Blood Lactate Testing: Protocols for Runners
This guide to blood lactate testing for runners is intended to provide a practical guide to performing lactate testing at home or outdoors, i.e. without the need for a lab. In the interests of brevity and to keep things as simple as possible, we won’t go into the science of what lactate is and how you can train your lactate systems.
These topics are covered in several of our other articles, such as this article on energy system use when running, and this article on how to develop the lactate threshold.
In this guide, we’ll cover:
Reasons for lactate testing
What do I need for a lactate test?
How to take a lactate sample
Importance of pre-test nutrition
Aerobic tests
Anaerobic capacity + clearance test
Interpreting the results
References
Why test lactate?
Testing your lactate levels can provide the following benefits:
It can help set more accurate training intensity zones that are individualised to your unique physiology.
It can help you understand your overall fitness profile and associated strengths and limiters, helping determine what types of training may be most beneficial.
It can help you understand the impact that training has had on your running fitness, allowing you to gain a better understanding of the specific physiological changes that are taking place ‘under the hood’.
What do I need for a lactate test?
Before you begin you’ll want to get hold of the following:
A heart rate strap (ideally a chest or upper-arm strap, rather than one on a running watch, since the latter is unreliable), or a running power meter (e.g. Stryd pod).
If testing outdoors: A GPS-enabled running watch capable of recording pace accurately (or power if using a power meter), and somewhere where you can perform uninterrupted efforts lasting the duration of the test effort (as applicable - see below).
If testing indoors: a treadmill capable of reaching speeds that exceed your threshold pace. Note, most public gyms will not be happy with you taking blood samples, so you will likely need a private treadmill.
A lactate analyser. We recommend the Lactate Pro 2, which we find to be a good analyser for beginners, as it’s easy to use, doesn’t require calibration, gives fewer error readings than other devices, and can be used with very small amounts of blood.
A set of lactate strips that are compatible with the lactate analyser (see below for approximate requirements for each test).
A set of safety lancets. We use these 28 gauge lancets, but if you’re a beginner, you might want to use some with a lower gauge (i.e. bigger diameter), which will help you get a bigger blood drop.
Alcohol swabs.
Some tissues.
A towel.
Something you can use to record your results (e.g. pen and paper or laptop).
Optional (but recommended):
Someone to help take samples.
One pair of disposable gloves for your helper. We recommend avoiding latex gloves, as many people are allergic to these. Nitrile gloves work well.
If testing outdoors, it’s also useful for your helper to be on a bike, so they can stay near you throughout the test and take each sample quickly.
How To Take A Lactate Sample
Lactate samples can be taken either from your finger tip or an earlobe. If you are doing the testing by yourself, you’ll need to take these from your finger.
Below is the protocol we use. By far the biggest reason you’ll get incorrect lactate readings is due to contamination of the blood sample, so most of the steps are concerned with minimising contamination. These steps are important and shouldn’t be skipped.
Get prepared. Before it’s time to take a sample, prepare your equipment by opening the alcohol swab, taking the cap off the lancet (if applicable) and inserting the lactate strip into the lactate analyser. Take care not to touch either end of the lactate strip (neither the chip end that goes into the analyser, nor the testing end that absorbs the blood). This can contaminate the strip and lead to incorrect results.
Once it’s time to take the sample, use a towel to wipe away any sweat from the sampling area (i.e. finger or earlobe) and surrounding area. If you’re a heavy sweater, be generous with the wiping - e.g. do the whole hand, and even the arm and face, as sweat can drip from these areas onto the testing area and contaminate the result.
Wipe the sampling area with an alcohol swab to ensure it’s clean. Allow the finger/earlobe to dry fully before proceeding to the next step. This is important because the alcohol can also contaminate the sample.
Prick the finger or earlobe with a lancet and squeeze out a small drop of blood. If sampling from the finger, it’s best to prick slightly to the side of the finger (rather than right in the middle of the finger pad).
Wipe the initial drop of blood away with a tissue. The first drop of blood will not provide a reliable lactate reading, as it will be contaminated with tissue fluids.
Squeeze out another drop of blood. This will ideally form a nice raised globule a few mm in diameter. If the blood starts running down your finger, wipe this away, and squeeze again to form a droplet.
