FTP (functional threshold power) is an integral part of training for cyclists. Unlike the subjective nature of heart rate training, power is a truly objective measurement of the effort a cyclist is putting out. While most cyclists are aware of the basic principles of power and how to use it (or at least how to compare their numbers to others) there are some fundamental changes that ought to be made in the way we think about FTP and how it is assessed. If you train with power, you’ve undoubtedly done a power test to determine your FTP. There a number of tests that claim to accurately calculate FTP and once you have your number you’ve also undoubtedly plugged it into some calculator to determine your training zones, be it Strava, Training Peaks, Garmin Connect, or manually worked out with a calculator. But what actually is FTP and what does it signify? When Hunter Allen and Andy Coggan released the seminal book on training with power Training and Racing with Power, they defined FTP as the amount of wattage a cyclist could sustain for 60 minutes. Because most cyclists don’t have the patience or the focus, they claim, to do an all out one hour test, they concocted a 20 minute test that could be used to estimate your 60 min power value. Since then a number of other coaches and training centres have developed different tests that come up with basically the same number but using different testing protocols. But how much stock should we put into FTP as a measure of 60 min power and how much should we rely on tests to give us an accurate reading of our FTP?
The classic FTP test is the one prescribed by Allen and Coggan, which is a one hour ride consisting of a warm up, a 5 minute all out VO2 effort and finally the 20 minute all out effort. At the end of this test, a rider takes the power produced during the 20 minute effort and multiplies it by 0.95 to determine FTP or theoretical 60 minute power.
Carmichael Training Systems came up with their own power test using two back-to-back 8 minute power tests, in which the power produced in each 8 minute segment was averaged then multiplied by 0.9.
These are the two main power tests that most cyclists use –although there are others. The inherent problem with these tests is one that many cyclists and coaches have noticed and observed: most cyclists cannot ride their tested FTP for one hour. Many can come to do so with training but for the most part very few cyclists, with the exception of strong time trialists can ride their determined FTP value right out of the gate.
The guys over at power2max realized this and created a calculation using a combination of 5 minute power and 20 minute power to determine true FTP (i.e. what you can actually sustain for 60 minutes). If your ego is somewhat fragile, I highly recommend avoiding this calculation as it will give you an FTP much lower (likely 30-50 watts lower) than what you are currently sitting at.
FTP vs 60 Minute Power
Is it that important to know what your true 60 minute power output is? The simple answer is no and and argument could be made that we need to decouple FTP from 60 minute power and make FTP its own stand alone metric. The reason for this is simple, the training zones, which we use to develop workouts and intervals, are based on the FTP number obtained using one of the above testing protocols, not the the true 60 minute power. Rather than think of FTP as our 60 minute power, we ought to simply use FTP as a metric to calculate training zones and gauge relative increases in fitness over time. It may be the case that with a strong endurance training program, athletes will start to see their real 60 minute power values come up to their tested FTP but for the sake of practical application, it isn’t necessary to be able to actually ride for 60 minutes at FTP in most cases. It is only important that the testing protocol be consistent and that the training zones determined using the the value determined from said protocol sync up correctly.
For the most part the training zones developed by Allen and Coggan sync up with their testing protocol for most athletes. Zones based on percentages of FTP, however, do not account for individual athletic ability. For example, an athlete with a well trained or natural ability to sustain high power outputs for 5 minutes might find that their zone 5 power range is too easy when based on their FTP which may be relatively weaker than their 5 minute power. Such athletes would likely benefit from CTS’s two 8 minute test rather than the standard 20 minute test. This may give them a higher FTP value which would put their zone 5 range closer to their actual VO2 max ability but may make tempo riding (or zone 3) more difficult. Conversely, an athlete with a well developed aerobic engine but lacking in top end power might find that their anaerobic threshold determined from their FTP (the beginning of zone 6) might be more than what they can sustain for the typical duration of an anaerobic interval. Sometimes these variations are evident in different periods of training. Athletes in their final build phases might find themselves producing more top end power than what their power zones would predict for that particular duration of time. Individualization of power zones can be difficult to do accurately but a skilled coach with access to enough power data can develop such zones to maximize training efficiency and adaptation. Unfortunately there is no hard and fast way to create or determine such zones, which is why it is important for coaches and athletes to have a wide range of power data to be able to best estimate individualized power zones.
Where do we go from here?
Ultimately FTP will remain the gold standard for developing training zones but there is still room for refinement in how it is determined and used. The training zones are designed to match up with different types of energy production. Zone 2 is typically thought to be the endurance zone, wherein an athlete is using almost entirely fat for fuel while zone 6 is predominately a glycogen driven effort and FTP being the threshold at which fat metabolization starts to be overwhelmed by the effort produced. Individual strengths and weaknesses of course don’t alway match up perfectly with a generalized system and sometimes athletes find themselves being able to produce more or less power for the typical interval length of each zone (3-8minutes for Vo2 max efforts, 20-60minutes for threshold efforts, 1-2 minutes for anaerobic efforts). It’s important for athletes to massage or manipulate their training zones and testing protocols to best suit their individual goals and their sport. If your goal is to improve Vo2 and top end capacity, a test that best reflects your Vo2 ability like the CTS 8 minute test may produce an FTP that generates training zones better matched to your top end abilities than a standard 20 minute test would. There is no perfect system but with careful analysis of power data it is possible to refine your training zones to be more effective and produce better results.