WHAT IS FTP?

FTP (functional threshold power) is the highest average power, in watts, that you can sustain in a quasi-steady state for roughly an hour. Push above it and fatigue starts stacking up quickly; sit below it and you can keep going for a long time. That tipping point is why FTP is the anchor for almost every structured cycling plan.

Physiologically it sits close to your lactate threshold — the intensity at which lactate production and clearance stop balancing out. FTP is the practical, bike-shaped version of that lab measure: you can find it with a power meter and a hard twenty minutes, no blood samples required.

• It sets your zones. Every training zone is a percentage of FTP, so one test defines the targets for recovery spins, endurance rides, sweet spot, threshold and VO2 max work.
• It makes progress visible. Feeling fitter is unreliable. Twenty watts more at threshold is not.
• It is comparable. Divide FTP by your weight and you get watts per kilo, the number that predicts how you will climb.
• It makes indoor rides purposeful. Without FTP a turbo session is just sweating. With it, every interval has a target band you either hit or miss.

The terminology gets muddled, so here is the short version of who means what.

For anyone training at home, the differences are academic. Pick FTP, test it the same way every time, and the trend is what matters.

Once you know your FTP, zones fall out of it as simple percentages. This is the Coggan-style seven-zone model used by most apps and coaches:

A worked example

A rider with an FTP of 240W has an endurance band of roughly 134-180W, sweet spot around 204-228W, threshold repeats at 218-252W and VO2 max efforts at 254-288W. Change the FTP and every one of those numbers moves with it — which is exactly why a stale FTP quietly ruins a training block.

Every four to eight weeks is plenty. Test more often and you spend your good days testing rather than training; test less often and your zones drift out of date. If a workout that used to be hard now feels comfortable, or you fail sessions you used to complete, that is your cue.

FTP also moves with your form, not just your fitness. A number set at the end of a big block will feel brutal after two weeks off the bike, so retest after any long break rather than soldiering on with old targets.