Very carefully insert the lactate strip into the blood droplet. The lactate strip should just touch the surface of the droplet, and should NOT touch the skin (again, this can cause contamination). You should see the blood soak up the testing strip, and the lactate analyser will probably beep to tell you it’s successfully taken a sample.
Lastly, wait for the analyser to show you your result, and take a note of this.
Extra Tips
In the early stages of testing, blood may not be flowing too well. Try warming up your hands or shaking your arms around before taking a blood sample. This should help to increase blood flow to the fingers. A good tip is to warm your hands in some hot water before beginning the testing.
When squeezing out a blood drop, don’t squeeze too hard. This can increase the content of tissue fluids within the blood drop and will dilute the lactate concentration.
To stabilise the analyser and minimise the risk of the lactate strip touching the skin, your helper can rest their hand or a finger against your hand or head to steady their own hand. If you are taking lactate samples from the finger, you should also rest your own hand on a stable surface, such as the treadmill or handlebars of your helper’s bike.
Always be on the look-out for erroneous lactate values. If you see a big jump in lactate values between stages of the test, it’s best to take a second reading.
If testing indoors, at the end of each stage, you can keep the treadmill running, and jump off the belt onto the panels at the side of the treadmill belt, using the handrails at the side of the treadmill to help. This will allow you to take a sample sooner after the end of each test stage. Make sure you slow the treadmill down before jumping back on, to minimise injury risk.
If testing outdoors, we recommend finding a relatively short, flat, uninterrupted circuit with a good surface (parks are often a good option). If you don’t have a helper, you can then set up your testing equipment at the side of the circuit (i.e. your ‘testing station’). It’s always acceptable to extend the length of any test stages, so if e.g. a stage is 4-mins long, then run around the circuit for 4-mins, and then continue running until you reach the testing station. Another option is to run back and forth on a section of road/good path.
Importance of pre-test nutrition
What you eat before and/or during the test will impact your lactate results. In particular, eating within ~1H before the test can notably impact your test results, and we’d recommend you avoid eating or drinking anything other than water or sugar-free drinks within this 1H window. You should also avoid consuming any calorie-containing foods/drinks during the testing for the same reason.
We’d also advise that you make a note of your nutrition prior to the test, so that you can replicate this as closely as possible before any subsequent tests.
Aerobic Tests
Below are two aerobic lactate test protocols. Protocol 1 allows you to get an overall view of your lactate production rates at a range of intensities, and is useful for getting a high-level view of your physiology and how this is changing over time. However, this test cannot be used to determine your true lactate threshold precisely.
Protocol 2 is for accurately establishing your true lactate threshold - i.e. ‘maximal lactate steady state’ or the point beyond which lactate production exceeds clearance, and lactate levels accumulate rapidly. This can be useful if you want to precisely know your lactate threshold for planning interval training intensities or monitoring changes.
Protocol 1: Full ramp test
Key Details:
Duration: ~1H plus cool-down.
No. of lactate strips required: ~9-13 (more if you need to take repeat measures)
Use this test to determine: Overall lactate profile. Approximate locations of LT1 (also known as aerobic threshold) and LT2 (also known as lactate/anaerobic threshold).
Notes: Recommended for getting an overall view of your lactate profile. Not the best test for determining your lactate threshold (LT2) pace or heart rate.
Protocol:
Begin with a 15-minute warm-up at a very low intensity. The specific starting intensity will depend on your fitness level and estimated lactate threshold, but as a rough indication, you should be starting at no more than 3-4min/mile or 2-2.5 min/km slower than your current best 10km pace, or around 50-55% of your max heart rate. For some people, this might just be a brisk walk. It’s important that this intensity is low so that we don’t miss your first lactate threshold (LT1) by starting too high, so always err on the slower side.
Take a lactate sample 10-14 minutes into this warm-up and record the result and associated heart rate and pace.
Next the ramp test begins in earnest. The protocol is slightly different if testing indoors or outdoors, and if using heart rate, pace or power as your primary intensity metric, as described below:
Indoor Testing
After your warm-up increase the speed of the treadmill by 0.3 kph or 0.2 mph. Hold this pace for 5-minutes, before taking a lactate sample as quickly as possible after finishing this stage. Record running speed and heart rate over the last 60-second of each stage* alongside your lactate reading. If you have a power meter you can record your average power for the 5-min stage in addition to lactate and heart rate.
