Lactate Threshold

Former marathon record holder Paula Radcliffe could run at 3:15 minutes/km (18.5kph) before her blood lactate rose above normal. What do you think your pace would be?

Given many of my elite idols use lactate testing to inform their training protocols I became interested in the concepts behind it. One can easily make an argument that such marginal gains are of less importance to recreational racers and that is true. Nevertheless, we have the same biology, and understanding it is interesting regardless. Given that formal lab testing is both inconvenient and costly I even bought test equipment and created a test lab in my garage!

Lactate a brief overview

Many still think lactate plays a direct role in fatigue essentially acting as a “poison” to the muscles. This is not strictly true, it is the increase in H+, which is a proton that dissociates from lactate and it is this mechanism that increases the PH. So while lactate itself does not cause fatigue it corresponds to other products in the body that do, and therefore lactate is used as a marker of fatigue. Due to the impact of this acidosis on energy production, there is considerable coaching and scientific focus on delaying this process. Of particular interest is the concept of lactate threshold.

Lactate profiles explained

The chart shows a shift in the lactate curve to the right i.e. the speed/level of exertion at which lactate becomes elevated in the blood is increased. This shift corresponds to increased fitness such that the athlete can perform at higher levels of exertion without accumulating lactate in the musculature.

With training, the body can increase its utilization of lactate and thus maintain muscle function for longer periods before lactate starts to accumulate in the muscles and subsequently becomes elevated in the blood. Increased endurance is therefore associated with an increased lactate threshold. There are two breakpoints or thresholds that we are interested in. The first lactate threshold (LT1) aka Aerobic Threshold (AeT) is the first increase in blood lactate above the resting level, which is typically between 1 and 2 mmol/l. Whereas the second lactate threshold (LT2) aka Anaerobic Threshold (AnT) is defined as the intensity that causes a rapid increase in blood lactate indicating the upper limit of equilibrium between lactate production and clearance. Originally this LT2 maximum lactate steady state was defined as a fixed reading at 4.0 mmol/l but more recent research has shown that this can vary as much as 6 mmol/l between 2.0 and 8.0 across control groups.

Compilation 1 - Step length and duration

Some coaches and sports physiologists recommend that the steps in a lactate performance curve be much longer than the typical 〜5 minutes, especially for endurance athletes. However, longer steps and lengthy test protocols are difficult to perform in the commercial setting. The following example illustrates the potential differences between using short steps and long steps.

A triathlete attempts to estimate her lactate threshold for running by using 7 x 1000 m steps and then compares this test to one in which he uses 4 x 4000 m steps. For many reasons, the 7 x 1000 test is more attractive. The total distance covered is only 7,000 meters versus 16,000 meters so the test is much shorter. There will be 7 data points versus 4 which generally provides a better estimate of the lactate performance curve. However, the chart below clearly shows that the two methods provide very different lactate performance curves. The longer distances are probably providing a much more accurate estimate of her lactate performance curve.

Complication 2 -  Interpreting the data

Another problem with lab results is that the results are presented as absolute values when in fact there are many mathematical interpretation models that when used on the same data set will provide different values.  When looking at the results you need to know that:

• Lactate Threshold values aren’t RIGHT, but they are USEFUL.

• Each interpretation method has its strengths and weaknesses. We need to know them well.

• Pick the right interpretation methods for the chosen protocol and situation.

• What matters above all else is the quality/relevance of the way you plan training based on those interpretations, not the interpretations themselves.

Complication 3 - The anaerobic factor

The traditional way to read a curve as outlined above is that a shift to the right means increased fitness and a shift to the left means deteriorating endurance. The problem with that idea is that it is too simplistic. According to Jan Olbrecht in his book The Science of Winning, two opposing forces mainly act on the lactate curve. These forces are the aerobic and anaerobic capacity. These two factors interact to produce the lactate curve. An increase in anaerobic capacity would shift the curve to the left (meaning more lactate produced at each speed), while an increase in aerobic capacity would shift the curve to the right (meaning less lactate produced). As anaerobic capacity plays a significant role in endurance race performance its improvement should not be neglected. The question then becomes how do we analyze the curve to see if it was a change in aerobic or anaerobic capacity that caused the change? Whereas there is no simple foolproof way Coach Steve Magness recommends the use of an anaerobic capacity test to make things a bit clearer. An anaerobic capacity test consists of running an all-out 400 to 600m and taking lactate readings every 2 to 3 mins afterward until a max reading occurs (typically within 5  to 9 minutes following the test). Combining the maximum lactate number and the speed of your time trial you get a good baseline idea of your anaerobic capacity. When you have this information and the curve from the traditional lactate test you can compare the development of both over time. 

