Critical Power
and W′ in 3 minutes
One all-out 3-minute erg piece reveals two numbers that drive smart training: your sustainable power threshold (CP) and your finite anaerobic battery (W′).
Quick answer
Pull a true all-out 3 minutes. CP = average watts of final 30s. W′ = (3-min avg − CP) × 180 joules. For any duration T, mean power = CP + W′/T. The 2K prediction is the watts target for T ≈ 6 minutes solved self-consistently against the Concept2 pace formula.
Accuracy & origination
W = 2.80 / pace³ converts watts to pace. The 2K prediction iteratively solves for T where predicted power and distance are self-consistent. Classification uses CP in W/kg against population norms for competitive rowers, with sex-specific thresholds. All formulas were cross-checked against published data and Concept2 official reference values.References
- Burnley, M., Doust, J.H. & Vanhatalo, A. (2006). A 3-min all-out test to determine peak oxygen uptake and the maximal steady state. Medicine & Science in Sports & Exercise, 38(11), 1995–2003.
- Vanhatalo, A., Doust, J.H. & Burnley, M. (2007). Determination of critical power using a 3-min all-out cycling test. Medicine & Science in Sports & Exercise, 39(3), 548–555.
- Vanhatalo, A., Doust, J.H. & Burnley, M. (2008). Robustness of a 3 min all-out cycling test to manipulations of power profile and cadence in humans. Experimental Physiology, 93(3), 383–390.
- Cheng, C.F., Yang, Y.S., Lin, H.M. & Lee, C.L. (2012). Determination of critical power in trained rowers using a three-minute all-out rowing test. European Journal of Applied Physiology, 112(4), 1251–1260.
- Gastin, P.B. (2001). Energy system interaction and relative contribution during maximal exercise. Sports Medicine, 31(10), 725–741.
Frequently asked questions
What is the 3MT and how does it work?
The 3-Minute All-Out Test is a single-session protocol that determines your Critical Power (CP) and anaerobic work capacity (W′). You row at absolute maximum effort for 3 minutes. During the first 30–60 seconds your power is very high as you deplete your anaerobic reserves. By the final 30 seconds, your power stabilises at a level you could theoretically sustain indefinitely — that is your CP. The total work done above CP across the 3 minutes equals your W′.
Why is CP different from my 30-min power?
CP is the asymptote of the power-duration curve — the highest power output that can be sustained without progressive fatigue. In practice, well-trained rowers can hold CP for roughly 20–40 minutes depending on conditions. Your 30-min rate-20 power is typically very close to CP (within 3–8%), but the R20 constraint caps your stroke rate, so 30-min R20 watts may sit slightly below your true CP.
What does W′ actually represent?
W′ (pronounced "W prime") is your finite anaerobic work capacity — the total amount of work in joules you can perform above CP before exhaustion. Think of it as a battery: once you go above CP, you are draining it. A typical trained rower has 5–12 kJ of W′. In a 2K race, you deplete most or all of your W′, so a larger W′ gives you more room for high-power surges in the start and sprint.
How accurate is the 2K prediction?
The CP model typically predicts 2K time within ±10–30 seconds of actual race performance. It tends to be conservative (overpredicts time) because the model assumes constant power output, whereas real races involve strategic pacing and motivational surges. The prediction is most accurate when your 3MT test was a genuine all-out effort with a proper warm-up.
How often should I repeat the 3MT?
Every 6–8 weeks, or at the start of each training block. Tracking CP over time reveals whether your aerobic base is improving, while W′ changes show anaerobic capacity shifts. A growing CP with stable W′ indicates effective steady-state training; a growing W′ with flat CP suggests you need more volume work.
Why not use 7-stroke, 60-sec, and 30-min tests too?
Those tests belong in the Energy System Analysis calculator, which profiles your three metabolic systems separately. The 3MT is a different protocol — it derives CP and W′ from a single test session, which is faster and requires less recovery. Use the 3MT for quick CP / W′ tracking between full test batteries. Use the Energy System Analysis when you want the complete dominant / limiting profile across all three fuel systems.