I feel like a mosquito at a nudist colony...I don't know where to start.

In general, Dr. Douglass overstates his case.

The HIIT protocol that he describes (1m sprint/1m rest x 10) isn't really representative. Typically, therapeutic HIIT sessions are 30s sprints between 4 minute rest periods repeated 4-6 times, a grand total of 3 minutes of exercise.

It's true that >90% MHR is the target, but that heart rate is achieved at the end of a sprint interval and lasts, literally, only a few seconds. Most of the people who do this kind of research think that the brevity of the sprints "buffers" the heart from stress.

Use of the term "mainstream" always raises a red flag for me. Advice isn't really mainstream or "alternative", there's either evidence that it has some benefit or there isn't.

I don't disagree that you can achieve normal blood sugar through diet alone, but you can add to that benefit with exercise, and that applies to blood pressure and heart-disease, as well. Anyway, life isn't just about blood sugar tests. Exercise will improve your overall quality of life, especially as you get older.

It's also true that there are risks associated with vigorous exercise, one of which is "cardiovascular events" but, like everything else, you have to balance the risks with the benefits. Your own doctor will have the best idea of whether or not the benefits outweigh the risks for you.

I've got a couple of blog posts about HIIT that I think are informative. You can look at them here: http://aworldlymonk.wordpress.com/

Finally, Dr. Douglass doesn't offer any evidence at all that what he says about exercise and heart attack risk is true. The evidence we do have suggests that, long- term, exercise reduces the risk of heart attack.

Sam