My Conclusions (so far) - the importance of sub-max testing

For recreational athletes, one of the key reasons for testing is because of the importance of pinpointing LT1/AeT Aerobic Threshold. Nailing down this metabolic breakpoint will define the upper end of your Zone 2. Pinpointing LT1 is VERY important as this is your “green zone”. To maximize your aerobic fitness this is where you must spend the majority of your training. As fitness increases this point changes over time and therefore regular testing is required. It is difficult to accurately feel this inflection point.

As LT1 is the most important thing to establish, I recommend a Sub Max test intending to answer the following questions:

• What’s Easy (Z1)?

• What’s Steady (Z2)?

• What’s Moderately Hard (Z3)?

For this, I use  10-minute steps as recommended by Gordo Bryn which progress from Easy Zone 1 to Moderately Hard Zone 3.

1. Start very easy - treat the early part of the test like a warm-up and begin at least ~60 bpm below maximum heart rate.

2. Use 10-minute steps (treadmill) or a distance (at a track) that will take about 10 minutes when running Steady / Zone 2.

3. Use small step heights:

   • If targeting heart rate then increase by 10 bpm per step, or

   • Increase pace by not more than 1 kph per step.

4. Score each step with marks out of 5, half points are allowed, and notice:

   • The transition between Zone 1 (Easy) and Zone 2 (Steady). There will be a feeling of deepening of the breath and pauses in speech.

   • The transition between Zone 2 (Steady) and Zone 3 (Moderately Hard). There will be a feeling of a comfortable work rate and breathing rate is up. At this transition point, there is little physical discomfort and no panting. This is an effort that many athletes incorrectly associate with endurance training pace.

5. Stop the test at a sub-maximal effort, typically 30 bpm below maximum heart rate (HRmax).

The Sub Max Test protocol is not stressful and can be used frequently:

The more stressful Full Profile test can be done to establish the Anaerobic Threshold (AnT) also known as Lactate Threshold 2 and often used interchangeably with the Second Ventilatory Threshold, Anaerobic Threshold, Critical Power, Critical Pace, Maximum Lactate Steady State, Lactate Balance Point. It is enough to know that all these terms roughly define the endurance limit, the effort level, pace, heart rate, and power that an athlete can sustain for 20 minutes to an hour (longer for the well-trained).

That said, I am not fully convinced of the utility of using lactate testing to determine LT2/AnT for my peers.

• It can be hard to find that inflection point in your data.

• Due to the number of test points, it necessitates that the intensity stages are rather short so the effect you are seeing could be transient.

• It can be tough to collect good samples from an athlete at stages of near exhaustion.

Furthermore, I will argue that training intensities above LT1 can be equally (if not better) set by target pacing based on recent race results or time trials.

• Many recreational athletes will do best by aiming the bulk of their “red-zone” intensity at the midpoint between LT1 and LT2, a Tempo effort. This is the race pace for many events and can be set on perceived effort.

• A field test to find LT2 pulse/pace can be a 30-minute maximal time trial.

• An easy way to establish a pace for higher intensity VO2Max efforts is a 6-minute maximal time trial.

Lactate spot testing, when training at these intensities, can be performed to give additional insights. 

Training ideas to improve your lactate curve.

Start with Step 1 (spend a lot of time there) and add in the next steps in moderation to your plan as you progress. The compound benefits of the later steps need to be built on the foundation of the early steps, which is where much of the improvement will come - you can’t just fast forward to the “fun stuff”. 

1. A high volume of basic mileage below LT1 (Zone 1 to Mid Zone 2)

2. Very short high-intensity intervals including strides and hill sprints (Zones 6 and 7)

3. Steady runs at around Marathon Pace (High Zone 2, Low Zone 3)

4. Threshold pace runs - Run around the pace you could race for one hour. Start with 15 mins total and progress to a maximum of 35 to 40 minutes total split into intervals with 2 mins rest between. (Zone 4)

5. Threshold effort runs uphill - Do your threshold intervals on feel, uphill, or on hilly terrain. Works great on a treadmill. (Zone 4)

6. Finally, add the following: (Low to High Zone 5)

   • Medium-length intervals at 10k pace

   • Long Intervals at just slower than 5k pace e.g. 4 x 1600m with 3 min rest

   • Medium Intervals at 3k pace e.g. 3 sets of 4 x 400m with 45-second rest and 3 mins between sets

More information on intensity zones and structuring workouts <HERE>.

If you are curious about testing and live in the Stockholm area please get in touch. As an aging athlete every year I have the challenge of trying to do more with less! Although not essential, I find the insights given by biological markers like lactate testing good inputs into succeeding with that mission.