Everything You Think You Know About LTHR is Wrong


A common question from those concerned about maximising the benefits from their training is how best to set up heart rate training zones based on Lactate Threshold Heart Rate (LTHR)

What is LTHR and How do you Use it?

First let's define what exactly Lactate Threshold Heart Rate is, and why it is useful. If you were to do a sustained, maximal, one-hour effort your average heart rate during that effort is your LTHR. Just like maximum heart rate, LTHR can vary widely from person to person. Knowing your particular LTHR is vital if you want to get the most benefit out of your workouts. The key to maximising your training is to make sure you are Suffering at the correct intensities for the correct amount of time. Knowing your LTHR will allow you to tailor your training zones to your specific heart rate and maximise your Return on Suffering.  

The Old Way of Calculating LTHR

Enough digital ink has been spilled on the “correct” way to measure LTHR to fill the crater of Mt. Sufferlandria. The old, traditional method is to take your average heart rate for the last 20 minutes of a 30 minute all-out effort, or alternatively, your average heart rate for a 20 minute max effort. This value would then be used to set up your training zones. At The Sufferfest Sports Science Division we feel there are some downsides to using this method. The main issue is that your heart rate during a 20 or 30 minute all-out effort will give you a higher heart rate than you could hold for an hour long effort. That’s like saying, “I can average 1,000 watts for a 10-second sprint, so I should be able to average 1,000 watts for 10 minutes.” While optimistic, this isn’t realistic. Let’s look at why.  

Physiologically when you ride at intensities above your FTP your body starts releasing stress hormones, such as norepinephrine and epinephrine (commonly referred to as adrenaline). Your heart rate increases in response to the epinephrine in your blood. As the levels of epinephrine rise so will your heart rate. That is why it is tricky to base your LTHR off of a test where your average effort is greater than FTP. All that epinephrine is muddling the results, making it seem like your LTHR is higher than it actually is.  

Our observations and empirical studies at Wahoo Sports Science have led us to believe that there is a better, more effective way to calculate LTHR and use it to determine the appropriate training zones to give you the greatest Return on Suffering.  

How We Determine LTHR

If you have a full hour to do a maximal effort, you certainly have that option. Just make sure you don’t have anything strenuous to do for the next two days. Like walking. There is, however, a quicker way. It’s not going to be pretty, but it will get the job done. It’s time for some full exposure.

The aptly named Full Frontal is a Sufferfest fitness (ahem) “examination”, a workout designed specifically to help you determine your comprehensive Four-Dimensional Power™ profile and your LTHR. 

A few words of advice before you expose yourself to Full Frontal. The key is not to go too hard too early. The more evenly paced you can complete each effort, the more accurate your LTHR will be. Perfect pacing can take time to master, so don’t fret if you struggle with your pacing during your first few cracks at Full Frontal. For more information on how to get the most out of Full Frontal, read this.

If you have your heart rate monitor connected to The Sufferfest app during the workout the app will take care of calculating LTHR for you, and then set heart rate zones for all subsequent workouts based on that value. The app calculates the highest 20-minute average heart rate for the test and subtracts 2%

How We Developed a New Way of Calculating LTHR

The Sufferfest philosophy of LTHR and training zones is based off of our Head of Sports Science, Neal Henderson’s years of experience as the head of Sports Science at The Boulder Center for Sports Medicine (BCSM). During his tenure he performed over 10,000 physiological tests in the lab. By comparing the results of these tests with data collected from athletes in the field, he was able to refine the testing protocol to create a new, more accurate method. It’s important to note that everyone’s heart rate will respond differently to the same workload, and no one method for calculating training zones will be universally applicable or yield results that are 100% accurate for every single individual.

If you have previously set up LTHR based on your average heart rate from a 20 or 30 minute test it is likely that the LTHR you get by using our method will be a little bit lower. But don’t worry. Despite the change, you haven’t gotten slower. You’re training has only gotten more effective.

Keep in mind that your heart rate can vary quite a bit from day to day. Things like hydration, fatigue, and stress can have a profound effect on heart rate. That is why when determining how hard to go during a given effort it’s best to combine heart rate with RPE (and power data if you have the ability to measure it through a power meter of via simulated Virtual Watts).

By comparing multiple factors like heart rate and RPE you can adjust efforts accordingly. You will also want to ensure your Torture Chamber has adequate cooling by using a good fan. Your body produces a lot of heat when exercising, and if you start to overheat your body responds by diverting some blood closer to the surface of your skin where it can be more readily cooled. Your legs still need the same amount of blood, though, so the only way your body can simultaneously provide blood to your legs and divert it to the surface of your skin is by increasing your heart rate. This can cause of what is called “heart rate drift”, which is when your heart rate rises above your LTHR despite the fact you are doing an effort under your FTP.

If you’ve used the old standard method of determining LTHR you might feel that this new method results in an LTHR that is “too low”, meaning that longer efforts—particularly sustained climbs like those in Hell Hath No Fury and Thin Air— are now “too easy”. Physiologically speaking, a sub-threshold effort gives your body 99% of the same training stimulus as a full on threshold effort. However, the total stress on your body is higher after threshold efforts compared to sub-threshold efforts. In practical terms this means if you’re using the heart rate zones based on The Sufferfest LTHR method as part of a complete training plan, going “easier” isn’t necessarily a bad thing. In fact, quite the contrary. Staying right below threshold will leave you fresher to smash tomorrow’s workout.  Hitting two workouts back to back is a much better training stimulus than hitting day one at full gas but falling apart on day two.  If you aren’t as concerned with being fresh the next day, then by all means, see what the weather’s like up there above your LTHR and Suffer like there’s no tomorrow. You won’t hear the Minions complain.

About Coach Mac Cassin

Mac Cassin has been coached by Sir Neal Henderson since 2009 and is Head Cycling Physiologist at Wahoo Sports Science, with a focus on masters and junior racers. As an elite cyclist who also has to balance the demands of ‘life’ with his goals as an athlete, Mac has a deep understanding of how to get the most out of those who have limited time to train. Mac has raced at the World and PanAmerican championships and holds several US national and state titles. His studies were in Integrative Physiology from the University of Colorado and has worked as a research assistant in the CU Neurophysiology lab.

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