Start the treadmill up again, and increase the speed by another 0.3 kph or 0.2 mph. Again, hold this pace for 5-mins before taking another lactate sample, and recording running speed and heart rate and/or power as before.
Repeat this process until you record a lactate value that exceeds 8mmol/L or if your heart rate exceeds 95% Max Heart Rate. Once either of these conditions is met, you should stop the test.
If you are a beginner runner, you may want to make smaller speed increments, whereas very experienced runners can make larger speed increments (though smaller increments will allow for more precision, so may still be preferred!).
Outdoor Testing Using Heart Rate
Each test stage lasts 5-mins.
After your warm-up, pick the pace up slightly so as to increase your heart rate by 10bpm.
Allow up to 30-seconds for your heart rate to rise to this level (i.e. don’t make a large and abrupt pace change in order to lift your heart rate quickly). The goal is to build gradually towards holding a consistent pace and heart rate for the remaining 4.5-mins
Take a lactate sample as quickly as possible after finishing each 5-min stage.
Record your running pace and heart rate over the last 60-seconds* of each stage against your lactate reading.
Continue increasing your heart rate and pace in each stage until you record a lactate value that exceeds 8mmol/L or if your heart rate exceeds 95% Max Heart Rate.
We recommend performing the testing on a flat section of good (hard-packed) trail or road, so that you can monitor changes in pace relative to lactate and heart rate. Weather conditions will impact your pace so try to test on relatively consistent days in terms of weather.
Outdoor Testing Using Power
Each test stage lasts 5-mins.
If you have a power meter (e.g. Stryd) and a reliable critical power estimate, you can pace your warm-up using power, aiming for around 60% critical power. Otherwise use running pace and heart rate as described above. In any case, the warm-up effort should feel very easy.
Then begin with the first 5-min stage, increasing your power by around 7% of your critical power (CP) with each stage (e.g. aiming for stages of 67% CP, 74% CP, 81% CP and so on). Don’t worry if you don’t quite hit exactly 5% of your critical power though. The precise jumps in power aren’t critical, as long as they are small enough to identify the lactate turn-points with some precision. If you don’t know your critical power, then use 15-20W increments (higher wattage increments if you are a heavier/faster runner).
Take a lactate sample as quickly as possible after finishing each 5-min stage.
Record your average running power over each stage against your lactate reading. We’d also recommend recording your heart rate over the last 60-seconds* of each stage. This is so that you have data on the relationship between your heart rate and power for times you cannot run with power. It can also help you spot changes in the power you can hold relative to heart rate, which acutely can indicate fatigue or illness, or over the long-term can indicate changing fitness (e.g. holding a higher wattage for a given heart rate reflects improved running fitness).
Continue increasing your power in each stage until you record a lactate value that exceeds 8mmol/L or if your heart rate exceeds 95% Max Heart Rate.
Testing can be performed on any gradient that allows you to maintain a consistent power. Note though that changes in gradient may impact your lactate levels (e.g. a given wattage on a hill may generate more/less lactate than the same wattage on the flat).
*You can record your heart rate throughout the whole test, and then isolate the 60-second average for each stage using analysis platforms like Strava Premium, TrainingPeaks, or Intervals.icu.
Testing Tips
If it’s your (or your helper’s) first time taking lactate samples, take a few extra measures during the warm-up to practice.
We’d recommend repeating any measure where your lactate value has jumped more than 2mmol/L between levels.
If you don’t have a helper and are taking your own lactate samples outdoors, then we recommend setting up a ‘testing station’ (i.e. a table or area where you can lay out all your testing equipment for quick access). For each stage run the full 5-mins, and then continue running at the same heart rate/power until you get to your testing station. Then take your lactate sample as quickly as possible thereafter.
Analysing the results
To get an overview of your lactate profile, plot your heart rate or power (x-axis) against the lactate value (y-axis), as shown. This will help you determine your LT1 and LT2 heart rate/power and thus to set your running training zones and understand your overall fitness profile.
Many labs use fixed lactate values of 2mmol/L and 4mmol/L to determine LT1 and LT2 respectively. However these values are based on population averages, and often aren’t accurate at an individual level. Moreover, these values are highly influenced by things like prior nutrition, fatigue, and time of day. So using fixed cut points can lead to invalid conclusions when assessing changes over time, if these factors aren’t well controlled.
