https://www.nytimes.com/....html?smid=url-share

Some of the comments to the article are a little too spot on for me....

Just to be clear on what "links" means in this context.

The NYT article mentioning triathlon as an example of "extreme endurance exercise" references this 2016 article (not study) titled, Pathophysiology of atrial fibrillation in endurance athletes: an overview of recent findings. That article then references this 2009 study to justify the claim of increased rate of a-fib among "young" endurance athletes. And young is in double finger quotes for me since the median age in the study was 51. But I'm happy to call myself "young" at 50. That 2009 meta analysis did not include the words triathlon/triathlete. It included marathoners, cyclists, orienteers, and the rest were classified as "mixed sports". "Mixed sports" very possibly includes "triathlon," but that's unclear to me, and I didn't feel like delving down another layer in the reference chain.

I'm not calling any of those articles/studies wrong/bad.

Just pointing out that a) the NYT is not using new information, and b) "triathlon" is apparently just used as an abstract example of "extreme" endurance exercise - there is nothing unique to triathlon that's part of the discussion, as far as I can tell.

So, I only follow the a fib and endurance sport link casually (As I am fortunate not to have had a fib yet).

Doo you know whether the question has been answered or studied as to whether it's the duration of training or the intensity of training that leads to increased risk of a fib. It's my recollection that at higher intensities you have more inflammation (though I could be completely wrong on this) which had been the way many of us trained these past few decades. Given the larger focus given to training in zone 1 and 2, would the risk be significantly lower for people who are able to practice such an approach. another musing ive had. . . I wonder if those elite athletes that Stephen Seiler described who did a 80/20, did they have an increased probability to the development of a fib.

Lost me at NYT

There's a relatively, or at least more, recent meta-analysis here:

https://bjsm.bmj.com/content/55/21/1233

It suggests a smaller estimated association than in some of the earlier papers. Also, the association is stronger for non-endurance sports, and importantly there's a pretty substantial suggestion of publication bias in this area. The publication bias issue is sort of buried in the supplementary materials, and is enough for me to think the apparent association is probably nonexistent.

I find this topic fascinating and wonder if there is an upper limit to how much exercise is "good." In my mind, it's entirely possible those with AFib were at risk and long term exercise is associative rather than causational. I'd love to hear more from those who know this area well.

the ACC recommends 150 minutes of moderate exercise on a weekly basis-basically 5 x 30 minutes of some kind of activity *(walking/running/cycling/swimming, moving...)




Promoting Physical Activity and Exercise: JACC Health Promotion Series | Journal of the American College of Cardiology

Top 10 Take-Home Messages for the Primary Prevention of Cardiovascular Disease
1. The most important way to prevent atherosclerotic vascular disease, heart failure, and atrial fibrillation is to promote a healthy lifestyle throughout life.
2. A team-based care approach is an effective strategy for the prevention of cardiovascular disease. Clinicians should evaluate the social determinants of health that affect individuals to inform treatment decisions.
3. Adults who are 40 to 75 years of age and are being evaluated for cardiovascular disease prevention should undergo 10-year atherosclerotic cardiovascular disease (ASCVD) risk estimation and have a clinician–patient risk discussion before starting on pharmacological therapy, such as antihypertensive therapy, a statin, or aspirin. The presence or absence of additional risk-enhancing factors can help guide decisions about preventive interventions in select individuals, as can coronary artery calcium scanning.
4. All adults should consume a healthy diet that emphasizes the intake of vegetables, fruits, nuts, whole grains, lean vegetable or animal protein, and fish and minimizes the intake of trans fats, processed meats, refined carbohydrates, and sweetened beverages. For adults with overweight and obesity, counseling and caloric restriction are recommended for achieving and maintaining weight loss.
5. Adults should engage in at least 150 minutes per week of accumulated moderate-intensity physical activity or 75 minutes per week of vigorous-intensity physical activity.
6. For adults with type 2 diabetes mellitus, lifestyle changes, such as improving dietary habits and achieving exercise recommendations are crucial. If medication is indicated, metformin is first-line therapy, followed by consideration of a sodium-glucose cotransporter 2 inhibitor or a glucagon-like peptide-1 receptor agonist.
7. All adults should be assessed at every healthcare visit for tobacco use, and those who use tobacco should be assisted and strongly advised to quit.
8. Aspirin should be used infrequently in the routine primary prevention of ASCVD because of lack of net benefit.
9. Statin therapy is first-line treatment for primary prevention of ASCVD in patients with elevated low-density lipoprotein cholesterol levels (≥190 mg/dL), those with diabetes mellitus, who are 40 to 75 years of age, and those determined to be at sufficient ASCVD risk after a clinician–patient risk discussion.
10. Nonpharmacological interventions are recommended for all adults with elevated blood pressure or hypertension. For those requiring pharmacological therapy, the target blood pressure should generally be <130/80 mm Hg.





