Understanding and Applying FTP and Lactate Threshold

Before I get too far into this post, I think it will be important to define FTP (Functional Threshold Power) and Lactate Threshold.

Functional Threshold Power – The amount of watts someone can sustain for one hour of maximal intensity

Lactate Threshold – The rate that the body can’t remove lactate from the blood faster than it’s producing it.  The number that exercise scientists agree upon is 4 mmol/l.



The big question is, are these terms interchangeable?  The answer is yes… and no.  It depends on someones level of fitness and their ability to push themselves through the discomfort.  For the untrained individual, they won’t have the cardiovascular or muscular fitness to sustain a effort at lactate threshold (LT) for the full hour.  But for trained athletes, the numbers for wattage produced on the bike at LT and FTP should be very close.  So the sake of the article, I’m going to treat the answer to the question as yes.

The next big question is how to determine FTP/LT.  If you have a powermeter on your bike, you can look at some race data which you were going all out for an hour.  That way is the most accurate.  However, there are other ways of figuring it out:

1.  Step test – this test can be done on your own or with someone checking lactate levels.  It will be more accurate if you can have lactate levels checked, but a rough estimate can be done just by noting your breathing rate and intensity.  This test should be done on trainer that has the ability to increase wattage at specific increments.  (I suggest 25 watt steps.)  Start the watts on the trainer about 150-175 watts less than what you think your FTP/LT is going to be.  After getting warmed up, start the test and increase the watts and/or checking blood lactate levels every 2 minutes.  When you reach your FTP/LT you will notice your breathing changing from labored to “huffing and puffing.”  This is your body trying to blow off the excess hydrogen ions in your blood from the lactate acid making the pH of the blood too acidic.  When this happens, you know that your FTP/LT is somewhere between the current wattage and the previous one.  Without blood lactate levels being drawn, some guess work on your part will need to be done based the rate of perceived exertion (RPE) on the last step before the breathing changed.  If lactate levels are being drawn and recorded, the computer can estimate where LT/FTP is based on the curve of the line.

2.  20 minute Critical Power (CP) – This again should be done a trainer.  The trainer should have the ability to measure average power or a powermeter on the bike will be needed.  This test is simple and just requires the rider to go all out for 20 minutes (don’t accelerate at the end… and you should be completely spent).  Once that is done, multiply the power you have for the 20 minute average by 0.95 and you have FTP.

There are several other ways to determine FTP/LT but these two seem to be the easiest.  Of course, if you don’t have a powermeter on your bike or a computrainer, or another trainer with abilities to measure watts, be sure to wear your heart rate monitor.  It’s not as accurate (several things influence HR) but it is much more affordable than a powermeter.

So, great, you now have the ability to determine your FTP/LT… but what do those numbers mean and how do use them?

The first thing you must do is set your training zones.  I personally like Andrew Coggan’s method of setting up training zones:


Coggan’s Power Training Levels

Active Recovery: <55%  FTP or <68% or HR at LT

Endurance:  55-75% FTP or 69-83% of HR at LT

Tempo: 76-90% FTP or 84-94% of HR at LT

Lactate Threshold: 91-105% FTP or 95-105% of HR at LT


VO2max: 106-120% FTP  (3-8 minute interval pace) or > 106% of HR at LT

Anaerobic: 121%+ FTP (HR n/a)

Neuromuscular: >1000w? (HR n/a)



Now that we know our  training zones, how do we increase our FTP and/or power at LT?  As you  can see from the pictures above, the most benefit we get in raising our FTP or power at LT is to train in zones 3 and 4.  It’s important not to neglect the other zones though.  Recovery is needed to be able to the desired intensities the next day.  Endurance (zone 2) teaches the body to resist fatigue.  Zones 5 and 6, although not used much in longer races such as 70.3 and 140.6 still need to be visited occasionally to  increase stroke volume of the heart, and give us the snap we need to pass someone to avoid a drafting penalty or climbing a short hill to power over it and continue our speed.

Now… the last big question that I’m sure you’re asking:  What percentage of FTP should I race at in my triathlons.  Here are suggested ranges (these ranges are for age group athletes, pros tend to race at a slightly higher wattage.  These percentages also don’t take into account fatigue resistance/rate):

Sprint distance: 95–100%

Olympic distance: 85–95%

Half-Ironman (70.3):  75–85%

Ironman: 65–75%

I’ve told several people this and will say it again:  If your serious about getting faster, the best thing you can do is purchase a powermeter. (my personal choice would be a crank based one so you can race and train with it, such as the SRAM Quarq.)  Forget the areo/race wheels.  Save those for your next big purchase.