A recent blog post in the New York Times Well Blog brought this to my attention – Can too much running create damage to the heart?
I would like to hope not, but this does make one think a bit in regards to how much running they are doing or should be doing.
The post references three studies. A 2011 study of male, lifelong, competitive endurance athletes age 50 or older found that they had more scarring in their heart muscle (cardiac fibrosis) than men of the same age who were active but not competitive athletes. None of the athletes had died young. A 2011 study of Tour de France riders, who train ferociously, those who had competed between 1930 and 1964 lived, on average, about eight years longer than age-matched men. The third and largest study to date, involving more than 50,000 adults and presented at the 2012 annual meeting of the American College of Sports Medicine, reveals participants who ran between 1 and 20 miles per week had almost 20 percent less risk of dying prematurely than people who didn’t exercise. But those who ran more than 20 miles per week enjoyed no such benefit. They had about the same risk of premature death as those who were sedentary. Interesting.
I did a brief review of the literature published to date on this fascinating subject and it seems the consensus is this – there has been a link between endurance training and a condition of the heat known as cardiac fibrosis. Cardiac fibrosis may cause stiffness in the chambers, valves, and arteries of the heart which can lead to arrhythmias, heart failure and even sudden cardiac death.
Not all veteran extreme endurance athletes develop this pathological remodeling, and indeed lifelong exercisers generally have low mortality rates and excellent functional capacity.
The question that arises for me is what other variables exist which could be leading to this condition. For example, well known Alberto Salazar experienced an arrhythmia which cause his heart to stop and was eventually resuscitated back to life. Many have argued that his over intense training regimens and failure to rely on heart rate during training placed him in this situation. I think the studies need to address the training parameters and intensities over a given period of years to see if there is an association. In other words, would training at lower intensities and relying on heart rate reduce this cardiac damage that is being seen in endurance athletes?