Pete Pfitzinger Lactate Threshold Calculator

How is Lactate Threshold Pace Calculated?

In his book, Faster Road Racing, Pete Pfitzinger says the following:

If your experience is mostly with shorter races, LT pace is generally 10 to 15 seconds per mile slower than 10K race pace or 20 to 30 seconds per mile slower than 5K race pace.

There for we can simply calculate Lactate Threshold pace by taking 5km race pace and adding about 15 - 35seconds per mile. This is then converted to min/km as well.

The Lactate thresh hold workout it is possibly one of the most important workouts for runners looking to improve in distances between 8km and Half Marathon. It’s the workout that determines how long you can sustain a more intense effort over a given distance. It’s probably also one of the most misunderstood and confusing workouts for runners.

A common misconception:

“Lactic Acid is the pain you feel, the day after you engage in a strenuous activity.”

This is false, the pain that you feel a day or two after an intense exercise session is Delayed Onset Muscle Soreness (DOMS) which is caused by micro tears in your muscles and actually has very little to do with your Lactate Threshold or Lactic Acid. The only correlation that you could make with a stretch of imagination is that while experiencing DOMS it may be difficult to reach Lactate Threshold pace.

What Is Lactate Threshold?

Lactate Threshold is the pace or effort that you can sustain for a prolonged period of time where the amount of lactate that your muscles are producing can effectively be removed. For most runners this is the fastest pace you can maintain for 1 hour. For Elite Runners this pace is similar to 15km to Half Marathon race pace. For novice runners this pace is closer to 10km pace.

When you engage in a physical activity such as running your body has certain mechanisms to deliver energy to the muscles. This concept applies to most physical activities however in this context I will be speaking mostly with endurance sports in mind, and more specifically running. When you run there are a variety of factors that determine how fast and how long you can run. That’s why when people ask me: ” How can I get better at running” my answer will always be that it depends. It depends on you and what training you have done previously. Runners will always have something that is holding them back stopping them from improving, this could be aerobic efficiency, speed or bio-mechanical efficiency or endurance. By just improving one of those aspects you could improve your overall pace by a significant amount.

Anecdotally my easy run pace was around 06:00min/km for quite a while. It’s something that I track quite religiously and for me it’s the primary indicator of improvement. At the beginning of 2018 I noticed that my easy pace was decreasing (getting faster) quite dramatically and I couldn’t figure out why. Looking back at my training I noticed that the only thing that I had changed was adding strides to the end of a majority of my easy runs. What this had done is increase my bio-mechanical efficiency.

When you run lactate is formed during the metabolism of carbohydrate. During the metabolism of carbohydrate (which is used for energy) pyruvate is formed. Lactate acid is the excess waste product that is left behind after carbohydrate has been metabolized. Your body’s ability to flush out this waste product faster than it’s produced determines how fast your Lactate threshold pace is. As soon as your body can’t keep up with the rate that lactic acid is being formed, you will start to get tired and feel that heavy feeling in your legs.

In your muscle fibers, pyruvate is either used to produce energy aerobically in the mitochondria or converted to produce lactate (the salt of lactic acid). – Pete Pfitzinger

Understanding Lactate Threshold Pace

LT Pace is the upper limit that you can run while producing lactate and effectively flushing it out of your muscles. If you run any faster you won’t be able to sustain that pace for much longer. Your LT Pace is usually the fastest pace you can run at for a solid hour. For Elite runners this is about 15 – 21km. For us mortals, that is closer to 10 – 15km race pace. Another way you can workout your LT Pace according to Pete Pfitzinger’s book – Faster Road Running, is to add about 6 – 9 seconds to your 5km pace. For example if your pace is about 04:00min/km, your LT Pace will be roughly 04:06 – 04:09min/km.

Everyone is different, and your LT pace may be slower, or faster than the method above indicates. This method is strictly a starting point and is not a 100% accurate science. The most accurate way to determine your LT pace is to go to a lab and be tested.