Last Updated on January 16, 2022 by Heather Hart, ACSM EP, CSCS
You’ve read the posts on why training just below or at your lactate threshold can help improve your overall fitness and running performance. You’ve found tempo and interval workouts to incorporate in your training. There’s only one problem:
How the heck do you know what your lactate threshold actually is?
Great question. There are a number of methods to determine your individual lactate threshold, some more accurate than others. As a coach who works mostly with running clients virtually, I have personally found the 30 minute field test protocol to be the most useful lactate threshold test l for athletes who don’t have access to an exercise science lab.
In this post, we’ll briefly discuss the “why” behind testing, and then explain exactly how to perform the 30 minute filed test, step by step, so you can get a good estimate of your lactate threshold heart rate and pace for training purposes.
Determining Your Running Lactate Threshold
The best and most accurate way to find your lactate threshold – or the point where your body is producing lactate at a rate greater than it can clear lactate from the blood stream – is through a relatively intense test involving blood draws paired with near maximal exercise, performed in an exercise science lab setting.
What is lactate threshold, and why does it matter to runners? Find a more in-depth description and discussion of this topic in the post Tempo Running Workouts for Ultrarunning: Why & How to Add These to Your Training
But the reality is that most of us do not have access to an exercise science lab, or professionals who are trained and capable of administering such tests.
Therefore, the next best solution is to perform a field test.
What is a Lactate Threshold Field Test?
By definition, a field test is a test “carried out in the environment in which a product or device is to be used”. In the case of a running lactate threshold field test, that environment is wherever you would normally run.
Simply put: it’s a test to help determine and estimate your lactate threshold in a natural running setting, outside of a lab.
Why is a Field Test Better than Calculated Estimates?
There are a number of ways to “estimate” your lactate threshold from data you may already have. Some of these include:
Pace estimates: Some say lactate-threshold pace is about 10 to 15 seconds per mile slower than 5K race pace (or about 10K race pace) for slower runners (slower than about 40 minutes for 10K).
The problem with this approach? Not everyone – (especially if we are talking about ultramarathon runners, which make up the majority of this site’s readers) have truly “raced” a 5K or 10K with an all out, 100% effort. Or if they have, those races were long enough ago that they are no longer an accurate depiction of current fitness.
Heart rate estimates: Most experts agree that in general, tempo effort is approximately 75 to 80 % of max heart rate for the majority of athletes.
The problem with this approach? How many runners truly know their max heart rate? Unless you’ve had a lab test done, chances are pretty good that what you think is your max heart rate is just an estimate.
Therefore, the problem with using simple calculations to give us estimates of lactate threshold pace or heart rate, is that we are using estimated data to estimate even more data, with calculations created based on the general population. This leaves a ton of room for error.
While a field test is still not as accurate as a blood test, we are getting a much better picture of what YOU are capable of and how YOUR body reacts, in real time.
My Coaching Preference: the 30 Minute Time Trial
This 30 Minute time trial test comes from cycling and triathlon coach Joe Friel, who debuted this approach in a 2000 article published in Inside Triathlon magazine.
As mentioned at the beginning of this post, as a coach who works mostly with running clients virtually, I have personally found the 30 minute field test protocol to be the most useful lactate threshold test l for athletes who don’t have access to an exercise science lab.
Why? Because the test is simple to execute for my athletes, and when done properly, gives me the data I need to estimate both lactate threshold heart rate and lactate threshold running pace. Even if you don’t work with a coach, the calculations to determine this data is relatively simple.
Is the 30 Minute Time Trial Accurate?
A 2005 study out of the East Carolina University set out to compare four commonly used field testing methods of estimating the lactate threshold of runners: the 30 minute time trial, the VDOT method, the 3,200 meter time trial, and the Conconi Test. In this study, researchers compared the estimated running velocity and heart rate at the lactate threshold determined in each of the four testing methods, to the actual heart rate and running velocity at the lactate threshold determined by blood draws.
The results: researchers found that the estimated running velocity results from the 30 minute time trial and the VDOT method did not significantly differ from the actual measured results of the blood draw test. And in terms of heart rate, the 30-minute time trial estimation was the only one out of the four field tests that did not significantly differ from the blood draw.
