Quick answer: FTP (Functional Threshold Power) is roughly the highest power you can hold for one hour. It's estimated with a 20-minute maximal effort multiplied by about 0.95, and every training zone — from easy recovery to sprint efforts — is set as a percentage of that number. Retest every 6-8 weeks, since FTP changes as fitness does.
FTP is the single number that structured cycling training is built around. Once you understand what it represents, the rest of the zone system falls into place quickly.
What FTP Actually Represents
Functional Threshold Power is roughly the highest average power you can sustain for about an hour before your performance starts to fall away. It's not your absolute maximum — that's far higher and only holdable for seconds — it's the sustainable ceiling that matters most for real-world riding and racing.
Estimating It Without a Lab
You don't need a physiology lab to get a useful FTP number. The common field test is a 20-minute maximal, all-out effort, with the result multiplied by roughly 0.95 to account for the fact a 20-minute effort is normally held slightly above true one-hour power. It's an estimate, not a precise lab measurement, but it's accurate enough to build meaningful training zones from.
How Zones Are Built From FTP
Training zones are set as percentage bands of your FTP, typically running from easy recovery riding at well under 55% of FTP, through steady endurance and tempo pace, up to threshold efforts right around 100%, and short maximal or sprint efforts well above 150%. Each zone targets a different physiological system, which is the whole point — riding in the right zone for a given session actually produces the adaptation the workout intends.
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Why Retesting Matters
FTP isn't fixed — it rises as fitness improves and falls during a break from structured training. Zones calculated from a months-old FTP number stop matching your current fitness, which means workouts feel either too easy or unexpectedly brutal. Retesting every 6-8 weeks during a training block keeps everything properly calibrated.
FAQ
What does FTP stand for in cycling?
Functional Threshold Power — roughly the highest average power sustainable for one hour, used as the benchmark for training zones.
How do I estimate my FTP without a lab test?
A 20-minute maximal effort, multiplied by roughly 0.95 — a useful field estimate, not a lab-grade measurement.
What are cycling training zones based on?
Percentage bands of FTP, from easy recovery under 55% up to maximal efforts well above 150%.
Do I need to retest my FTP regularly?
Yes — every 6-8 weeks during a training block, since FTP changes as fitness does.
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