Welcome to Part 3 in my four part series on configuring and using heart rate zones on your GARMIN device!
As I explained in my last post, GARMIN offers three different methods for determining heart rate zones:
- % Maximum Heart Rate (%Max. HR)
- % Heart Rate Reserve (%HRR)
- % Lactate Threshold (%LTHR)
Last week we covered % Heart Rate Reserve. You can find that post here in case you missed it.
Today we will dive into % Lactate Threshold. Let’s get started!
What is Lactate Threshold ???
Well, it’s complicated…
If you’ve been reading my posts for any length of time you’ve probably already realized that I’m an analytically oriented person. However, even I get bored reading about the biological mechanisms behind the concept of Lactate Threshold.
So, instead of reiterating the numerous scientific papers about this topic that can be found on the internet, I suggest it’s easier to think about Lactate Threshold as the maximum Heart Rate you could sustain for an extended time. For example, my GARMIN tells me my Lactate Threshold is 169 bpm. And I know from experience that once my heart rate goes even a little above that number I’m only going to be able to maintain that pace for about 5 to 10 minutes.
So in short, running at or below Lactate Threshold would be sustainable, running above Lactate Threshold will quickly become unsustainable.
Another common way to think about Lactate Threshold is that it would be the equivalent to a runner’s 10K race pace. Most trained runners can keep their heart rate right around their lactate threshold for the duration of a 10k. Distances beyond 10k would require a lower, more aerobic pace.
How is Lactate Threshold determined?
Just use your GARMIN for a week or so. Assuming you have correctly input all of your other stats (age, height, weight, etc.) GARMIN will calculate your lactate threshold automatically and continue to update it as your training progresses.
As with any metric that GARMIN calculates algorithmically it’s important to do your own reality check on this number. For Lactate Threshold you can do this on your next tempo or threshold run. After warming up, gradually increase your pace until your heart rate is near your Lactate Threshold. It probably won’t be fun but can you maintain a pace just below it…? If you go above it do you quickly hit the wall? If so, your Lactate Threshold is probably configured correctly. If not you may need to do some troubleshooting (more on that later).
Note: until recently, autodetection of Lactate Threshold required a chest strap or other external heart rate monitor. However, GARMIN’s most recent software updates have eliminated that requirement and Lactate Threshold detection is now available via the wrist for most current watch models.
Configuring HR Zones with % Lactate Threshold
Similar to % Maximum Heart Rate and % Heart Rate Reserve, the % Lactate Threshold method will calculate your Heart Rate zones as a percentages of the your Lactate Threshold with the following defaults:
- Zone 5 (Maximum) above 100% of Lactate Threshold
- Zone 4 (Threshold) 95-100% of Lactate Threshold
- Zone 3 (Aerobic) 89-95% of Lactate Threshold
- Zone 2 (Easy) 80-89% of Lactate Threshold
- Zone 1 (Warm Up) 65-85% of Lactate Threshold
Now that we have covered all three methods of determining Heart Rate zones let’s compare how using the different methods will result in different zone configurations.
We’ll again use my numbers (Max HR: 183, Resting HR: 42, Lactate Threshold: 170) as an example:
As you can see, for those of us who find it difficult to run slow enough for our Zone 2 workouts, the % Lactate Threshold method of zone configuration would likely result in the highest Zone 2 range of the three options.
Conclusions:
- The %LTHR method of calculating zones will result in the defined range for Zones 1 through 4 being significantly higher than those calculated with the %Max HR and %HRR methods.
- Unlike the %Max HR and %HRR methods, %LTHR does not require an accurately configured maximum heart rate (though you will probably want to know what that number is for other reasons).
- Of the three methods of calculating HR zones %LTHR is the only one that will automatically update on a regular basis and dynamically adjust your HR zones as your fitness progresses.
- With GARMIN’s recent software updates, Lactate Threshold auto detection is reliably accurate and no longer requires a chest strap or other external heart rate monitor.
In my final post of this four part series (coming soon!) I will discuss some best practices for choosing which zone configuration method is best for you as well as some of the nuances you should be aware of when configuring and using heart rate zones with GARMIN.