Discussion: Arrhythmias and exercise: Sensible, mostly good news

As long as scientists make good research and journalists keep that fraud O'Keefe out and refrain from The Anecdote of Micah True, things look pretty much like what one would expect, consistent with prior observations and common sense.

Is atrial fibrillation more common because VF is more likely to be lethal, or is the incidence actually skewed more towards AF? In general, not just fit folk.

It's weird, when I saw someone else had posted in this thread that I had no comprehension about the meaning of, I immediately thought "I wonder if it's Tooms responding" and here you are.

My understanding is that the atria are a system in which it's easier to establish an oscillation vs. the ventricles. Lower phase margin. Your understanding may vary depending on your background.

I believe you have it right, Tooms. A-fib is a condition that makes you feel weird, and seriously reduces your ability to do anything active while it's happening because you can't get increased blood flow going well. V-fib is also called a heart attack, and if something doesn't happen to get you out of it in short order, you die, because you have essentially no blood flow.

TD is right, apparently AF is very common and can be precipitated by all sorts of things that ultimately affect the conduction. MIs cause VF but infrequent compared to AF.

I am a long-time, fairly well-trained orienteer who developed AFib a few years ago at age 67. In my consequent web research on this problem I was pleased to find a study by J. Karjalainen and four other Finns "Lone atrial fibrillation in vigourously exercising middle aged men: case-control study", BMJ 316:1784 http://www.bmj.com/content/316/7147/1784.1 . In 1995 they studied the "60 top-ranked orienteers in 1984" from M 35- to M55-, and found a higher incidence of lone AFib than in the general population. Lone AFib means no other heart symptoms. I am happy to be able to blame my AFib on orienteering (and now mountain running) training. I get it every few months, and take 3 flecainide pills, which get me back into sinus in several hours.

Yes, the numbers for afib are something like 12% incidence in x-c skiers, 7% in runners, 5% in orienteers (in the above BMJ paper and there was also one done on British orienteets, with very similar numbers for results.). To me, this shows a correlation with volume of aerobic activity; skiers do more than runners, who do more than orienteers. These are of course blanket statements without stratification for age, length and intensity of exercise, etc. Sorry about the lack of rigor in this post and I encourage everyone to verify my claims and post links to the related articles.