Lactate Threshold Explained: What It Is and How to Use It in Your Training

If you've ever been told to train "at threshold" without really knowing what that means, you're not alone. While lactate threshold can sound like something only elite athletes need to worry about, in reality, it is one of the most useful measures for anyone who wants to understand how hard they should be training.

Your lactate threshold helps identify where exercise intensity shifts from comfortable and sustainable to increasingly difficult to maintain.

Knowing your lactate threshold can help you set more accurate training zones, pace your sessions better, and understand whether you are actually training at the right intensity.

What Is Lactate Threshold?

Your body is constantly producing and clearing lactate, even at rest.

As exercise gets harder, lactate production increases. At lower intensities, your body can clear it at roughly the same rate as it is produced. As you push harder, that balance begins to change.

This happens across two important points:

• LT1: The first meaningful rise in blood lactate above baseline values.
• LT2: The next significant rise in blood lactate where lactate begins to rise much more sharply.

These thresholds are unique to you and are influenced by factors such as your fitness, training history and the type of exercise you are doing. Measuring blood lactate allows us to see how your body responds as exercise intensity increases.

During a lactate threshold test, your LT1 and LT2 are matched to your heart rate and exercise intensity, turning these physiological markers into practical training guidelines you can use instead of relying on generic heart rate zones calculated from your age or maximum heart rate.

This gives you a much clearer picture of how hard you should be training: how easy your easy sessions should be, where your moderate efforts sit, and when you start crossing into harder, less sustainable work.

How LT1 and LT2 Work

The easiest way to understand LT1 and LT2 is by thinking about how different exercise intensities feel.

Note: These are approximate. LT1 and LT2 do not always fall neatly within standard heart rate zones. Your individual zones largely depend on your physiology.

The relationship between LT1 and LT2 can also tell us more about your aerobic conditioning.

• A wider range between the two generally means you can sustain a broader range of intensities before fatigue starts building rapidly.
• A narrower range can mean exercise starts becoming difficult relatively quickly once you move beyond easier intensities.

A well-developed aerobic system gives you a wider range of intensities to train and race at before fatigue begins accumulating rapidly.

Why Should You Do a Lactate Threshold Test?

By identifying your thresholds and linking them to your actual heart rate, running pace or cycling power, you get:

• Individual training zones: Based on your physiology rather than age-predicted formulas.
• Better pacing targets: Helping you understand what intensity you can realistically sustain.
• A performance benchmark: Allowing you to track how your thresholds change over time.
• Better insight into your current training: Helping identify which areas may be lacking or receiving too much attention.

Your lactate threshold results essentially give you a better answer to one of the most common training questions: how hard should I actually be training?

What to Expect During a Lactate Threshold Test

A lactate threshold test is completed through a series of progressively harder exercise stages.

You will typically:

• Complete a short warm-up.
• Perform several stages on a treadmill, bike or erg.
• Increase your pace or power during each stage.
• Have a small blood sample taken from your fingertip between stages.
• Have your heart rate and pace or power recorded throughout the test.

The test continues until your blood lactate rises sufficiently or you reach your limit. Your results are then plotted on a curve to identify your thresholds.

Not Every Lactate Threshold Test Is Analysed the Same Way

Some methods use a fixed blood lactate value; for example, identifying a threshold whenever someone reaches 4.0 mmol/L.

The problem is that everyone responds differently.

At FORGED by RF, we analyse the pattern of change across your individual lactate curve and cross-check it against your heart rate, pace or power, rather than assuming everyone reaches their threshold at the same lactate concentration.

How to Use Your Heart Rate Zones in Training

At FORGED by RF, we use the Joe Friel heart rate zoning method, which breaks training into Zones 1–4 before further dividing Zone 5 into 5a, 5b and 5c. Your lactate test helps us anchor these zones to your individual physiological response rather than relying solely on generic heart rate calculations.

• Zone 1 – Recovery:
  • Very easy training used for recovery, warm-ups and cool-downs. The goal is to keep the effort low and minimise unnecessary fatigue.
• Zone 2 – Aerobic:
  • Comfortable, conversational training that helps build your aerobic base. A large proportion of endurance training will typically sit here.
• Zone 3 – Tempo:
  • A steady, moderately hard effort. Useful for sustained tempo and race-specific work, but also a zone that can easily be overused.
• Zone 4 – Sub-Threshold:
  • Hard but controlled work as you approach your lactate threshold. Useful for developing your ability to sustain faster efforts for longer.
• Zone 5a – Super-Threshold:
  • The first step above threshold. These efforts are harder to sustain and can be used to develop your ability to work just beyond your threshold.
• Zone 5b – Aerobic Capacity:
  • High-intensity work typically performed in shorter intervals, aimed at developing your aerobic capacity.
• Zone 5c – Anaerobic Capacity:
  • Very short, very hard efforts focused on your highest intensities, speed and anaerobic capacity.

Breaking Zone 5 into 5a, 5b and 5c gives us greater specificity. “Hard” training can mean very different things, and your lactate results help us prescribe those intensities more accurately.

One of the most common training mistakes is spending too much time in the middle: easy days become too hard, while hard days are not specific enough. Knowing your individual zones helps give every session a clearer purpose.

Who Should Consider Lactate Threshold Testing?

Lactate threshold testing can be useful for:

• Endurance athletes wanting more accurate training and pacing zones based on their individual physiology.
• HYROX and hybrid athletes balancing running with high-intensity functional stations.
• Anyone who has plateaued and is unsure whether they are training too hard or too easy.
• Athletes who have completed a training block or are returning to training and want an updated baseline.

The goal is not to collect another set of numbers. The goal is to use those numbers to make better training decisions.

As your fitness improves, you may be able to run faster, cycle at a higher power or produce more output at the same blood lactate concentration.

That is the progress you want to see.

Hear what our client has to say about his Lactate Threshold Test experience with FORGED by RF!

Conclusion

Whether you are preparing for a faster run, an endurance race or your next HYROX, knowing your individual thresholds can help you train with clearer targets and better control of your intensity.

FORGED by RF offers lactate threshold testing in Singapore using individual curve analysis alongside your heart rate, pace or power to establish training zones based on your own physiology.

If you have any questions, please don’t be afraid to contact us via WhatsApp, and our friendly team will get back to you as soon as possible!