Durability is how much of your performance survives after several hours of riding. Two riders with an identical fresh FTP can be very different athletes at hour four — and almost every event that matters is decided there, not in the first hour.
Why fresh numbers mislead
An FTP test measures you rested. Almost nothing you care about happens rested. The climb that decides your gran fondo comes after three hours. The moment a group ride splits comes when everyone is already tired.
Durability is the missing dimension: how much of your threshold, your efficiency and your decision-making is still there after a large amount of accumulated work. Two riders with the same number on paper can finish an event twenty minutes apart because one of them still had their number at the end.
What actually builds it
Long rides, done regularly. There is no shortcut. Time on the bike, mostly easy, is what teaches your body to keep going efficiently for hours.
Quality efforts placed late. Doing your intervals in the last hour of a long ride, rather than fresh at the start, trains the exact quality you want on race day. It is harder, and the watts will be lower. That is the point.
Fuelling. This is the one riders skip, and it is not a detail. Running low late in a ride does not just feel bad — it is a large part of why the numbers fall apart. A lot of what looks like poor durability is under-fuelling wearing a costume.
How to know whether yours is improving
Compare like with like: your power in the final hour of a long ride, across several similar rides over a block. If the same route at the same intensity leaves you stronger at the end than it did six weeks ago, durability improved — even if your fresh FTP has not moved at all.
That is the honest reason to care about this. Riders who plateau on FTP often have not plateaued at all; they have simply been measuring the wrong thing.
Your numbers, explained the moment you ask.
This is the part where fuelling stops being a footnote. Peakfy puts carbohydrate and fluid per hour on the session itself, next to the interval profile and the exact power and heart-rate targets, worked out from that ride's duration and intensity — so the long ride that builds durability is actually fuelled to be finished, not just planned.
And because it reads your whole history rather than a single test, you can ask it a question no fresh FTP number can answer: am I holding up better late than I did two months ago?
Questions riders ask
Keep reading
- How many carbs per hour cycling? A practical guide
- How to train for a gran fondo without wrecking yourself