Atrial Fibrillation and Cycling

Assessing the Risk

Here is a paradox. There is universal agreement that aerobic exercise has many benefits to heart health, However there may also be an uncomfortable correlation between long term cycling training and the increased incidence of Atrial Fibrillation (AF)

In this weeks piece, I will aim to:

- Detail the symptoms of AF

- Describe the trigger factors

- Provide a brief overview of some of the research

- Examine possible ways to mitigate the condition.

AF has been at least partly responsible for ending the careers of some of the very best pro-cyclists. These include Sonny Colbrelli, who won Paris Roubaix, Mick Rogers, one of the best riders against the clock the world has seen and most recently, Nathan Van Hooydonck, a Super-Domestique with the all-conquering Jumbo Visma team until his early retirement. However, AF can effect anyone who has been riding their bike for a long time, particularly older, male, endurance cyclists (the prevalence is far higher in men for reasons not fully understood)

AF is characterised as palpitations or a fluttering sensation in the chest or a rapid, irregular heartbeat. This can lead to shortness of breath, fatigue, dizziness or light-headedness and chest pain. Instances can be temporary and have few if any side effects. However, AF can also develop into a longer term more persistent or even permanent condition.

Some of the main causes of AF in the sedentary population include, obesity, stress, high blood pressure, and congenital heart defects, too much alcohol, caffeine or nicotine, infections, like flu, diabetes, electrolyte imbalances, and older age.

There is also a body of evidence that long term aerobic exercise can increase the incidence of AF:

A study in Norway, comparing over two and a half thousand long distance skiers with a sedentary population of the same size, found that the over 12% of skiers self-reported symptoms of AF. On testing however, only 5.33% were found to have AF compared to 5.07% of those who were not doing exercise.

Of the skiers, just over 50% of those tested had intermittent AF, some 23% reported the condition as persistent and 24% permanent.

While the differences between skiers and none skiers may not seem significant, another study into the growing population of veteran endurance athletes who are still doing training and competitions, found that remodelling of the structure of the heart due to exercise over an extended period, may act as a promotor of AF.

The study concluded that AF increases substantially in the aging athlete, which is associated with an accumulation of lifetime training hours and participation in competitions and that a recent meta-analysis revealed a 5-fold increased risk of AF in middle-aged endurance athletes with a striking male predominance.

From personal experience, I have had short-lived bouts of AF, always after multi-day rides or races or if I am training a lot in hot weather or on my turbo and losing a lot of electrolytes through sweat.

When I finished one 8 day ride, and did a deep dive into causes and possible mitigations. I found that a very high refined sugar diet whilst fuelling my long rides was one possible cause as was the loss of vital electrolytes.

Resting post ride, I cut our refined sugars and upped my consumption of Magnesium, Calcium and Potassium. The issue resolved itself over a couple of weeks. I also had a detailed assessment from a Sports Cardiologist who told me I had little to worry about, although he did point out that there are very few people in their mid-sixties doing 2500 km bike races, so the research base was a little thin.

Researchers recommend a number of steps for those with more persistent AF. These include continuing with moderate aerobic exercise as this improves heart function and has many other benefits to overall health.

One researcher states the ‘recommended dose’ is 210 minutes of moderate to vigorous aerobic exercise a week to reduce the symptoms. The American College of Sports Medicine recommends aerobic training 3–5 days per week at 50%–80% heart rate, with sessions lasting 30–60 minutes.

A further piece of research concludes that it is only over 20 hours per week of exercise training that the risks of AF might increase!

This was backed up by some research from New Zeeland that found that there was no increased hospitalisation from AF in none elite cyclists compared to the whole population and that the level of activity undertaken was unlikely to be sufficient to increase the risk

So the research is not particularly conclusive. My take away from this would be:

- Consult your doctor if at all concerned.

- If your AF is acute and persists, avoid prolonged endurance activities

- If you are doing ‘normal’ amounts of riding your bike, continue to do so, the benefits far outweigh the risk of temporary and passing bouts of AF.

- It is unlikely that the vest majority of non-elite cyclists will do enough training over and extended period to cause AF.

However, the prescription is highly dependent on an individual’s health status and exercise training background and the persistence of their AF symptoms. The key recommendation is to consult with your Doctor and request some tests and a meeting with a cardiologist with an interest in sports medicine.

My own conclusion is that the myriad benefits of riding my bike far outweigh the very small discomfort of passing AF. I plan to continue to ride and race while making sure I keep my electrolyte level in balance too.

If any readers have specific experience of AF they are prepared to share, I can collate this and push it out to everyone. I am particularly interested in exercise induced AF and what people are doing to ameliorate the condition.

Thanks, and best wishes

Mike

Here are two links to books I have written about cycling:

The first one is about preparing for a riding the epic Pan Celtic Race last year. I was the oldest finisher of this 2400km journey through the Celtic lands. Finishing it was one of my proudest achievements.

Do Not Hurry Do not Rest

I also wrote a collection of stories about my life on a bike, a not too serious look at the very serious business of riding, racing, success and failure. This book includes the extract about my early years as a very average time trialer.

Motion and Emotion