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Day 29 – Functional Threshold Test

145 Days until IRONMAN 70.3 Chattanooga

Christmas Eve day started out with everybody’s favorite indoor bike ride: the FTP test. If you’re not familiar with it, let me tell you all about it.

Functional Threshold

A long long time ago in a laboratory far far away, the idea of training thresholds was born. Dr. Andrew Coggan is perhaps the most recognized authority on this subject and he has written many articles on it. One such article is here on TrainingPeaks. The overall idea is that athletes need to train at certain levels (of heart rate, power, pace) depending on their needs and those levels are unique to each athlete. The way to establish the levels, called zones, is to establish a benchmark which happens to be tied to a physiological phenomenon called lactate threshold.

Power Tap wheel hub

Power Tap hub on rear bike wheel

So Coggan tells us that our benchmark can be found by performing our sport (cycling or running) for an hour at maximal sustainable intensity. From that we can approximate threshold heart rate or power (using a power meter on the bike).

But doing that for an hour requires superhuman mental toughness to stay focused and maintain sustainable intensity. Therefore, Coggan suggests that a 20 minute test will suffice, but the results have to be adjusted downward by 5% to approximate a one hour test.

The Test

For 20 minutes I bathed in my own sweat as I hammered through the FTP test on my indoor trainer.

My strategy was to break the 20 minute ride into five minute blocks. I planned to start out at a slightly lower intensity than I thought could be held for the 20 minutes and then increase the intensity ever so slightly each five minutes.

Power Tap indicator

Power Tap indicator (yellow ).

What actually happened was a little different. I started out pretty well, but after the first five minutes I decided that I was at my 20 minute peak intensity already so there was no change for the second five minutes. When the 10 minute mark arrived, I was really really hurting, so I brought the intensity down a bit by changing gears and increasing the cadence. That seemed to help, so by the time 15 minutes rolled around I moved back into the higher gear. The final five minutes lasted about an hour or so it seemed.

When it was all done, my average watts for the 20 minutes was 181w ( that’s average watts, not normalized watts).


That’s a big difference from the 235w I was able to achieve several years ago. It just shows how much fitness I’ve lost in the absence of proper training. But that’s OK, because now I have my benchmark. Actually, my FTP is 181 watts minus %5 of that, because we only tested for 20 minutes, and FTP is supposed to represent one hour. That means my current FTP is 172w.

Can you tell which 20 minutes was my FTP test? (hint: between 29 and 49). The heart rate (red line) is out of sync with the power and rpm in case you noticed how flat it is from about 42 minutes on.

Proper Training

With my new FTP I can confidently train in the proper zones. For example, on recovery rides I know that my power output needs to stay below 130w. Alternatively, during anaerobic threshold workouts, the watts need to be between 157w and 182w.

The same concept applies for heart rate, so even if you don’t have a power meter, this applies to any athlete.

Until tomorrow…

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