Tuesday, I took another shot at this during a tough workout. Here's what I did:
- 2 mile warm up
- 15 minutes @ LT effort (ave. 6:00 pace; ave. HR 171 bpm)
- 3 minute jog
- 5 x 75 second hills @ 3k effort
- 5 minute jog
- 12 minutes @ LT effort (ave. 6:07 pace into headwind; ave. HR 170 bpm)
- 3 minute cut-down from 3k to mile effort (Max HR 177 bpm)
I decided to consult the internets to find another way to determine my max. I found this very thorough discussion by Sally Edwards where she offers a number of formulas (mostly unreliable), HR max tests as well as submax tests. I decided I'd try the step test. It consists of stepping up and down on an 8" step for 3 minutes using a slow but steady cadence and recording your average heart rate during the last minute of the test. You then add 75 (if you have excellent fitness) to that number to get your max. My HR averaged 107 bpm during the last minute of the test giving me a max. of 182 bpm. I don't think this a reliable value.
At this point, I'm a bit fed up with the quest to determine my max HR. I proposed to my coach that I could just use my HR at LT effort to determine my max, but she pointed out that my LT effort heart rate may actually be quite close to my max. I guess that's why I'm not sure it makes sense to spend much more time trying to figure it out. If I were to go with a max of 182, then I should be running LT effort at an average HR between 160-167 (88-92% of max a la J. Daniels). Based on my recent workouts, I'm pretty sure that LT effort has me between 170-175 bpm and marathon effort/pace around 162-169 bpm. It seems like guessing at a max value is just going to complicate the issue.
I do feel like I gained some useful insight if nothing else from this quest. I looked back at my workouts from 2007, where I actually spent a lot of time running with my HRM strapped to my chest. I was able to see evidence of distinct progress as well as validation of my marathon effort and LT effort heart rates. Back before I ran my first sub-3 hour marathon in April 2007, I did my last long run with 14 miles at goal pace (average pace 6:40-6:55) and happened to wear my HRM. My average heart rate during the goal pace part of the workout was in the 168-171 bpm range. This is close to, albeit slightly higher than, the heart rate range for my marathon-paced workouts right before Twin Cities. However, 2 years later, I was averaging 30+ seconds per mile faster. Progress!
The bottom line for me is that I'm going to wear my HRM more often and not just during easy workouts to keep myself slow. I want more data. My hope is that someday I will see a max value that I can use. If nothing else, I'll have data to geek out on 2 years from now where I can (hopefully) reminisce on how much faster I am running while maintaining an average heart rate of168 bpm.