The Two-Dimensional FTP: Why Your "Number" Is Meaningless Without TTE

Key Takeaways:

• FTP is not static: It is a relationship between power and how long you can hold it (Time to Exhaustion or TTE).
• ROI on TTE is higher: Gaining 20 watts takes a year; doubling the duration you can hold your current power takes a month.
• Fatigue Resistance wins races: It doesn't matter what your fresh power is if you can't produce it at hour four.
• Testing requires honesty: Ramp tests over-calculate. The only way to know your TTE is to ride until failure.

When was the last time you dropped a rider because your FTP was exactly 5 watts higher than theirs? Probably never. You dropped them because 40 miles in, you could still hold your threshold power, and they couldn't.

Most cyclists treat Functional Threshold Power (FTP) like a high score in a video game—a single, static number to brag about on Zwift.

This is a physiological error.

FTP is a biological tipping point. Below it, your body clears metabolic waste efficiently. Above it, fatigue accumulates rapidly. But knowing where that point sits is only half the battle. The real question—the one the deliberate cyclist asks—is how long can you stay there?

Enter Time to Exhaustion (TTE).

The ROI of Duration Over Intensity

We all want a higher FTP. But once you exit the "noob gains" phase (usually the first 1-3 years of training), raising that ceiling becomes brutally difficult.

For a well-trained athlete, fighting for a 10-watt increase might take a full season of high-fatigue VO2 max intervals. And that’s if everything goes perfectly.

TTE offers a faster return on investment. 📉

You might currently hold your FTP for 35 minutes. With a dedicated block of extensive threshold training, you could push that to 60 or 70 minutes.

Think about the work capacity:

• Scenario A: You kill yourself to gain 10 watts. You ride 310w for 35 minutes.
• Scenario B: You keep your 300w FTP but extend your TTE. You ride 300w for 70 minutes.

Scenario B doubles your ability to perform work at threshold. Scenario A gives you a marginal speed increase for a short duration. For gravel racing, road racing, and long climbs, Scenario B wins every time.

The "Rising Tide" Fallacy

There is a pervasive myth in cycling training: "A rising tide lifts all boats." The logic suggests that if you just raise your FTP, your endurance at lower wattages automatically improves.

This is true for beginners. If you go from off-the-couch to training 10 hours a week, everything improves.

For the veteran rider, this logic falls apart. You can sharpen your anaerobic knife and boost your 20-minute power, but if you neglect the aerobic engine underneath, your TTE will shrink. You become a "glass cannon"—dangerous for 20 minutes, useless for hour three.

Muscular endurance does not happen by accident. It requires progressive overload measured in minutes, not just joules.

Fatigue Resistance: The 4th Hour Truth

Why do pros dominate amateurs even when their raw power numbers for a 5-minute climb might be similar?

Fatigue Resistance. 🧠

A top-tier rider can produce 95% of their best 20-minute power after four hours of racing. An amateur might only produce 70% of their best power after the same fatigue.

Training TTE—pushing your intervals out to 40, 50, or 60 minutes—trains your motor units to resist fatigue. It forces your body to become efficient at clearing lactate and sparing glycogen deep into a ride.

Stop Gaming the Test

If you want to know your TTE, you have to stop looking for shortcuts.

Ramp tests and 20-minute protocols often overestimate FTP because they rely heavily on anaerobic capacity. They give you a vanity number, not a performance metric.

The best predictor of performance is performance itself. ⚡️

Want to know if you can hold 300 watts for an hour? Go out and try to hold 300 watts for an hour. Ride at your suspected threshold until you simply cannot turn the pedals at that intensity anymore.

That is your TTE. It is uncomfortable. It requires mental stoicism. But it provides data you can actually use to pace a race, rather than a number that only looks good on a forum.

TL;DR

1. FTP is two-dimensional: It’s Power + Duration. Ignoring duration is ignoring half the picture.
2. TTE is easier to train: You can extend your TTE significantly in a few months, whereas raising raw FTP takes years for experienced riders.
3. Real world speed: Being able to hold high power late in a ride (Fatigue Resistance) is more valuable than a high "fresh" FTP number.
4. Test honestly: Skip the ramp test. Ride at threshold until failure to find your true limits.