Heart Rate Analysis

Completed the dreaded hills interval today, but managed it much better than the last time of a few weeks ago. Worked a shallower incline than the previous two hills sessions, but kept the pace hard. I finally relented on #11, quitting about halfway up the hill. Not sure why I couldn't gut it out. The "quit" came on suddenly and was just a momentary lapse of the will. I made up for it on the last repeat, though I backed off on the pace just a tad.

I was happy to be done, and had time to reflect on what I saw of my heart rate. During the first half dozen, my max HR topped out at around 166 or so. Over the final six, though, I was consistently hitting 169-171 at the end of each quarter, and I could feel it. There's a big difference between 166 and 170 for me.

This got me thinking about what my HRmax really is. I've been working under the assumption that my top end is around 175. But I'm not sure I've every seen my HR get close to that. Thinking back, I think 172 might be the highest I've seen since getting back into running. I derived the 175 figure based on the fact that my 5K/10K race HR seems to be around 158-161, which ought to be around 90% of max. But if 172 is my max, then 158-161 is more like 93%. I don't know what to make of that. Either my lactate threshold is higher (which is possible given my improvements in fitness) or I'm wimping out and not extending myself enough into my top range. I really think that's less likely, but I'm just not sure.

The formula of HRmax = 220-50 would put my rule-of-thumb max at 170. I witnessed a 171 today, so I know that formula isn't defining for me. What about the others?

HRmax = 205.8 − (0.685 × age) results in 171.55. Based on how I felt today hitting 171, that would seem like a better estimate.

HRmax = 206.3 − (0.711 × 50) = 170.75 under shoots me.

The Tanaka formula of HRmax = 208 − (0.7 × 50) = 173.

When I solve all the various formulas using my age "50", they come out to a range of 170-175, so maybe that's close enough. It sure feels like I'm just about topped out at 171, so maybe 172 really is my max after all and not 175. How significant a difference does it make in my training zones?

100% 170 175
95% 162 166
90% 153 158
85% 145 149
80% 136 140
75% 128 131

It sure seems like the 175 right-most column is more characteristic of what I label for my perceived level of exertion, at least up until the 95%+ range. After 166, I level off very quickly. That bugs me. It would seem like maybe I have some more headroom that I ought to be able to access and that I'm just haven't been willing to push on through.

I don't know. Maybe next time I'm working at above threshold training, I'll see if I can access a higher HR than 171...without killing myself, of course.

(I remember watching a young guy in his 20s get on a treadmill next to me, and within a few minutes, he had his heartrate up around 180. I was jealous, though I'm not sure why.