Should I be Dead or Something?

Yesterday I read yet another article about High Intensity Training. The idea of HIT is that rather than exercising for a long time at a steady pace, you do a series of short, explosive all out bursts with cooldowns in between - intervals to the max. Well, that seems good to me; less time exercising, and really only a few minutes of pounding on my oh-so-fragile lumbar disks. So today I decided to try it out on the trail. 

My target workout was five minutes of warmup, six intervals of 30 seconds all-out followed by a minute of recovery, then five minutes or so of cooldown - about 20 minutes total. My supposed max heart rate is somewhere in the 170's, depending on which formula you use. They say you shouldn't exceed 80% of that, or the upper 130's for me. However, my usual runs or erging sessions take me to about 145-150. Well, take a look at the accompanying chart. For the first three intervals not only was I above 80%, I was well above my supposed 100% heart rate (note the horizontal line) - the first interval was up over 200 BPM. You could tell I was more tired and not pushing as hard in intervals 4-6.

So, someone with a "max" HR of 174 getting his heart pumping over 200 BPM? Is that healthy, even for a minute or so? Is it normal to like doing this sort of thing? The funny thing is that I used to run this hard when I took the bootcamp class to try and keep up with Glenn and John, the two really fast runners in the class. I never thought anything of it. However, seeing the data on my HR gives me a different viewpoint. Damn quantitative information is gonna make me back off a little bit next time. Maybe.