long term endurance athletes and afib is a different question...and then it gets somewhat sticky...

so, it's long been known that endurance activity is usually associated with increased episodes of p-afib-I remember talking with Dr. Aaron Baggish about this many years ago before it got into the literature.

He eventually published a paper on athletes and cardiac issues.

Athlete's Heart and Cardiovascular Care of the Athlete | Circulation (ahajournals.org)



This is a nice little graph from a different paper:



UP TO DATE-has this to say:
Regular physical activity — The relationship between physical activity and the development of AF is uncertain. Some [145-147], but not all [148-150], studies have suggested that regular physical activity is associated with a risk of AF in the general population. In a 2013 meta-analysis of four prospective cohorts (n = 43,672), and after dividing subjects into four or five groups on the basis of cumulative physical activity per week, there was no difference in the risk of AF comparing patients in the maximum and minimal groups (odds ratio 1.08, 95% CI 0.97-1.21) [151].





145.Mont L, Tamborero D, Elosua R, et al. Physical activity, height, and left atrial size are independent risk factors for lone atrial fibrillation in middle-aged healthy individuals. Europace 2008; 10:15.
146.Aizer A, Gaziano JM, Cook NR, et al. Relation of vigorous exercise to risk of atrial fibrillation. Am J Cardiol 2009; 103:1572.


147.Elliott AD, Linz D, Verdicchio CV, Sanders P. Exercise and Atrial Fibrillation: Prevention or Causation? Heart Lung Circ 2018; 27:1078.
148.Everett BM, Conen D, Buring JE, et al. Physical activity and the risk of incident atrial fibrillation in women. Circ Cardiovasc Qual Outcomes 2011; 4:321.



Multiple studies have reported that the rate of atrial fibrillation (AFib) in endurance athletes is two to 10 times greater than in controls12. It is estimated that for every 10 years of regular endurance exercise, the risk of AFib increases by about 16%, and the risk of atrial flutter increases by 42%13. Endurance sports practice has an impact on atrial remodelling, atrial ectopy, and an imbalance of the autonomic nervous system, and may therefore act as a promoter of these arrhythmias4.

150.Lau DH, Nattel S, Kalman JM, Sanders P. Modifiable Risk Factors and Atrial Fibrillation. Circulation 2017; 136:583.
151.Ofman P, Khawaja O, Rahilly-Tierney CR, et al. Regular physical activity and risk of atrial fibrillation: a systematic review and meta-analysis. Circ Arrhythm Electrophysiol 2013; 6:252.


Ablation of Atrial Fibrillation in Athletes: PRO - American College of Cardiology (acc.org)

Atrial Fibrillation in Competitive Athletes - American College of Cardiology (acc.org)



and of course, Dan has a nice link with a lot of information about afib right her on ST in his "hot topics"

It's not just a-fib though. There are other negative effects linked to chronic endurance exercise (increased coronary plaque, myocardial fibrosis etc.).

