Heart damage from cardio endurance?!

Regardless of which studies you peruse however, there seems to be no conflict with the statement that moderate volume running (9-12 miles per week) at a moderate pace (7:30-8:00 min/mile) is heart healthy.

It is at the higher limits where the disagreements begin.

Yours in Fitness,

Coach Sommer

That is very correct and well stated.

One interesting thing is that the triathlon has a higher incidence of death compared running, and it's most often during the swim. There is a gene variation called long-QT type 1 (LQT1 for short) that predisposes to ventricular fibrillation with exercise, in particular with swimming, so that aspect may have nothing to do with the proposed training effects at all.

I think the discussion is interesting, but highly theoretical. And will remain speculative for many years to come.
There are associations with extreme endurance athletes, but there are a ton of different mechanisms for how cardiac injury occurs in athletes and most of them are based on certain genotypes. If you have genetic variation A, you might develop cardiac defect B if you subject yourself to condition C with a high enough frequency.

Bottom line is likely: If you spend your life going to extremes all the time, it's very likely you will have to pay for it later, in some way. But it's hard to predict how. And with exercise, more fitness is usually healthy. Like coach said, for most of us, there are other types of injuries that will be of greater concern.

Dzosh said:

One interesting thing is that the triathlon has a higher incidence of death compared running, and it's most often during the swim. There is a gene variation called long-QT type 1 (LQT1 for short) that predisposes to ventricular fibrillation with exercise, in particular with swimming, so that aspect may have nothing to do with the proposed training effects at all.

For swimming, the long QT interval leading to arrhythmia, might be related to hypoxia. I guess it will be more of an issue in swimming than in running.