With this ramp test approach, we therefore prefer to interpret the data visually to see:
How high the lactate levels are overall. High lactate levels (e.g. ~2mmol/L or above) in the early stages of the test can indicate poor fat oxidation ability.
What the overall lactate curve looks like. Are there any clear inflection points that can give a rough marker of where LT1 and LT2 may sit.
In the graph above, lactate levels begin at a fairly typical level. We can see inflection points at around 110-120bpm and 150-160bpm, suggesting LT1 and LT2 may sit around these heart rates, although as noted previously, the ramp test is not an accurate method for determining these thresholds.
In subsequent tests, we could then assess whether the overall shape of the graph has shifted. For example is there evidence that the inflection points now occur at a higher heart rate? Or does lactate ramp up less steeply and/or begin at a lower level which might suggest better lactate clearance and/or improved fat oxidation rates? You can also plot your lactate values against pace to see whether lactate values are now lower for a given pace.
Final Notes
You may have done previous lactate tests with shorter stages. However, the results of these tests are less valid, because lactate levels take time to stabilise after each step increase in pace. We therefore would not recommend shortening the stages beyond what is recommended above.
Having long stages is also useful because, if you need to take a repeat blood sample, the results won’t be impacted by this extended break in running, as each stage has sufficient time for the lactate levels to stabilise and will not be impacted to a great extent by the starting lactate value.
Protocol 2: Maximal lactate steady state
Key Details:
Duration: ~40-mins or more
No. of lactate strips required: 4 or more
Use this test to determine: Maximal Lactate Steady State (MLSS)
Notes: Only recommended where precise determination of MLSS is needed. Will need access to a treadmill or running power meter to maintain a very consistent work-rate.
Use Case:
As mentioned, Protocol 1 is good for getting an overview of your lactate profile, but is not appropriate for determining your lactate threshold (i.e. MLSS) precisely. This second protocol is designed to establishing your MLSS with better precision.
Traditionally, MLSS is tested over several days, but we’ve included an adapted version of a 1-day protocol by Palmer et al. (1999).
Protocol:
As mentioned above, for this protocol, you will need access to a treadmill or a running power meter, as it’s important to maintain a consistent work rate within each stage of the test.
You'll also need a good estimate of where your MLSS probably sits in terms of pace or power. You can use information from Protocol 1, alongside field-based testing (such as the threshold heart rate and pace test, or critical power test described here). Your subjective sensations while running can also help. In general, your MLSS will be lower than your threshold pace or critical power.
The idea is to complete one stage at a power or treadmill speed that’s below your MLSS, and then make small increments in power/speed for each successive stage until you exceed your MLSS. As each stage is quite long (11-mins of running), we want to complete the testing in as few stages as possible, which is why we need a good estimate of MLSS before starting.
Warm up for around 15 minutes. In this warm-up your power/treadmill speed should gradually build towards ~80-90% of the power/speed you plan to hold in the first stage of the test. This allows your lactate levels to gradually rise in line with your work rate. If you make a sudden jump from a low work rate to a relatively high work rate at the start of your test, your lactate measure for the first stage may be inaccurate.
Begin with Stage 1, which comprises:
A 3-min steady state effort at around 5% below your estimated MLSS. So for example, if you think that your MLSS is roughly 300W, then you would start at 285W. If you think your MLSS speed is 13.5km/hour, start the test at 12.8km/hour.
A blood lactate sample taken as quickly as possible after this 3-min effort.
An 8-min steady state effort at the same wattage/speed as the 3-min effort.
A second blood lactate sample taken as quickly as possible after this 8-min effort.
Between the first and second sample, lactate should not have increased by more than 1mmol/L, indicating that you’re below your MLSS. If it has increased by more than 1mmol/L, you’re already above your MLSS and have started too hard, and you’ll need to rest for ~10 minutes and start this stage again at a lower power or treadmill speed.
Provided lactate values increase by no more than 1mmol/L during Stage 1, progress to Stage 2.
In Stage 2, complete the same steps as in Stage 1, but increase power/speed by 5% vs Stage 1.
If your lactate has increased by more than 1mmol/L between the first and second samples in Stage 2, this indicates that Stage 2 was above your MLSS, and that your MLSS lies between Stages 1 and 2. You can stop the test here.
