I consider myself a pretty decent cyclist: during my commutes I’m usually the one who overtakes others, or I can ride a hundred kilometers at a more leisurely pace. That’s all anecdotal, however, and it only occurred to me recently that there are ways to actually measure how good one is at cycling, without taking part in competitions: enter power and watts.

Those more serious about cycling keep an eye on their wattage (more precisely, power) and very likely have high-end bike computers that display the wattage in real time. In short, the watts tell the power the cyclist can generate, and the more power the faster they can go, basically.

So what if you’re a more casual cyclist like me and don’t have nor want to invest in a cycling computer? In my case I recently got myself a gym membership after some thirteen years away. (As a side note, it was weird to notice that all the weights had been recalibrated during the last decade! For example, a 10 kg dumbbell definitely wasn’t that heavy the last time I tried!) At my gym are several Matrix exercise bikes, which have a fitness-test program. The program asks you to maintain a cadence (pedaling rate) of 60-80 RPM (revolutions per minute), and then it ramps up the level every two minutes, making it harder and harder to pedal. Once you can’t sustain the 60-80 RPM cadence, the test ends.

In my case I found that a leisurely pace is, for me, about 58 RPM, so already maintaining the required cadence took some conscious effort, even when the resistance was initially negligible. I got exhausted at around 14 minutes and 30 seconds, at which point the device displayed the final results: estimated VO₂max (maximum oxygen intake) of 46,7 ml/kg/min and then just “245 Watts”.

The VO₂max value is good or very good for a male in my age group according to different normative tables, but I don’t remember entering my weight into the device and I doubt it measured it either, so I’m taking that with a grain of salt. However, the watts was what I was interested in in the first place, and that the device should be able to measure precisely. But what kind of a figure is that? I tried to find the manual of the bike and even sent a query to Matrix to find out, but to no avail.

My own research and asking around suggests that the value is probably the peak power output, estimating the maximum aerobic power (MAP). The MAP clearly isn’t that interesting a figure, since you cannot maintain that kind of a power for any prolonged period at all, so what we’re interested in instead is the functional threshold power (FTP), which reflects a rider’s sustainable power output level. According to the online sources I found, a decent estimate of FTP is 0.75×MAP = 183.75 W. (Individual variation exists, though, so in practice the FTP is usually somewhere between 0.7×MAP and 0.8×MAP.)

Fine, but how does that value compare, then? Alone, it doesn’t really tell much so it needs to be scaled for the rider’s weight, and in my case this power-to-weight ratio rounds to 2,0 W/kg. Most tables I found are for professional athletes, which I’m not, but 2.0 W/kg is still good for an amateur. A club cyclist would have the ratio at around 3.0 to 4.0, and the very best of the best cyclists in the world have the ratio of some 7.0, which is just insane, translating to them riding steep uphills roughly as fast as I commute on flat ground.

To double check the results by the Matrix bike I did the test again a week later and got the same results, so at least it’s internally consistent. Next, I tried this online calculator, plugged in the numbers from one of my regular commutes, and arrived at 2.1 W/kg, which is close enough to 2.0. (I use Strava to record my commutes, but only because it has an API. I find the free version of Sports Tracker a much better app and used that one for years, but they don’t have an API, which I need, so what can you do.)

So, what did we learn? The functional threshold power is a good way to measure the relative “goodness” of a rider, but calculating it without a proper cycling computer might not be entirely trivial. Also, for casual riders like me, the figure is basically useless anyway, unless I start to train regularly and in a determined way, at which point I’m not exactly a casual rider anymore. There are also several different methods of estimating the FTP, such as the ramp test that I described, but also an 8-minute and 20-minute test. Anyway, at least I found all this interesting, and in the end that’s all that matters for a blog post!