I’m not a coach, a physiologist, or a lab. I’m an enthusiast who wanted a simple, repeatable way to see whether the work I’m doing is moving the needle. That’s how I landed on the 20‑minute FTP test. Do an online search for FTP test, and you’ll get tons of information on it. Some people love it, some people hate it, and some will explain why it’s the wrong tool. What I’ve learned is that a test you’ll actually do, and do the same way every time, often beats a perfect protocol you avoid. At least, that’s how I experienced it.

First, what are we measuring? Functional Threshold Power, baby! FTP is an estimate of the highest power you can sustain for roughly an hour. Coaches and all kinds of training plans use it to set training zones so “tempo” or “sweet spot” mean something more than just a feeling.

The 20-minute FTP test is just how I like it: simple. Warm up well. Do a few short primers. Then ride as hard as you can sustain for twenty minutes without detonating. Take the average power and multiply by a rule-of-thumb factor (often 0.95) to estimate FTP.

I tried a few approaches to tracking my FTP. Ramp tests are tidy and less mentally brutal for some. I need an indoor setup, no traffic, no danger, and all variables constant (super easy to do indoor, impossible to manage outside). I kept returning to the twenty-minute test because I could make it boringly similar each time: same warm‑up, fan, trainer, playlist, time of day where possible. I log the average, apply the same multiplier, and update my zones. Not elegant science, good record‑keeping.

Does the 20‑minute test “suck”? It can, in two ways. It hurts, twenty minutes on the edge always does, and it can mislead if you treat the number as gospel across contexts. Fatigue, heat, caffeine, and motivation color the result, at least for me. If I do one test after a recovery week and the next after three brutal days.. variables weren’t kept constant and that would be a problem. Change the warm‑up or switch from a trainer to rolling roads and you’ve changed the experiment. That’s why sameness is a feature, not a bug. Hold the boring parts constant and the number reflects your trend more than your circumstances.

The classic 20‑minute × 0.95 formula works on average, but individuals vary, some riders can overshoot the hour by more than 5%, others less, depending on anaerobic capacity and pacing. Ramp tests correlate too, but tend to overestimate FTP in anaerobically “punchy” riders and underestimate it in diesel types. Critical power models (built from several maximal efforts of different durations) often predict the threshold boundary more precisely, but they demand multiple hard tests and careful data fitting. The practical takeaway: pick a validated method, keep it consistent, and use it primarily to set zones and track direction over time. Consistency of protocol reduces noise more than chasing the “perfect” test does.

What I like most about repeating the same test is the feedback loop it creates. When the number nudges up, endurance rides feel easier at the same prescribed zone; when it dips, yes, it happens, I get a reality check that sleep, stress, or life are taxes you can’t out‑will. Zones shift, workouts recalibrate, and I stop guessing.

Again, not a doctor, not a scientist, and certainly not a pro athlete, but from my perspective, the key is to pick one method and defend its sameness like a ritual. That sameness turns an imperfect test into a useful tool.

Watt I Learned

I stopped chasing the “best” FTP test and picked the one I’d consistently do: twenty minutes (which in reality is longer than the 20 minutes, of course, since you have to do a warm up and warm down etc.), same setup, same routine, every few weeks. The number isn’t perfect, but the trend is honest. When I keep the protocol identical, I can see progress and when it slips, I try to take that into account as well.