If your lactate has not increased by more than 1mmol/L this indicates that Stage 2 was below your MLSS, and you should progress to Stage 3, by completing a further stage at 5% higher speed or power, again taking lactate samples after the 3-min and 8-min efforts.
If your lactate has increased by more than 1mmol/L between the 3-min and 8-min efforts this indicates that Stage 3 was above your MLSS, and that your MLSS lies between Stages 2 and 3. You can stop the test here.
If your lactate has not increased by more than 1mmol/L this indicates that Stage 3 was below your MLSS. If you’re feeling ok, you can continue completing stages with 5% increments as described above, until you hit a stage where lactate values increase by more than 1mmol/L. Else, you can resume testing on another day, beginning at Stage 3.
If you are quite confident in where your MLSS pace/power sits (e.g. from prior recent testing), you can make smaller power/speed increments between stages (e.g. 3% increments).
Testing Tips
If testing outdoors, it’s really important to make sure you keep your power as stable as possible, and we recommend testing on a flat tarmac surface to help with this.
If testing outdoors, this test works best with a helper on a bike who can stay alongside you and take samples as quickly as possible after each effort. If you don’t have a helper, you can use a short (e.g. 200m) circuit to perform the testing, and set up a testing station, as described above. In this case, you would need to extend the 3-min and 8-min efforts, continuing to maintain a consistent power, until you reach your testing station. Maintaining a consistent power is vitally important for this test.
Anaerobic capacity + clearance test
Key Details
Duration: ~30-40 mins.
No. of lactate strips required: 4 or 5
Use this test to determine: VLaMax/glycolytic rate/anaerobic capacity, lactate clearance rate
Notes: If testing on the same day as protocols 1 or 2, this test should follow after rather than before.
Use Case
This test is used as a simplistic assessment of your ability to produce lactate (and thus capacity to generate energy quickly through glycolysis). It is sometimes referred to as anaerobic capacity, or VLaMax. Performing this protocol alongside one of the aerobic tests above can help to give a more full understanding of your fitness profile.
Protocol
After completing one of Protocols 1-2, go straight into 15-mins of easy jogging or walking at around 50-60% Max HR. This will help clear the accumulated lactate from the preceding test. Alternatively you can do the anaerobic capacity and clearance test on another day.
After the 15-mins of easy running, rest completely for around 5-mins, before taking a lactate sample. This should be below 2.5mmol/L. If it isn’t, rest a few more minutes before taking another sample.
Then complete a maximal effort as hard as you can go for 20-sec. We recommend performing this effort on a shallow to moderate gradient to minimise the time taken to accelerate before reaching a maximal effort.
After the effort is complete, stop running entirely. This is very important, as if you keep running (or even walking), this will reduce your lactate readings.
Take samples at 3-mins, 5-mins and 7-mins, remaining at rest throughout. For better accuracy, you can also take samples at 4-mins and 6-mins if you wish, continuing until you see lactate levels drop.
Optionally remain at rest until 20-mins after the 20-sec effort, and take a final lactate sample. This can be used to examine your ability to clear lactate.
Testing Tips
We recommend doing a trial of this test effort on a different day, so you know roughly where you will finish the effort, and can set up your testing equipment, and/or have your helper waiting ready at an appropriate point.
Analysing the Results
The results you get from this anaerobic capacity test might look something like this:
To determine your VLaMax:
Identify the highest lactate level you reached. In the example above, that’s 13.7mmol/L.
Subtract the baseline lactate value (i.e. the lactate value you obtained before beginning the 20-sec effort). So in the example above, 13.7 - 2.0 = 11.7.
Divide by 16S (this is the length of the 20S effort minus the initial 4-seconds of the effort, where energy will predominantly be provided via the creatine phosphate system). This gives you a measure of your maximal lactate building rate or VLaMax. So in the example above, VLaMax = 11.7/16 = 0.7mmol/L/sec.
Alternatively, after you have completed a few tests, you can just compare the maximum lactate value you hit to determine whether your capacity to produce energy via glycolysis is increasing/decreasing.
To determine your lactate clearance rate:
Work out the percentage drop between your highest lactate value, and the lactate value at 20-mins. In this example, lactate dropped from 13.7mmol/L to 4.4mmol/L, which represents a 68% drop. This indicates a strong aerobic capacity.
