Critical Power Test (bike assessment, 5 steps, ~70 min)

What this assessment is

The Critical Power Test is the seeded bike assessment that pairs with the Critical Power calculator to produce your CP (the asymptote of your power-duration curve, in watts) and your W' (anaerobic work capacity above CP, in kJ).

Domain: bike. Estimated duration: 70 minutes. Linked calculator: critical_power.

The 5-step protocol (as seeded)

Warm-up (15 min): ride 15 minutes building from Z1 to Z2 with 2 x 30 s spin-ups.
3-min all-out effort (3 min): ride 3 minutes at absolute maximum effort. Start hard and hold on.
Recovery (30 min): spin easy for 30 minutes. Full recovery is essential.
12-min all-out effort (12 min): ride 12 minutes at maximum sustainable effort. Even pacing is key.
Cool-down (10 min): spin easy.

Inputs the form asks for

3-min Average Power in W (required).
12-min Average Power in W (required).

Outputs

CP (Critical Power) in watts.
W' in kJ.

How CP and W′ feed everything else

CP anchors the Grepiac bike zones.
W' lets Grepiac project time-to-failure at any power above CP (the supra / VO2 / power tiers depend on W' being set; if W' is missing, those tiers show as "Need W' data").
Together they drive the bike split projection in step 4 of the race planning wizard.

Zone 2: measured if measured

Zone 2 is anchored on the aerobic threshold (AeT / VT1), which a CP test cannot measure — only the anaerobic side (CP) is tested here. So the zone table handles Zone 2 two ways:

With a measured AeT on file (saved from a metabolic test): one Zone 2 row, bounded by the measurement, with a note showing AeT as a % of CP and the conditioning band it implies. This matches the metabolic report exactly, because both read the same measurement.
Without a measurement: three candidate Zone 2 bands are shown (poor 60–65%, normal 66–71%, high 72–76% of CP) and the coach picks the band matching the athlete's conditioning. Where AeT sits relative to CP genuinely varies with aerobic fitness, so showing a single guess would hide that uncertainty.

Common gotchas

Insufficient recovery between efforts. The protocol specifies 30 minutes of easy spinning for a reason. Cutting it short produces a depressed 12-minute number and an inflated CP estimate.
Pacing the 3-minute too easy. The 3-minute is the ceiling of W'. If you pace it like a 5-minute effort, W' comes back low and the projections under-estimate your anaerobic capacity.
Pacing the 12-minute uneven. Even pacing produces a cleaner CP. Going out hard and fading skews the model.