There are two things to consider:

1. How strong are these correlations. In some cases the evidence is perhaps not so strong.

2. Are these things actually negative or simply just "different". For example while endurance athletes may have increased coronary plaque the type of plaque found in athletes appears to be a more benign type. Perhaps explaining the contradiction between increased plaque but lower mortality.

Perhaps the classic study on this topic is the Harvard alumni study which reported the reverse J-shaped curve back in the 80s. You get the biggest gains in health going from 0 exercise to a few hours. Then improvements in health become more moderate with increased time, eventually reaching diminishing returns, before seemingly becoming negative. The study found 3,000 to 3,500 kcal/week exercise was the sweet spot with a 54% reduction in mortality risk. Those doing >3,500kcal had a 38% reduction.

I would say what the studies consider "high volume" and "high intensity" would actually be considered pretty low by many triathletes. For examples low intensity typically means walking as opposed to z2.

In terms of maximising health benefits the WHO guidelines are probably pretty reasonable. Most triathletes are probably going past the point of optimising health. But you have to always remember performance and health are not the same thing. Also even if you are reaching into the area of decreased health benefits you are still way better off than the people that are sedentary.

If health is your goal many of us could probably do with dropping a couple of cardio based exercise a week and doing some extra strength work. Leg strength is a great predictor of healthy aging.

But I think potential negative effects of chronic endurance exercise is something triathletes don't talk about enough. I'm not sure if it's a lack of awareness or perhaps something we'd rather put our heads in the sand about and not consider.

Not a cardiology expert but am a public health researcher and I think part of the thing with the funnel plot in that meta-analysis (Figure S1, funnel plot) is that there *are* a lot of studies linking afib to exercise (almost all of them really), but the association goes to zero as study quality goes up, and there's a huge "missing half" of the distribution, of smaller studies that should statistically speaking be showing negative associations (that is, afib goes down with more exercise) but aren't there. It's a textbook publication bias plot, what it looks like when negative associations are selectively not published for whatever reason. If the true association were nonzero, that funnel plot would be symmetrical and centered on some positive value.

How do you understand the studies you cited? Is AF really related to long term endurance training? Is it a modifiable symptom of overtraining? AF doesn't appear inevitable for high volume endurance athletes. So what I'm really interested in knowing, and I recognize there may not be a real answer... is there an unsafe level of endurance exercise (assuming not overtrained) for an otherwise healthy individual? And with AF happen with age regardless of endurance training history? Thanks for your professional insight.

NYT is the enemy of the people.

Moderate amounts of exercise may actually lower the risk. It's high amounts of exercise that appears to increase risk.


High training volume and/or intensity =/= "overtraining" which is non-functional overreaching and may be just as much (if not more) linked to lack of recovery (e.g. reds) than training itself. Afaik there is no research looking at a relationship between the two and I'm not sure it's particularly relevant. In some of the studies in the general population the level of exercise that produced increased risk is so low it's hard to believe they would be "overtraining".


Very little is "inevitable". You could smoke 20 per day and not get lung cancer. We are talking about increasing risk.

Also volume is part of the equation. Based on some of the research and explanations of why exercise causes AF intensity may also be a factor.


One study found increased risk when doing more than 55 MET h/wk.

Not AF, but the Harvard study found those doing >3,500 kcal/week had a higher age-adjusted reduction in risk of death than those doing 3,000 to 3,500 kcal/week. Of course they were still far better off than the sedentary group.


For some people yes. There are numerous variables endurance exercise is only one.

superb response and thanks---



I've got to spend less time looking at ST-

Sorry in my above post I put higher not lower


The moderate group (3000-3500kcal) had a lower risk of death than the >3500kcal group. I.e. from a health perspective 3000-3500kcal per week seems better than over 3500kcal.

thanks for the summary, very informative. I'll give up my 20 PPD smoking habit, but sticking with the 3500+ active kcal/week for now.