A fellow coach, Steve Diggs, sent me the link to this research paper. Several years ago, Steve and I had a discussion about high intensity training (HIT) programs that other coaches were using, as well as repeated training for Ironman distance events. The short of the discussion is that we both had a gut feeling that there is some top limit for the volume of HIT and overall volume of endurance training where if you go over that limit, it is harmful to your health.
Now there is research that is backing up our gut feelings. Here are a few key plucks from the research paper:
· Mohlenkamp et al studied 108 middle-aged German long-term marathon runners and compared them with matched nonrunner controls. They observed a greater atherosclerotic burden in the marathoners as documented by higher coronary artery calcium (CAC) scores.
· Indeed, long-term sustained vigorous aerobic exercise training such as marathon or ultramarathon running or professional cycling has been associated with as much as a 5-fold increase in the prevalence of atrial fibrillation.
The conclusion of the investigation follows:
In some individuals, long-term excessive endurance exercise training may cause adverse structural and electrical cardiac remodeling, including fibrosis and stiffening of the atria, right ventricle, and large arteries. This theoretically might provide a substrate for atrial and ventricular arrhythmias and increase cardiovascular risk. Further investigation is warranted to identify the exercise threshold for potential toxicity, screening for at-risk individuals, and ideal exercise training regimens for optimizing cardiovascular health. For now, on the basis of animal and human data, cardiovascular benefits of vigorous aerobic exercise training appear to accrue in a dose-dependent fashion up to about 1 hour daily, beyond which further exertion produces diminishing returns and may even cause adverse cardiovascular effects in some individuals.
While it currently appears the researchers are saying “some individuals” – the endurance sports and intensities that some of us do repeatedly “may not” be good for overall health.
If it turns out that anything over an hour a day is bad for you – will you give up doing the distances and intensities you love so much?
Or – will you say everyone must die of something and if doing endurance sports year after year does it, I’m okay with that? (Comments can be added on Facebook. )
Note: Find the full article here, including a video interview with the author. The short video is worth watching.
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