Researchers conclude: “These findings suggest that the 30-minute time-trial method should be considered by coaches and distance runners/triathletes as a method for estimating both the running velocity and heart rate at the lactate threshold.” (Source)
Lactate Threshold Test Instructions (30 Minute Time Trial Field Test Protocol)
For this test, you will need a GPS watch that also has heart rate monitoring capabilities.
The 30-minute time trial test should be run all by yourself, without training partners, and not in a race. The reason for this is because you want to run the time trial at YOUR perceived maximal effort, without any influence from other runners.
Further, for pacing purposes and in order to see consistent heart rate data, this test is ideally performed outdoors on a runnable, as flat as possible surface. Trails are not recommended, as the technicality of the trail and subsequent hesitation while finding proper foot placement might slow you down.
Further, treadmills are not recommended because you are not necessarily pushing as hard as YOU can go, and may find yourself running slightly slower or at a lower intensity. But, if you must use a treadmill, make sure you are running at a 1% grade.
(My recommended surface hierarchy for performing this test is first a track, then a flat, open road, then a treadmill, and trails as a last resort. I’m sorry, I know how much we all love trails. )
- Make sure you are well rested. I recommend performing the lactate threshold test the day after a full rest/recovery day.
- On that same note, check the weather. Ideally you don’t do the time trial in extreme cold or heat, as they can affect your performance and your heart rate response.
- Avoid caffeine within 3 hours prior to the test. Caffeine can elevate your heart rate, giving inaccurate data.
- Make sure you are well hydrated and properly fueled – this is a tough workout.
Step 1: Warm up
Run for 10 minutes EASY jog. Do not start GPS timer yet.
Step 2: Begin 30 Minute Time Trial
Once you are thoroughly warmed up, begin your 30 minute time trial. Be sure to start your GPS timer / heart rate monitor at the start of the 30 minute time trial. Then, run as fast/hard but as consistent as possible for 30 minutes. Think: 5K race pace.
Consistency is key here: you want to avoid going out too fast or too hard, and you want to avoid having to walk. What you are hoping to achieve is heart rate data that increases linearly throughout the duration of the run, and peaking towards the end of the 30 minutes. The second half of the test should be as hard, or harder, than the first half. (This is definitely easier said than done!)
Step 3: Hit the Lap Button at 10 Minutes (optional)
If you do not have access to training software compatible with your GPS watch, such as Training Peaks, Final Surge, or Coros Training Hub, then you are going to want to find a way to separate the last twenty minutes of your data from the first ten minutes. The easiest way to do that? Hit the lap button at minute #10 (but keep running!).
And if you do have access to training software, you can skip this step and focus on the run.
Step 4: Stop your GPS & Cool Down.
Once you hit the 30 minute mark, be sure to immediately stop your GPS so that you have a marked end point to your time trial data.
Then, continue on with a cool down run at a recovery pace or a walk. Resist the urge to completely stop, even though you are likely exhausted at this point. A cool down will help lower your heart rate, while helping ward off feelings of dizziness or nausea from the hard effort.
Step 5: Upload & Analyze Your Data
Below is an example of heart rate and pace data from a client’s lactate threshold test. The client in question is a 39 year old male, who I would classify as an intermediate to advanced athlete, with previous ultramarathon and iron distance triathlon experience.
I have specifically highlighted the data I need, which is the average pace and the average heart rate over the last twenty minutes of the 30 minute time trial.
Calculating Lactate Threshold Heart Rate
This is the easy part: your estimated lactate threshold heart rate, or LTHR is the average heart rate of the last 20 minutes of the test. You can see in the data below of this client, while the overall average heart rate for the entire 30 minutes was 160 bpm, the average heart rate for the last 20 minutes was 164 bpm.
Coaches Note: because heart rate monitors – specifically optical, wrist based heart rate monitors – can sometimes give odd readings for a variety of reasons (namely: fit), I will look closely at the graph to see if there are any outlier readings that simply don’t make any sense. For example, if the clients heart rate suddenly dropped from 160 bpm to 70 bpm, with no change in pace (the client didn’t stop running), then I will remove that portion of the data from the average.
