The most accurate way to measure lactate threshold
The gold standard of lactate threshold measurements requires you to either be in a lab, or to work out hard and take regular blood pin pricks in order to measure the lactate in your blood and record when it starts rising fast.
For those of us who don't own watches with the blood sampling feature, there are a few other more accessible ways to get a good idea of your lactate threshold.
Calculate lactate threshold via the 30 minute field test
This is a pretty simple, if tough way to get a really good idea of your lactate threshold.
Requirements: running watch with HR monitor or chest strap, place to run hard for 30 minutes.
Do a comfortable warm up for around 10 minutes. An easy jog combined with simple drills to make sure you're ready to work hard.
Run hard for 10 minutes, pacing as though you'll run that hard pace for 30 minutes.
After that initial 10 minutes, lap your watch and continue running hard for another 20 minutes. This should give you 30 minutes of hard running total, excluding the warm up.
Once you're done and have your breath back, look at the average heart rate for the latter 20 minutes of the 30 minutes hard running, excluding the first 10 minutes of hard running.
This average heart rate and effort level is a really good indication of your lactate threshold.
Essentially, if a running effort increases your heart rate beyond that figure, we can assume that lactate will also begin accumulating in your system faster than your body can clear it. Otherwise known as your lactate threshold.
You can learn more about how your running watch calculates lactate threshold here.
Calculate lactate threshold using an online calculator.
There are various online lactate threshold calculators that can give you an idea of your threshold.
Most of them (including mine, linked above), take a recent race effort as a proxy for recent, hard effort, and using some maths and historical data, give you back your lactate threshold heart rate. The HR at which going beyond, means lactate accumulates in your blood faster than you can clear it.
Calculate lactate threshold on a running watch.
Running watches can give you an estimate of your lactate threshold by simply assessing your pace and heart rate data. Once your watch notices a trend in your data, maybe that when you run over a certain heart rate, you always slow down after a certain amount of time. Over time, your watch can get a good idea of the pace and heart rate that you normally only sustain for certain periods of time.
Learn more about your running watch's lactate threshold.