AI quick summary
- Zones come from an estimated threshold and carry error — cross-check with heart rate and perceived effort.
- Track four-to-six-week trends, not single rides; fatigue and freshness shift day-to-day numbers.
- Give each ride one main goal and let the data serve it, not the other way round.
/ 01
What power zones actually are
Power zones are ranges of wattage — typically expressed as a percentage of your Functional Threshold Power (FTP) — that map to different physiological demands, from easy recovery to all-out sprint. They turn a raw wattage number into a target: 'ride here to build endurance,' 'ride here to raise your threshold.'
/ 02
Where the numbers come from (and why they wobble)
Zones are only as good as the FTP they're built on, and FTP is an estimate — usually derived from a 20-minute, ramp, or 8-minute test, each with its own biases. A meter that reads 2% high shifts every zone up. Treat the boundaries as soft, not exact.
/ 03
Use heart rate and feel to keep zones honest
Power describes output; it can't explain sleep, temperature, stress, or fueling. On a given day, a Zone 2 wattage might feel like Zone 3. Cross-check power with heart rate and perceived effort — when they disagree, trust the body and look for the cause.
/ 04
Trends beat single rides
Threshold isn't a permanent engraving. Watch changes over four to six weeks and log how you feel. A single bad day isn't a regression; a month-long trend is the only honest read on whether your zones still fit.
/ 05
One goal per ride
Give each ride one main purpose and let the numbers serve it. On an endurance ride, holding steady for the planned time matters more than chasing a higher average power. Chasing data for its own sake is how riders end up in the no-man's-land that's too hard to recover from and too easy to spur adaptation.
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