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Heart Damage from Excessive Endurance Training?

Mike G writes:

As a long time cyclist, Moots owner and Mac user, I enjoy your blogs and analytical insight. I was wondering if you ever commented on, or would be willing to offer your thoughts on the VeloNews article from last year on heart damage from excessive endurance training, or James O'Keefe's comments on the subject (Cardiovascular Damage From Extreme Endurance Exercise) who recommends limiting training to 45 minutes a day, especially for those over the age of 40.

WIND: I need to take the time to read these articles in detail.

The sun was bright upon the upturned redrock Flatirons above Boulder, Colorado. It was a beautiful July morning in 2013. Lennard Zinn, a world-renowned technical cycling guru, founder of Zinn Cycles, longtime member of the VeloNews staff, lover of long rides, and a former member of the U.S. national cycling team, was riding hard up his beloved Flagstaff sxMountain, a ride he had done a thousand times before.

But this time, it was different. His life was about to change forever. When his heart began to flop like a fish in his chest, and his heart rate jumped from 155 to 218 beats per minute and stayed pegged there, his first reaction was simple: “I went into denial.”

In general, I’d call out these as context:

  • Small-scale studies are inherently questionable.
  • There is a wide range of physiology out there, intensity of workouts, diet, genetics, etc. What about alcohol or too much sugar?
  • Drugs can be involved: if anything I know that antibiotics can cause severe neuropathy (I have mostly but not fully recovered, but it took 18 months). So what other factors or drugs might associate or exacerbate issues with the heart? Including “Vitamin I” (ibuprofen and its ilk).
  • Medical science has a poor understanding of what causes disease at the specific individual level. I’m not an average; I’m me. Heck, my HDL never drops below 84 and has hit 104 or close to it on many testing occasions, so why shouldn’t all sorts of other things vary in good and bad ways for specific individuals?
  • Quality of life matters. Most people my age would suffer miserably doing the things I love (hiking at high altitude, cycling extensively, etc). The better the shape I’m in, the better I feel.
  • I personally will take on the alleged risks, and I’ll continue eating eggs which are now back in favor after being put on the food sh*t list for so many years. And I’ll enjoy salt too, which science now realizes is far more risky as for too little vs too much. So much “science” is often based on weak evidence. And then there is junk science such as BMI which is really epidemiology with the resulting medical malpractice in applying statistics to specific individuals (I have been borderline obese for years according to BMI).
  • What is “normal” anyway? These days “normal” is a over-fed fat slob. Just take a walk through a mall, or Disneyland. I’m not sure science actually has any proper baselines in terms of humans.

All that said:

  • I love doing double centuries. What is in the article is scary stuff. I do not WANT to believe it. But that would be stupid: I take the evidence as a serious concern. I will be watching myself more carefully.
  • All my ECGs have been entirely normal.
  • Where is the Apple iWatch monitoring graph for heart oddities? That would be cool.
  • I have had an irregular heartbeat when extremely well trained (skip a beat, then a hard beat to continue). This only happens when I’m in peak condition in both in endurance and strength. This year only a little of that perhaps because I did little ultra-hard effort training.
  • Once (and only once) I felt faint and dizzy and had my heart race during a personal best effort up Old La Honda. A brief pause and I resumed without incident. It was hot and who knows, but no further thing like that.

I’ve had the “skipped beat” thing, and I’d swear it is exactly that:

When we train intensively for an endurance event, several adaptations occur in our hearts. The most common is that our resting heart rate goes down due to improved heart function. Many endurance athletes will experience what they think is the sensation of their hearts skipping a beat. Actually, this is most often due to premature beats — a premature ventricular contraction (PVC) if it originates in the ventricle or a premature atrial contraction (PAC) if it originates in the atrium. Both PACs and PVCs are quite common in well-trained athletes and often are not dangerous.

I start to get extremely skeptical when I read a passage like this, which calls a rate under 60 “ultra low”. Weird.

The athlete’s heart lurches from extreme to extreme — from spikes approaching 200bpm to long periods of ultra-low resting heart rates below 60bpm, a condition called bradycardia.

How the heck can “normal” be what physicians see every day: obese couch potatoes? Is this a case of improper context? My heart rate never goes over 175 these days, and rests from 39 to 49, depending on recovery, etc. I record everything (every beat) so I don’t think there is any doubt about the rates. I used to record morning before getting out of bed patterns, for several minutes. Nothing unusual. My last physical (for life insurance), my HR was resting at 42 at 10:00 AM.

On the other hand:

Other studies have shown that Tour de France riders and other former professional athletes live lon- ger than average, and often have lower rates of heart issues later in life. Maybe that sounds counterintuitive, because often these athletes are riding in volumes that far exceed even those of the most addicted masters endurance athlete. But there’s a key difference. The pro athletes did it, then quit and didn’t continue to do it later in life. Masters athletes? They just keep plugging away, with the mindset that if they train like Contador, they’ll be able to ride like Contador. Year after year, decade after decade, it adds up.

Still, there is no arguing that physical activity is an effective, efficient, and virtually incomparable way to care for your heart, fight cardiovascular disease, and prolong your life. For every journal article that says endurance athletics is hurting their heart, there is one that says the opposite. Or maybe two.

But, like many other medicines, more isn’t always better. Research is honing in on the issue of dosage in exercise. If you think of exercise as a drug, there is a certain threshold at which good becomes bad, when benefit becomes detriment. When is too much? Is everyone the same, or are some predisposed to risks of extreme exercise? Is intensity as bad as duration, or duration as bad as intensity? Is it only bad if repeated over years or decades? The science is new when it comes to the science of overdosing on exercise.

I have found that life (my life) goes in 10 year cycles. As I proceed into my 50’s I intend to continue doing double centuries. But already I tend to make that only 3 monthf of the year (March through June). Then I enjoy hiking and such while biking “only” 60-90 minute a day or so. I’m just going to keep doing what I like to do until what I like to do changes, or until I get a bad suprise—I’m not going to do one of these unsubstantiated “what if” things, giving up something that quite possibly need not be given up.

Finally, what could I do about it anyway? I’m at least 1 in 10,000 in terms of exercise at my age, so how many doctors even exist there with the context of hard-core people like me? And no one is an average, so even the best doctor is dealing with an individual, and statistics applied to individuals are not science.

Video by Dr. James O'Keefe MD: Cardiovascular Damage from Extreme Endurance

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