You can also look at the clearance rate, which is the change in lactate (13.7-4.4 = 9.3mmol/L) divided by the length of clearance (20mins - 5mins = 15mins). Or in other words 9.3/15 = 0.6mmol/L/min.
Notes
This test must be done after the full/abbreviated ramp test not before, otherwise you’ll be waiting a long time for your lactate values to come right back down to baseline before you can begin the ramp/MLSS test.
Maximum attainable lactate values typically range between 15-20mmol/L with some specially trained athletes reaching 25mmol/L. However, it’s also normal to see somewhat lower lactate values in this test, given the effort is very short, e.g. ~5-6mmol/L.
Don’t complete this anaerobic test if you have any health concerns that might be exacerbated by a 20-sec maximal effort, or if you have been advised by a medical professional to avoid high-intensity exercise.
Interpreting The Results
LT1/Aerobic Threshold
Your LT1 gives an indication of your aerobic efficiency. An increase in your LT1 can suggest an improvement in (i) your ability to use fats for energy, (ii) your aerobic capacity (i.e. VO2max) and/or (iii) your lactate shuttling ability.
You can also use your LT1 value to give you an indication of the top of Zone 2 in a seven-zone model.
LT2/Anaerobic Threshold/Lactate Threshold
Your LT2 or Maximal Lactate Steady State (MLSS) is the point at which lactate production equals your maximal rate of lactate clearance.
An increase in your LT2 can suggest an improvement in (i) your ability to use fats for energy, (ii) your aerobic capacity (i.e. VO2max) and/or (iii) your lactate shuttling ability.
You can also use your LT2 value to give you an indication of the middle of Zone 4 in a seven-zone model.
Setting Running Zones
Knowing your LT1 and LT2 heart rate or power can help you to set your running training zones more accurately, rather than relying on ‘standard’ zone definitions (such as the ones described here). We set out some recommended zones below based on LT1 and LT2 power/heart rate:
Anaerobic Capacity/VLaMax
Your highest lactate value after the anaerobic capacity test gives you an indication of your maximal glycolytic rate or VLaMax - that is the maximum rate at which you can break down carbohydrates to produce energy.
An increase in this lactate value would often (though not always) be associated with a decrease in your tendency to use fats for fuel.
If you choose to convert this lactate value directly into a VLaMax value (i.e. in terms of mmol/L/sec), you can get an idea of how strong your anaerobic capacity is. VLaMax typically ranges from around 0.2mmol/L/sec and 1.0mmol/L/sec (Heck et al., 2003). For most endurance sports, it’s been suggested that you’d want this to ideally sit somewhere between 0.3mmol/L/sec and 0.5mmol/L/sec (the lower end for more steady-state types of running e.g. flatter and/or longer races, and the higher end for more punchy types of running e.g. shorter hilly fell and trail races).
However, in our experience, it’s hard to determine VLaMax accurately enough to reliably assess where you sit within these ranges. Plus, the ‘optimum’ VLaMax will also depend on your aerobic capacity (with a higher aerobic capacity allowing higher VLaMax values to be tolerated while still allowing for good endurance and threshold power). Therefore, we do not compare VLaMax values to these standard cut-points, but prefer to use the testing to broadly understand whether VLaMax is either low, medium or high and whether that seems appropriate for the athlete’s goals and other fitness attributes.
It’s worth noting that this testing method assumes that the body doesn’t have time to clear any of the lactate that is produced during the maximal effort. This is not a correct assumption, and the VLaMax value will never be 100% accurate. It will be less accurate for athletes who have a good capacity to clear lactate and a high VO2max with fast VO2 kinetics (i.e. responsiveness of the aerobic system).
Holistic Interpretation
The main value to testing is when you combine all the results of the various tests, allowing you to pinpoint the specific physiological changes that have caused the observed changes in lactate values. We outline some key examples below:
1) LT1 and LT2 power/pace improve, VLaMax decreases
This suggests that the improvement in LT1 and LT2 is probably due to a reduction in glycolysis, and thus an associated improvement in your ability to oxidise fats for fuel. VO2max may have changed, but probably not to a great extent.
2) LT1 and LT2 power/pace improve, VLaMax stays the same
This suggests that the improvement in LT1 and LT2 is probably due to an improvement in aerobic capacity (i.e. VO2max). The rate of glycolysis versus fat oxidation probably has not changed.
