-At the end of marathons, runners have been shown to have elevated troponin levels, a markers of heart muscle damage. They may also have elevated CPK levels, representing skeletal muscle damage. The consequences of these abnormalities are not known.
-One study found that there was MRI evidence of dysfunction of the right ventricle of the heart. This was a transient finding, and, again, the long-term consequences aren't known.
-Arrhythmias, such as atrial fibrillation, are more common in endurance athletes.
-Athletes have died during Ironman distance triathlons. That said, athletes have died during marathons, half marathons, and shorter distance triathlons, and the incidence of sudden deaths during the Ironman is no greater than any other distance race.
-Long-term marathon running increases the amount of calcium in the coronary arteries, which is a marker of coronary plaque.
-Blood markers of inflammation are higher during intense training.
Me -- on my way to becoming an IronMan!
So what about me?
I'm a triathlete, who has completed 13 marathons, an Ironman triathlon (Ironman Lake Placid 2010), countless other road and trail races and triathlons of other distances, and next weekend I will be running my first ultramarathon, a 50-k (31 mile) race.
I've had an arrhythmia -- AV nodal re-entrant tachycardia, a form of SVT (supraventricular tachycardia). I underwent a successful ablation procedure in April 2009, and have had minimal palpitations since. To my knowledge, AV nodal re-entrant tachycardia is not an arrhythmia that is encountered any more frequently in athletes than in non-athletes.
During my Ironman Lake Placid training, I did some blood work. My cholesterol numbers rocked, my hemoglobin was well within the normal range, and electrolytes were good, but my high-sensitivity c-reactive protein level, a marker of inflammation, was quite elevated at 7.4, with normal being levels less than 2.
As I trained for Ironman Lake Placid, I was tired all the time. I didn't feel good. My run times dropped, and I slogged along on my long 15 to 20 mile practice runs at an 11 to 12 minute per mile pace. I couldn't wait for my 6+ hour long bike rides on Pacific Coast Highway to be done. And the swimming... I've never been a fan of long swims, so the day I had to swim two miles, thankfully my friend Ray was there to entertain us with the occasional group hug or joke, as we then doused our faces in the water and stroked on to the finish.
I finished Ironman Lake Placid in 14 hours and 45 minutes. I see my friends and teammates who have done multiple Ironman races. I contemplate how on a flat course and the right training I could finish in under 13 hours. Because I could achieve that. I even thought about signing up for Ironman Arizona 2013. Fortunately, when the race went on sale last Monday morning at 11 AM, I was busy with patients and wasn't bored at my computer to repeatedly hit the "refresh" button.
But, if I were honest with myself, I don't want to do another Ironman. I will do an ultramarathon for the same reason I became an Ironman -- to say I've achieved that distance.
I'm not going to be an endurance athlete forever. I'll always be physically active, and I hope that during the length of my "career" as an endurance athlete that I can take away the health benefits and not be left with the possible consequences.