but had good risk numbers all their lives, it looks like the runners had more calcium, ie, more atherosclerosis than predicted by their risk factors… Many of the runners “got religion” when they turned 40 or so.

This is a classic illustration of why a single study, or even a single group of studies, can so easily point us in the wrong direction. On the surface, it looks simple: take a bunch of marathoners, compare them to controls, and presto — marathoners have worse arteries. But it’s easy to be led astray by underlying factors (not to mention, as Thompson points out, that the hard, stable arterial plaques found in the runners may actually be a good thing, as opposed to soft, unstable plaques that are easily dislodged).

Anyway, it’s an interesting read, and Burfoot does a great job “pinning Thompson to the mat” to get his (well-informed) opinions and best guesses on a bunch of topics.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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There’s a new preprint online at Medicine & Science in Sports & Exercise, from researchers at the University Clinic Essen in Germany, describing a study of heart disease in marathon runners. They recruited 100 runners aged 50-75, all of whom had completed at least five marathoners in the previous three years, and ran them through a battery of tests to assess the health of their arteries, both in the heart and elsewhere in the body. (They used, among other measures of risk, ultrasound imaging and “electron beam computed tomography,” which I’ve never encountered before and which sounds pretty cool!)

Anyway, the gist: they found plaques in the arteries of all but 10 of the runners. They run a bunch of analyses trying to figure out how to predict what differentiates the plaque-free runners from the plaque-y runners — but eventually they conclude that the subjects at highest risk are those who would be identified as high-risk by conventional analyses (e.g. the Framingham Risk score). In other words, being a runner doesn’t exclude you from or make you immune to these conventional risk factors.

Is this news? Well, it reminded me of an anecdote Tim Noakes told me last summer, about the conventional wisdom in the 1970s that devoted runners were essentially immune to heart disease. So what did Noakes, a lifelong paradigm-buster, do? Amby Burfoot described it a few years ago in a Runner’s World article about the very first New York Academy of Sciences meeting on the running and medicine in 1976:

So Tim Noakes, M.D., gave a presentation that documented the heart attack of a veteran marathoner, which became one of the most-talked-about sessions. Prior to this, several running physicians enjoyed notoriety for claiming that a marathon finisher could never have a heart attack.

Still, it’s always good to get a reminder — or as the German researchers conclude: “These data support an increased awareness of atherosclerosis prevalence and cardiovascular risk factor in marathon runners.”

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

The issue of heart damage in marathons has been a hot one lately, in the news most recently because of a study presented at the Canadian Cardiovascular Conference in Montreal last week. Laval University researchers did an MRI study of runners before and after a marathon, and concluded the less-fit runners sustain heart damage that can last for up to three months. They suggest that runners should get a VO2max test to determine whether they’re ready for a marathon.

Three points. First, do marathons “damage” hearts? This is the second MRI study to come out in the past year or so. The previous one, at last year’s Manitoba Marathon, found damage that disappeared within a week after the race. In the new study, they’re saying three months (note: since it’s just a conference presentation, I haven’t seen the details of the study yet). So it seems clear that marathon DO damage hearts — in the same way that they damage leg muscles, neuromuscular firing patterns, and probably even motivation to run, i.e. temporarily. As far as I know, there were no lasting negative outcomes in the Laval study.

Second, are runners who train less more susceptible to damage? This is the “novel” finding of this study, though it’s pretty obvious on an intuitive level. Personally, I think it’s a pretty good message: marathons are a big endeavour, and it’s worth training properly for them for all sorts of reasons. Do I think that those who persist in jumping into marathons with inadequate preparation are tempting fate? Not really — the statistics show that marathons as a mass participation event are still overwhelmingly safe compared to the baseline risk of other activities.

Third is this warning that prospective marathoners should get a VO2max test to figure out whether their heart can handle a marathon. I’ll have to wait until the full study is published to evaluate this more fully, but I’m a little skeptical. They initially point out that the heart is divided into 17 segments, and when one segment is injured/stressed the other segments can compensate, hiding the problem:

It also makes it practically impossible for physicians to arrive at an accurate assessment of the heart health of the marathoner when only considering the whole heart.

That’s why MRI is useful, because it can look at the segments individually. But then they turn around and suggest VO2max, which is an overall measure of cardiac function (not to mention all the controversies about what peripheral factors may also play into VO2max).

It just seems to me that VO2max is a pretty blunt instrument for figuring out who’s okay to run a marathon. It’s also a difficult, time-consuming and inconvenient test to run — so I’d like to see some assessment of what negative outcomes, exactly, we’d be hoping to avoid in exchange for the time and expense of hundreds and thousands of VO2max tests. Is it the handful of yearly deaths in major marathons (many of which would NOT be predicted by screening programs like this)? Or is it to prevent the temporary, invisible heart damage that marathoners have apparently been suffering with no ill effects for years?