3) LT1 and LT2 improve, VLaMax improves
This probably suggests that aerobic capacity (i.e. VO2max) has increased. It’s probable that the rate of glycolysis has also increased, and thus the rate of fat oxidation has reduced. But this is counteracted by the improvement in VO2max, allowing LT1 and LT2 to increase in spite of an increased rate of lactate production.
4) LT1 and LT2 decrease, VLaMax stays the same
This suggests that aerobic capacity (i.e. VO2max) has likely decreased, while the rate of glycolysis versus fat oxidation probably has not changed.
5) LT1 and LT2 decrease, VLaMax increases
This suggests that the decrease in LT1 and LT2 is probably due to an increased rate of glycolysis and associated reduction in the rate of fat oxidation.
Aerobic capacity (i.e. VO2max) might have changed, but probably not to a large degree.
6) LT1 and LT2 decrease, VLaMax decreases
This suggests that aerobic capacity has almost certainly decreased. There might have also been a change in the rate of glycolysis versus fat oxidation, but it’s hard to tell in which direction this might be.
Ad-Hoc Testing
It can also be really informative to perform some ad-hoc testing in order to understand your lactate profile and how this might be changing over time. The world is your oyster when it comes to what you might choose to test! For example, you may wish to test your lactate when running at a particular pace, over a certain type of terrain (e.g. steep, off road etc.), in a specific interval session, over a particular type of race etc. The important things to remember when performing your own ad-hoc testing are:
Any efforts need to last at least 5-minutes so that lactate levels have chance to stabilise at a level that reflects your work rate (if running below LT2).
In order to infer associations between intensity (heart rate, pace or power) and lactate, you should try to hold any efforts at a stable work rate. Running power or treadmill speed is the best way to control this, but heart rate will do if you don’t have access to these, or pace is fine when running on the flat with little wind.
Remember that heart rate also takes time to stabilise, so if you’re looking to examine your relationship between lactate and heart rate, then it’s best to look at your average heart rate towards the end of an effort (e.g. the last 60-seconds).
As an example of some ad-hoc testing, you may wish to monitor changes in your lactate levels when running at a steady 8 min/mile pace over a 5km effort on a flat course. You may take a lactate reading at the end of the 5km effort. A general trend for decreasing lactate levels with training would generally indicate improving running fitness.
Limitations
It’s important to acknowledge the limitations of lactate testing. Lactate monitors are prone to error, particularly if you’re new to lactate testing and/or if you use a lactate monitor that requires large samples of blood or is very sensitive to contamination (e.g. from sweat). This can make interpretation of results hard, because it can be difficult to determine if any measures are erroneous. In our experience, at least three or four rounds of testing are needed in order to confidently understand your lactate profile, and eliminate incorrect readings. Thus, lactate testing is only really valuable if you’re committed to performing this on a fairly regular basis.
Lactate results are also sensitive to numerous factors unrelated to fitness status, such as nutrition, time of day, fatigue, stress, caffeine intake and so on. While you can do your best to control these factors, they will still exert an influence to some degree.
In addition, heart rate is also sensitive to many of these factors. This adds additional uncertainty, particularly if you don’t have access to a power meter or a treadmill to help standardise the pacing of your test efforts.
Your lactate results will also be impacted by the environment you test in. For example running at a given pace or power indoors is quite different from running at the same pace or power outside. Running on the flat is again different from running on an incline. There is a balance between making sure the methods you use to test are relevant to the types of running you do (both in training and racing) vs making sure the test methods are well-controlled and repeatable.
Finally, lactate samples are by no means a perfect measure of what’s going on ‘under the hood’. Lactate is produced at the muscle fibre, and this can then be shuttled to other neighbouring muscle fibres for use as fuel, or transported into the blood stream and then to other parts of the body, where it can be used as fuel or converted back to glycogen. A lactate measure from blood at the fingertip or ear lobe is therefore quite distant from what’s going on metabolically at the working muscle. The measure we see will be influenced by things like total blood volume/body size, how effectively lactate is transported around the body, and how effectively lactate can be metabolised or otherwise cleared, and these factors will differ markedly from person to person. We think that there are better options to lactate testing, such as use of near-infrared spectroscopy to measure muscle oxygen saturation in the muscle capillaries (e.g. using a MOXY device). However, lactate testing remains a relatively cost-effective option and can certainly provide useful insight when better (but more costly/less accessible) options are not available.