What Is a Portable Lactate Meter Good For, and How Does It Complement Heart Rate Monitoring?
Ferenc Soma Kovács, Hungarian National Record Holder (Middle Distance)
If you spend any time on social media, you’ve probably seen countless videos of professional and semi-professional athletes taking a small blood sample from themselves before analyzing its lactate concentration with a handheld electronic device. What once looked like something out of science fiction has now become commonplace. Today, even recreational runners can easily purchase portable lactate analyzers and incorporate regular lactate testing into their training.
In this article, I’ll explain why lactate testing is valuable and discuss the most common mistakes beginners make when using these devices.
Lactate threshold is the point at which lactate begins accumulating in the bloodstream faster than the body can remove it. For most athletes, this occurs at approximately 75% of maximal oxygen uptake (VO₂max) and around 85% of maximal heart rate. Put simply, when blood lactate begins to rise sharply, it indicates that you are exercising at an intensity that can only be sustained for a limited period of time.
Within the zone-based polarized training model, two lactate thresholds are generally distinguished: LT1 and LT2.
LT1 represents the metabolic state where lactate production and lactate clearance remain balanced, allowing the intensity to be maintained for relatively long periods. Others define LT1 as the point where blood lactate rises consistently above resting values. On the lactate curve, LT1 typically appears as the first inflection point at approximately 2.0 mmol/L and can largely be considered an indicator of aerobic endurance. Within the familiar five-zone training model, LT1 roughly corresponds to the upper limit of Zone 2.
LT2, on the other hand, lies near the boundary between Zones 3 and 4 and represents the highest intensity that most athletes can sustain for approximately one hour. Traditionally, sports physiologists have associated LT2 with a blood lactate concentration of around 4.0 mmol/L, although in reality this value varies considerably between individuals.
According to polarized training principles, approximately 80% of weekly training volume should be performed below LT1, while the remaining 20% should be completed above LT2. As a result, very little training is performed in the so-called “grey zone” between the two thresholds.
George Brooks’ 1985 Lactate Shuttle Theory overturned the long-held misconception that lactate is merely a harmful by-product of anaerobic metabolism. Brooks demonstrated that so-called producer cells—primarily fast-twitch muscle fibers—transport lactate through the bloodstream to consumer tissues such as the brain, liver, heart, and slow-twitch muscle fibers, where it is used as an important fuel source.
In simple terms, one cell is constantly supplying fuel to another during periods of high metabolic demand.
But how can lactate threshold actually be improved?
LT1 is remarkably trainable.
Large volumes of low-intensity training increase capillary density, mitochondrial content, and the enzymatic capacity of slow-twitch muscle fibers. As a result, these tissues become increasingly efficient at absorbing and utilizing lactate. Over time, the same blood lactate concentration becomes associated with both a higher heart rate and a faster running pace.
When using portable lactate analyzers, however, choosing the device is only part of the equation. Proper blood sampling technique is equally important.
Whenever possible, the earlobe should be preferred over the fingertip. The skin is thinner, blood flow is generally better, and cleaner samples are easier to obtain. Fingertips, by contrast, often develop calluses—especially in athletes who climb, ski, or perform manual work—and they also tend to sweat more. Sweat, alcohol residue, or dirt can easily contaminate the sample and distort the reading.
If fingertip sampling is necessary, especially in cold weather, the hands should first be warmed thoroughly. Cold causes peripheral blood vessels to constrict, making it much harder to obtain an adequate blood drop. Gloves, hand warmers, or even several vigorous arm swings can significantly improve circulation. For some athletes with particularly poor peripheral circulation, the earlobe becomes virtually the only reliable sampling site.
Sampling technique itself also matters.
First, clean the puncture site with an alcohol wipe. After puncturing the skin, wipe away the first drop of blood, as it may still contain alcohol, sweat, or contaminants from the skin surface. The second drop should be used for measurement.
Always approach the blood drop perpendicularly with the test strip, ensuring that only the blood—and not the surrounding skin—comes into contact with the strip. Although this may seem like a minor detail, poor sampling technique is one of the most common reasons for error messages and misleading results.
For this reason, lactate testing begins long before the finger prick itself.
Prepare everything in advance: the lancet, analyzer, test strip, alcohol wipes, and paper towel. Whether measuring beside the track or during a training session, the hood of a car, a bench, or even a large rock can serve as a makeshift table. The important thing is not to rush. In many cases, it is not the analyzer that makes mistakes—it is the sampling procedure.
Most sports watches and training platforms determine training zones using percentages of maximum heart rate. We frequently hear recommendations such as “Zone 2 corresponds to 60–70% of maximum heart rate” or “lactate threshold occurs at approximately 85% of HRmax.”
Reality is considerably more complex.
A 2025 meta-analysis examining data from 412 runners across 25 scientific studies found enormous individual variation in the percentage of maximum heart rate at which both LT1 and LT2 occur—even among athletes of similar fitness levels.
In other words, two runners with exactly the same maximum heart rate may reach the same metabolic threshold at heart rates differing by 15–20 beats per minute.
The reason is simple: maximum heart rate alone tells us very little about aerobic fitness.
Two athletes may share the same HRmax, yet one possesses a much more developed aerobic system, allowing them to maintain low blood lactate concentrations at substantially higher heart rates.
Lactate testing identifies which heart rates correspond to your own metabolic thresholds under specific conditions.
During everyday training, however, these numbers should never be treated as fixed.
Heat, humidity, dehydration, accumulated fatigue, and many other factors can all alter the heart rate associated with a given intensity.
For this reason, heart rate monitoring does not replace lactate testing—it makes lactate testing practical.
Using a Polar sports watch, athletes can continuously monitor heart rate during training and adjust exercise intensity according to current conditions. However, these values should always be interpreted alongside rating of perceived exertion (RPE), running pace, terrain, and—when periodic testing is available—the results of lactate threshold assessments.
The best training decisions therefore come not from relying on a single metric, but from combining all of these sources of information into one complete picture.
Training Insight Supported by Polar
Lactate testing and heart rate monitoring provide different—but complementary—insights into your training. While lactate measurements help identify your physiological thresholds, continuous heart rate monitoring makes it possible to apply those findings during everyday workouts.
If you’re interested in exploring Polar training technology, you can use our partner code at POLARDTC15 for 15% off selected Polar products Polar Hungary