FTP: what it is, how to measure it and why it changes everything

If you train on the bike with a power meter (or Zwift, or a smart trainer) and don't know your FTP, you're leaving 40% of your training value on the table.

What FTP is

FTP = Functional Threshold Power, the maximum power you can sustain for about an hour. It's your engine: everything else — zones, TSS, IF, weekly load — is calculated from it.

How to measure it (without suffering an hour)

• 20-minute test. The classic: 20 minutes at max sustainable effort, then FTP = avg watts × 0.95. Precise but brutal.
• Ramp test. 8-12 minutes of a ramp to failure. Less precise, much less traumatic.
• Estimate from real data. If you've trained with power for months, an algorithm (like Lapko's) reads your sessions and estimates FTP without a dedicated test.

Power zones (Coggan)

1. Z1 · Recovery — <55% FTP
2. Z2 · Endurance — 56-75%. 70% of your time should be here.
3. Z3 · Tempo — 76-90%. The "hard but controlled" pace.
4. Z4 · Threshold — 91-105%. Where you build FTP: 2×20', 3×12'.
5. Z5 · VO2max — 106-120%. 5×5' or 6×3'. It hurts.
6. Z6-Z7 · Anaerobic and Sprint — above 120%. Short, brutal, specific.

Watts per kilo: the number that matters uphill

Absolute FTP (300 W) says little. W/kg (FTP divided by weight) says everything: 3.5 W/kg is competent amateur, 4.5 W/kg is Cat 2, 6+ W/kg is pro. That's why weight, on the bike, is half the game.

How often to retest

Every 6-8 weeks, or when you feel a clear change in form. A wrong FTP makes every single session miss the mark.

How Lapko handles it

Lapko estimates and updates your FTP automatically from your sessions, proposes a test only when actually needed, and recalculates all zones after every update. Zero spreadsheets.