Functional Threshold Power (FTP) was developed by Dr. Andrew Coggan and is specifically defined as “the highest power a rider can maintain in a quasi-steady state without fatiguing. It is an estimate of the power output that corresponds most closely with the maximal metabolic steady state or metabolic control limit, or what is more commonly referred to as threshold.” (See Training and Racing with a Power Meter, by Andrew Coggan.)
In the last several years, many other authors and publications in the media have taken their views on what FTP means, resulting in various definitions. More and more phisiology experts, coaches and athletes are opting for other methods of determining their threshold and training zones, as FTP has many limitations.
FTP is a training tool. It is perhaps the most popular training tool because it is relatively simple to determine by any athlete on their own. One way to train with purpose to get fitter and faster on the bike overtime is to know your FTP or a similar measurement to determine your training zones. Coaches usually design workouts by using power zones as a percentage of your FTP or by prescribing intervals to be done at specific target watts for a certain duration.
There are several ways to measure FTP through riding, indoors or outdoors. These are typically referred to as “FTP tests”.
The most popular and commonly used test is the 20-minute time trial, with the goal of producing the highest average power possible over this period. The FTP will be 95% of the average power produced over the 20-minute period. For example, if your average power for the 20 minute effort was 100 watts, your FTP is 95 watts (100w x 95%). Why 95%? Because “in theory”, if you can ride at 100w for 20 minutes, you should be able to ride for 95w for 60 minutes.
However, many scientists agree that this methodology tends to result in an FTP number that is higher than the actual number an athlete would actually be able to sustain for 60 minutes. Athletes are therefore advised to be careful with potential overtraining, fatigue and injuries that might result from using an FTP from the popular 20-minute test.
Further, Dr. Stephen Seiler, one of the most respected authorities in exercise physiology, says that a 60-minute time trial is a more recommended and realistic way to determine an athlete’s threshold.
There are other ways to measure your FTP, and the science of performance is quickly evolving. Take a listen to this Fast Talk podcast on the reasons why FTP might not be the “end all, be all” measurement for training.
The frequency of testing should be coordinated with your coach. In the early stages of development, testing every three months is quite satisfying because improvements can be quite large. Over time, and if you are a more seasoned athlete, FTP growth will slow making the test frustrating at times. I personally like to use other tools, such as WKO4 software, to adjust athletes’ FTP as needed over time, without the need to put them through a 20 or 60-minute test.
A convenient option is to perform an FTP test on Zwift by selecting any of the two available workouts, described below. Both use the 20-minute test approach discussed above. Upon saving your ride, you will be notified of your FTP.
The standard test on Zwift starts with a 20-minute ramp that goes from 30% to 70% of FTP. Next is 3 sets of 3 intervals, each for 20 seconds at 90%, 110%, and 130% of FTP (9 minutes total), followed by 5 minutes at 60%, 5 minutes at 110% and 10 minutes at 60% of FTP. Then the test starts with a 20-minute block where you ride as hard as you can sustain for that duration. Cool down for 10 minutes.
This version of the test has a shorter warm up. It starts with a 5-minute ramp going from 30% to 70% of FTP. The next set is 3 intervals of 20 seconds each at 90%, 110%, and 130% of FTP, followed by 3 minutes at 60%, 3 minutes at 110%, 2 minutes at 120%, and 6 minutes at 55% of FTP. Then the test starts with a 20 minute block where you ride as hard as you can sustain for that duration. Cool down for 5 minutes.