A friend of mind sent me a similar article when I mentioned that I was getting a TT bike. Ironically the guy who sent me the article is a very fast competitive ultra guy who was making the argument that a 20k TT was going to wreck my heart. But the point was well-taken, his concern was running at max HR for 30 min or 60 min or in my case maybe 90 min was worse than riding a 500 mile race I which you vary your HR and effort a little more and of necessity ride with lesser intensity.

Who knows what is right, but it's worth being aware of. I'm increasingly capable of pushing myself at high intensity for long periods of time. I enjoy riding like that, it's very "cleansing". Is it good for me? I honestly am not sure.