Understanding Heart Rate

So I just got a Garmin, mostly to record long rides on strava without killing my phone battery.

But I'm also a bit interested in the Heart Rate data craze.  So far, everything i've found on heart rate training seems anecdotal at best: "Subtract your age from 220..."  That's about where I stop reading.  It seems like this formula is a good guess, but I just spent $150 on a device that actually measures and records my HR in real time!

Strava's heart rate data for my ride was disappointing at best, i'll explain more in a second

Anyhow, in honor of my new toy I went on a 5 hour mtn bike ride over some pretty challenging terrain.  Strava gave me a disappointing amount of stats on my heart-rate.  Garmin at least tried to calculate zones, and tell me how much time I spent in each zone, but i still don't really get what it means. Or how it calculated the zones in the first place for that matter.  At any-rate, the data is a little weird because it's hard to believe I spent an hour and a half in the highest zone, and 2 hours in an anaerobic state...

Garmin's data was a little more detailed... but still mysterious

So, being a good PhD student, I dug into my Garmin and got the data into matlab. (Trust me: Garmin doesn't make this easy). I then plotted the data into a histogram to look at my heart rate data. A side note: I just binned the heart-rate for each bin, however the Garmin seems to record at non-standard intervals. There were enough data points that I felt this wasn't a huge deal.

Histogram of heart rate data from the garmin. The zones are indicated by red dotted lines and the average heart-rate is indicated by the dotted line.

A couple things to note: The average heart rate does not really show what's going on in the total workout (Although it is interesting to note that there is a peak located right near the average heart rate).  Also, it's hard to tell from the garmin, and impossible to tell from strava, that I spent most of the time on the ride at a heartrate around 166, right on the border of "zones 4" and "5".  This seems to be a good indicator of what my body felt was a hard yet sustainable pace.  The peak around 155 seems to indicate another place my body felt comfortable working at, at a slightly lower pace...

Anyhow, this is just a first dive into heart-rate data for me.  Any training experts have any other advise in looking at their heart-rate data?

  • Erik

    Hey Mike,

    You have put your finger right on the issue with heart rate training; knowing your maximum heart rate. Without this knowledge the training zones gets a bit useless.

    The maximum heart rate can be determined but as you say, a rule of thumb calculation seems a bit anecdotal. The easiest way is to monitor your heart rate for a while and find a good estimation that you can believe.

    Looking at you data it looks like you spent a few minutes at you maximum heart rate 185bpm. I have a hard time believing this since a maximum effort would render you totally winded and in desperate need for a break. My guess is that you max heart rate is higher than 185bpm, depending the level of you effort when logging those high values during your ride.

    If you want to be rigorous this can of course be tested in a lab:

    I am 28 years old and I have logged an all time high of 188bpm while running. I estimate my maximum heart rate to 195bpm. Hoping to do a test this fall to check.

    A note: the maximum heart rate is sport specific (kind of). You won't be able to reach the same values running and riding for instance. On my bike I estimate my max HR to around 185bpm.

    I don't know if I made anything more clear here 🙂

    Good luck with your training. I really miss to ride in the rockies, the season for riding outside will soon be over here.

  • Alan

    Your maximum heart rate is determined by taking a maximal stress test, which is most safely done at your Drs office ;although, you can certainly do it yourself if you don't mind taking the very small risk that you will have a cardiac arrest while doing it. However your maximum heart rate is likely around 195-200, given you probably weren't going 100% to achieve 185 bpm max rate on your ride. The 220-age number is virtually worthless in my opinion as it probably has an std dev of 10bpm across the entire population. I am 55 and currently have a maximum HR of about 195, and it was recorded at 205 on a maximal stress test about 20 years ago.

    Mike, it would be nice if a young energetic PHD student like yourself wrote a little C routine to convert both Garmin gpx and fit files to a Matlab .mat file! That would of course streamline all the ASCII stuff and get it right into Matlab with no fuss!

  • willmcf

    Would love to know how you got that table of time spent in each HR zone out of your Garmin?

    You can test your max HR yourself - have a very good warm up, find a steep-ish hill (10% +) that will take about 2-3 minutes to go up, go relatively hard for the first 2/3rds, but save something in the tank for a sprint finish, then ruin yourself until the the top. You'll get very close to your max.

    • mrsoltys

      That table is straight from the Garmin training center app for mac

      I've heard that test before. It sounds miserable, but also inaccurate. How hard do you ruin yourself? Do you have a friend (or ambulance) waiting for you at the top for when you collapse? In my experience, "ruining" yourself is a combination of a mental limit and a physical limit....

  • Andrew

    I just bumped into this looking for information on getting Garmin's heart rate data onto a histogram. This is something that Polar's software does automatically, and I found it very interesting.

    Part of why I've developed an interest in this lately is that I'm trying to follow a plan based on Joe Friel's book. He argues that maximum heart rate is actually not a very good land mark for heart rate zones, and that lactate threshold is better. You probably bumped into that by accident - I'd speculate that it's that largest spike on your chart, or just to the right. He gives a test for finding it though: Ride as fast as you can for half an hour, and take your average heart rate for the last twenty minutes. Not very pleasant, but maybe not as bad as a max heart rate test.

    • mrsoltys

      I haven't read the book, but it sounds like my intuition and Joe Friel's plan are right on. It's extremely interesting that when you exercise your heart has nominal peaks that it falls into. I'd like to aggregate data over more workouts, but it seems there are at least 3 important peaks in the histogram, and that seems like important zones to consider when training.

  • Greg

    I have been using the Garmin for a couple of years. Mine is a Forerunner 305 model. I get strange readings from time to time and have never been able to pin them down but have a couple of theories. Mine has a chest heart strap - make sure you have it snug and I've learned to dampen it down with water before the workout. Wet your fingers and slide them around between the strap and your chest. Doing this improves the connectivity and readings from the get-go. During your workout, sweat will shortly ensue but I found the early readings sometimes distorted (very high), especially on a steep downhill bike ride.

    The other theory is that there is signal interference which can cause the signal/readings to be off. I ride in rural areas and one area in particular will fairly consistently throw it off. I don't know what frequency this uses but there are electric fences and all kinds of wireless signals around.

    If you want to maximize your heart rate, I suggest doing Peak8 exercise. You are done in less than 20 minutes but it will kick your ass if you do it correctly. There are lots of hits on Google about it and even some Youtube videos. I do it either on a bike and an elliptical every third day. I'm 58 and my highest peak is 170. I suspect I could do better but I workout at an altitude of over 5200 feet. You can do this exercise just about any way you want. There is a 3 minute warmup, eight 2 minute intervals and a 5 min cool down. It's the eight 2 minute part that is where the fun/work comes in. In each interval, you bust your ass for 30 seconds and recover for the remaining 90. Each successive rep your rate rate should be a higher high and a higher low. On the graph it looks like ascending stairs. On the 6th, 7th and 8th rep, you'll be so out of breath, you can barely talk. One bit of advice, don't select the highest level for the exertion part of the rep, knock it down to about 3/4 to maintain speed. Don't worry, you'll get to the max on the easier setting too! On the elliptical, the max is 20. I've tried various settings but have settled on 15. On the low side (recovery), I dial it down to 5. It still varies for me. Some days, I get mid 50's. Most days, I get 60+.