A little over a week ago, I ran in the Anthem 5K. This is a local 5K (3.1 mile) race that I’ve done for several years…this was actually my seventh time. Over the last four years, my times have been nearly the same (within a few seconds). But this year, I was around 45 seconds slower than in the past. At first I wanted to chalk this up to the fact that I have been doing all of my running at an aerobic heart rate for the last three months and a 5K is nearly all anaerobic. Using more fast twitch muscles and forcing my heart to pump a lot faster than it has been is asking a lot. If you are not sure what all of that means, you can read a few of my recent blog posts on What Happens When We Exercise (Part 1 and 2). But once I got a chance to look at my heart rate data from this last 5K, I noticed something.

My maximum heart rate during the race this year was only 179 beats per minute. While this is pretty high, it’s not nearly as high as I’ve seen it in the past. My max HR was 193 for the 2014 5K and 185 for the race in 2013. So this got me thinking – what is my actual maximum heart rate. There are several methods out there to calculate max heart rate without ever running a step. The most popular is the Age Adjusted method (220 minus your age for men and 226 minus your age for women). I’ll be 37 in a month, so for me, this works out to be 220-37 = 183 bpm. Other methods are the Londeree and Moeschberger (206.3 – 0.711 x age) [179.99 bpm] and the Miller Method (217 x 0.85 x age) [185.5 bpm]. These last two are the same for both  men and women. So based on the formulas, my max heart rate should be somewhere in the low 180’s.

Of course, we all know that “calculations” are not as meaningful as real world data. The methods that I outline above tell me that I should not physically be able to get my heart to beat more than 185 or so beats per minute…yet I have race and training data showing me hitting upwards of 190 bpm several times in the last few years. I think that heart rate calculations can be valuable to give you an idea as to where to set training zones and how to structure heart-rate based workouts, but they are definitely not as accurate as doing a test or looking at data from a race.

Max Heart Rate is like running in the red…you can’t hold it for very long!

So back to my recent 5K. Why was my time so much slower? I think it’s pretty obvious when I look at my heart rate data from the race. I just wasn’t able to push myself to run fast enough. If my max heart rate from the race had been similar to that of previous years, then I could reasonably assume that my training is just not up to par. But the fact is, I didn’t have the ability to push myself through the pain this year. When my heart rate and pace became uncomfortable, my brain told me to ease up…and I did. I’ve been able to block this out in the past and get to the higher heart rate and speed. I know what it feels like. I’ve come close to blacking out after hard intervals on the track and bike trainer. It’s a feeling that you don’t forget!

2104 Anthem 5K Data

2015 Anthem 5K Data

So in just comparing this year with last year, you can see that not only was my peak heart rate higher last year, I was also able to spend over 15 minutes (not consecutive) above Threshold in 2014 and less than 2 minutes in this very uncomfortable zone in the 2015 race. It’s hard to push your body to this place, but due to the way I plan to train for Ironman again this year, I will need to figure out a way get my body into this zone more often.

In reality, you really don’t need a heart rate monitor or training zones to know what constitutes a hard interval versus an easy recovery run. But it is important to know about how heart rate zones work and the physiology behind what’s going on as you train and race at various intensities.

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