Calculating Heart Rate Training Zones
If you’d like to calculate training zones from your lactate threshold heart rate, you can use the following calculations. (I adapted these from the Joe Friel method of determining heart rate training zones.)
Zone 1 Less than 85% of LTHR
Zone 2 85% to 89% of LTHR
Zone 3 90% to 94% of LTHR
Zone 4 95% to 99% of LTHR
Zone 5a 100% to 102% of LTHR
Zone 5b 103% to 106% of LTHR
Zone 5c More than 106% of LTHR
For example, using the client data above, I would do the following calculations:
Average heart rate during the last 20 minuets of the test: 164 bpm
Zone 1 Less than 85% of LTHR (0.85 x 164) = <139 bpm (technically, I calculated 139.4, but for purposes of giving ranges, I round up and down to differentiate zones)
Zone 2 85% to 89% of LTHR (0.85 x 164) to (0.89 x 164) = 140 to 146 bpm
…and so on.
Calculating Lactate Threshold Pace
Estimate your lactate threshold pace takes slightly more work, but it’s not terribly difficult. You can estimate this pace with the following calculation:
Divide the distance covered during the 30 minute test (in meters) by 1,800 seconds (30 minutes).
So again, using our example above, the client ran 4.51 miles in a time of 30:02.
First we need to convert that to metric. You can use an online calculator like this, or you can do the math:
mi X 1,609.344= m
4.51 mi x 1,609.344 = 7,258.141
Since my runner went just over 30 minutes, we’ll be dividing by 1802.
Estimated lactate threshold pace = 7,258.141 meters/1,802 seconds = 4.03 meters per second
But meters per second is kind of useless for us metric avoiding residents of the United states of America. So how do we convert that to miles per hour?
Multiply the rate of meters per second by 2.2369
So, 4.03 m/s x 2.2369 = 9.01 miles per hour.
To convert that to a minute per mile pace, what we are most familiar with:
- Divide 60 by whatever miles per hour (60/9.01 = 6.659)
- Subtract the minutes so that you’re left with just the decimal that represents the number of seconds, and then multiply that decimal amount by 60. … (remove the 6 in 6.659. Multiply 0.659 by 60 = 39.54)
- Add that number back to the minutes, and you have your pace. (6 minutes plus 39.54 seconds, we’ll round up to a 6:40/mile pace)
OR JUST USE A RUNNING PACE CALCULATOR LIKE THIS ONE! (keep it simple!)
Remember – Your Lactate Threshold Can Change
Your lactate threshold (and the heart rate and pace at which it occurs) can change as your fitness status changes. If you improve your fitness, your threshold will most likely increase, and if you lose fitness from a long period of not training or not exercising, your lactate threshold may decrease.
As such, for the most accurate results, it’s recommended that you repeat the lactate threshold test every 4-6 weeks during training.
What do I Do With My Running Lactate Threshold Test Data?
I’m glad you asked! Head over to my post “Tempo Running Workouts for Ultrarunning: Why & How to Add These to Your Training” for a full understanding of how and when to use your lactate threshold heart rate and pacing data in your training…even if you aren’t an ultramarathon runner!
- A quick guide to setting zones. Joe Friel. (2020, April 15). Retrieved January 16, 2022, from https://joefrieltraining.com/a-quick-guide-to-setting-zone/
- McGehee, J. C., Tanner, C. J., & Houmard, J. A. (2005). A comparison of methods for estimating the lactate threshold. Journal of strength and conditioning research, 19(3), 553–558. https://doi.org/10.1519/15444.1
Heather Hart is an ACSM certified Exercise Physiologist, NSCA Certified Strength and Conditioning Specialist (CSCS), UESCA certified Ultrarunning Coach, RRCA certified Running Coach, co-founder of Hart Strength and Endurance Coaching, and creator of this site, Relentless Forward Commotion. She is a mom of two teen boys, and has been running and racing distances of 5K to 100+ miles for over a decade. Heather has been writing and encouraging others to find a love for fitness and movement since 2009.