Heart rate and training zones

This isn't a typical post for this blog, but I wanted a referencable place for me to record down some things RE: heartrate and training zones. Perhaps some others will find it useful as well.

The formula I am currently using is called the Karvonen formula, which is fairly widely accepted, given that each person varies quite a bit and no formula is perfect. I like it better than the traditional formula (220-age) because the traditional one is not realistic, for many reasons. For example, someone my age looking to exercise in the moderate training zone (75%) would be going for a HR of around 141. That is unrealistically low.

So, the Karvonen formula is: ((MHR - RHR) x % intensity) + RHR = Training Zone

Where:
MHR = maximum heart rate (I use 220-age for now)
RHR = resting heart rate
% intensity = desired level of activity (0.6 for 60%, 0.7 for 70%, etc)

The accepted ranges and intensity levels are somewhere near the following:
60% - very light cardio; fewer overall calories, but higher % of fat calories
70% - moderate aerobic
80% - heavy aerobic/interval training
90% - intense (anaerobic); most overall calories, lowest % of fat calories

Although I'm not positive, I believe that the % intensity is not a gauge of fitness level. This confused me for a long time - because many times, it is depicted as such. Beyond that, fitness level is entirely subjective. Rather, % intensity is a gauge of the type of workout you are looking for at the time. Some days, such as long runs, the goal is a lower range; some days, such as when doing speed work, the goal is to extend into the higher range.

So, using the formula above, my numbers turn out to be (32 years old, RHR of 52):
60% - 133
65% - 140
70% - 147
75% - 154
80% - 160
85% - 167
90% - 174
95% - 181
100% - 188

That seems reasonable to me - as I know I can go for long periods of time at a HR of 150 or so, which puts me into the moderate aerobic (definately enough to sweat, but not so much that I wouldn't be able to talk). Also, I know that my endurance plummets when I get into the 170's, which puts me well into the heavy aerobic and even the anaerobic zone.

Also, I recently came across a blog post on triathlontrainingblog.com, where the blogger posted an email exchange between herself and someone who commented on what they were calling 'The Grey Zone'. I normally take 3rd party, unproven data and advice with a heavy grain of salt, but this made a lot of sense, and the person really seemed to know what they were talking about.

In short, the grey zone is too fast for recovery, but too slow for a key run (tempo, interval, etc) - pretty much that 75-80% training zone from above. So if all I did was run at a target HR of 160, I'd be in the grey zone. It's that pace that just feels right because it makes you feel like you worked hard, but not so hard to debilitate you for the rest of the day. The end result is that you do workout after workout, with relatively little performance gain.

That would be why training plans alternate long slow runs with shorter faster runs.

Addendum (9/14): More information on terms, and their explanations.
http://www.heartmonitors.com/exercisetips/heart_rate_basics.htm

Addendum (9/17): (Requires further verification):
60-80% max HR = 1 to 2 min/mile slower than 10k pace
80-90% max HR = 10 to 20 sec/mile slower than 10k pace
95-100% max HR = 3-5K pace
100% max HR = faster then 3-5k pace

Addendum (10/31): Magic Mile Times
10/31/08 - 7:01 Avg HR 179
4/4/09 - 7:25 Avg HR 175
7/3/09 - 7:25 Avg HR 176