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What is Lactate Threshold: How to Test & Train

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Lactate threshold, also known as anaerobic threshold due to the absence of oxygen, is the intensity of exercise at which lactate begins to accumulate in the blood at a faster rate than it can be removed.

Any runner, whether a beginner runner or a seasoned runner, knows the feeling: you’re running along, and then suddenly, your legs feel heavy. They burn.

You are pushing harder to run, but your pace gets slower. You fight every urge to stop. It’s at this point you’ve met (and exceeded) what is called the lactate threshold.

Initially seen as a foe, the lactate threshold is actually a runner’s secret weapon: a performance marker to help you become a faster runner.

What is lactate threshold?

Let me first define lactate threshold (LT). Lactate threshold, also known as anaerobic threshold due to the absence of oxygen, is defined “as the intensity of exercise at which lactate begins to accumulate in the blood at a faster rate than it can be removed.”

It is the point during all-out running that your legs begin to burn because your body can’t clear the lactate as fast as it is making it.

Research shows that lactate threshold is at:

  • 50-60 percent of an average person’s VO2 max (the maximum amount of oxygen your body takes in while exercising)
  • 65-80 percent of VO2 max for recreational athletes
  • and 85-95 percent of VO2 max for elite endurance athletes

What is lactate?

In simple terms, lactate is a byproduct of when we burn glucose without the presence of oxygen.

Your body’s mitochondria use glucose to produce energy. What’s leftover from this process is called lactate. For each lactate molecule your body makes, a hydrogen ion is formed.

These hydrogen ions lower the pH level of your blood, making the muscles acidic.

Why does lactate make me run slower?

When running easy, your body has plenty of time to clear the lactate and resulting hydrogen from the blood and recycle it for further energy production. But when you’re running faster, it doesn’t have the ability to do this.

However, lactate isn’t what makes you run slower. After all, lactate is an energy source. The problem arises when your body can’t convert lactate into energy at a faster rate than your body needs energy.

It’s made worse by the presence of hydrogen which raises acidity in your muscles.

Is lactate bad?

Lactate is not the culprit behind your heavy, burning legs and slowing pace. It’s hydrogen. Hydrogen makes you run slower by raising acidity in your muscles.

It’s the hydrogen that makes it hard for your muscles to contract, making running feel more strenuous. The process also irritates the nerve endings of your muscles, producing that burning feeling.

What is the difference between lactate and lactic acid?

Lactate and lactic acid are not the same. Lactic acid is lactate plus hydrogen.

Lactate is produced by your body in response to aerobic exercise, picking up the slack for when your body doesn’t have enough oxygen to keep moving, and serves as fuel for the muscles. When combined with hydrogen, it makes lactic acid.

Lactate was originally pinpointed as the reason for slower running in early research when scientists erroneously drew a connection between muscular fatigue in frogs and the accumulation of lactate and hydrogen (lactic acid).

But remember, it’s the presence of hydrogen that fatigues the muscles.

What is lactate threshold training?

Now, to the good stuff. How can you use lactate threshold to run faster? By using lactate threshold training.

Lactate threshold training is when you run fast enough so that you are just below the level at which your body starts producing more lactate than it can clear.

This can be accomplished with interval training, fartleks or steady-state (tempo) training.

Why is lactate threshold training important?

In short, lactate threshold training makes your body more energy efficient.

By running at lactate threshold, your body increases the number of its energy factories, aka mitochondria, making it more able to process oxygen correlating with less lactic acid accumulation.

When you train at lactate threshold, your body learns how to control its lactic acid production and becomes more efficient at using the energy available to it.

Over time, your body can run faster while consuming less energy. The best way to improve your body’s ability to use lactate for energy is to train at your lactate threshold.

How can I tell what my lactate threshold is?

There are three main ways to determine your lactate threshold:

  1. a blood test
  2. a 30-minute time trial
  3. a race pace calculator like Jack Daniels’ VDOT calculator

What is a Lactate Threshold test?

A lactate threshold test in a laboratory involves a runner running at an easy pace on a treadmill. The pace is gradually increased to the point of failure (crossing over your lactate threshold).

At each intensity increment, a small blood sample is taken from the runner’s fingertips and the level of blood lactate concentration is measured.

What is a running lactate threshold time trial?

Typically, your lactate threshold pace (also known as your running velocity at lactate threshold or vLT) is about the pace you can hold for a one-hour race.

Most runners don’t have the access to do a lactate threshold laboratory test. But runners can still determine their lactate threshold through a running test.

Research has found that a 30-minute time trial on a flat surface on an uninterrupted course estimated vLT just as accurately as a lactate threshold blood test.

How do I do a lactate threshold time trial?

A lactate threshold time trial is simple, accurate, inexpensive, useful, and some may even say FUN. It often gives athletes confidence in their training and themselves!

So, here’s how to do a lactate threshold time trial:

  1. Put on a chest strap heart rate monitor which studies show are more accurate than wrist-based monitors.
  2. Warm-up for 1 to 2 miles. Stop your GPS watch.
  3. Do some dynamic stretching, mobility, drills, and 3-4 strides.
  4. Start a new workout on your GPS watch and run for 30 minutes (by yourself) on a flat surface at a hard, consistent effort. Avoid going too fast. Run at a sustainable “comfortably hard” pace but just below the red line. For most runners, this is at 65-80 percent of your max heart rate.
  5. Stop your watch when done and save your workout.
  6. Cool down for 1-2 miles.

The pace of your time trial is lactate threshold training pace or vLT, give or take 5 to 10 seconds.

How do I improve my lactate threshold?

Your lactate threshold can be improved by running AT your lactate threshold. Most training plans include lots of lactate threshold training at the beginning of a training block. This is because you can’t run faster for longer without your lactate threshold being pushed.

You can improve your lactate threshold over time by making it a regular part of your training schedule. Include in your weekly running a fartlek, steady-state or tempo runs, and lactate threshold interval training one to two times a week.

As you progress, elongate the time running at your lactate threshold rather than running faster. For example, if you did a 20-minute tempo run, run for 25 minutes at your LT pace next time.

Only increase your pace during lactate threshold training when you’ve done a time trial or race to confirm your new faster vLT—which will happen the more you run at lactate threshold!

*Whitney Heins, Founder & Coach at The Mother Runners, talks about how to push that LT.

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