Power Preservation Profile
Critical power & W′ for CrossFit athletes
Enter two or three max-effort time trials for running or any erg. The calculator finds your critical power and W′, measures how much you fall off from your shortest test to your longest, compares it to the norm, and tells you if you’re a Powerful, Hybrid or Enduring athlete.
Your time trials
Enter each test’s length (m:ss) and your average pace (run) or average watts (ergs). Three tests of about 3, 7 and 12 minutes work best. Each test should be an all-out, evenly paced effort.
Your power preservation profile
How to use the power preservation calculator
- Pick a modality. The calculator starts on Run. Use the dropdown to switch to Row, SkiErg, BikeErg or Echo Bike.
- Enter your time trials. For each test, enter its length and your average pace (run, per km or per mile) or your average watts (ergs). You need at least two tests; three is better.
- Add another modality if you tested more than one. Each one gets its own curve on the same graph, so you can see where you hold power best.
- Read your profile. You'll see your fall-off from shortest to longest test, the norm for those same test lengths, how far you are from it, and your category: Powerful, Hybrid or Enduring.
How to run the tests
- Use about 3, 7 and 12 minutes. The model is most accurate for efforts of about 2 to 15 minutes, and spreading the tests out matters more than the exact lengths. A 3:00 and a 12:00 test alone also work well.
- Go all out, but pace evenly. Each test is a max effort for its length. A fast start and a crash will distort your numbers.
- Rest fully between tests. Take at least 30 minutes between tests on the same day, or test on separate days.
- Do a practice round. Research shows results get more reliable after one familiarization round, especially W′.
- Keep conditions the same. Same damper setting on the rower, ski and BikeErg; flat course or track for running.
- Running tests can be distances. 1,200 m, 2,400 m and 3,600 m on a track work too. Enter your time as the test length and your average pace.
What are critical power and W′?
Critical power (CP) is the highest output you can hold for a long time without your body spiraling toward exhaustion. Above it, fatigue builds fast. In running it's called critical speed (CS), which we show as a critical pace.
W′ (W prime) is a fixed amount of work you can do above critical power, like a battery. Every second you spend above CP drains it, and when it's empty you have to slow down. In running it's measured in meters and called D′ (D prime).
Your mix of the two decides your profile. A big W′ compared with your CP makes you fast in short pieces but makes you fade over longer ones. A small W′ with a high CP means you hold your output well but have less of a kick.
The math behind the calculator
We use the standard two-parameter critical power model (Monod and Scherrer), the one used in most CP research. Total work in a test equals critical power times time, plus W′:
For running, distance replaces work and speed replaces power:
The calculator fits a straight line through your tests with least-squares regression. The slope is your critical power (or speed) and the intercept is your W′ (or D′). With two tests the line goes exactly through both. With three or more, we show how closely the curve fits your tests. Rearranged, the model predicts your best average output for any length of effort:
That's the curve drawn on the graph. Other common forms of the model (power against 1/time, or the hyperbola itself) give nearly the same CP. In one study of rowers, the work–time and power–1/time methods gave 272 W and 276 W.
How fall-off and the norm are calculated
Your fall-off is how much your average output drops from your shortest test to your longest test:
For running, output is speed, so a fall-off of 10% means your longest test was 10% slower in speed than your shortest. For ergs, output is watts.
The norm is the fall-off a balanced athlete would show over the same two test lengths. Because a 3:00 vs 12:00 comparison should fall off more than 3:00 vs 7:00, the norm is recalculated for your test lengths. It uses a typical ratio of W′ to CP for each modality, measured in seconds:
R is the typical W′ ÷ CP for that modality. Then we compare you to the norm by points (your % minus the norm %) and by ratio (your fall-off ÷ the norm).
The norms we use and why
| Modality | Typical W′ ÷ CP | Norm, 3:00 → 12:00 | Based on |
|---|---|---|---|
| Run | 25 s | 9.1% (speed) | 14 trained runners averaged D′ 123 m and CS 4.94 m/s, about 25 s. Riegel's race formula (exponent 1.06–1.08) gives 20–27 s for the same test lengths. |
| Row | 75 s | 22.1% (watts) | Paul's Law (+5 s/500m each time the distance doubles) gives 67–82 s at paces of 1:40–2:00. Active adults in a rowing study measured about 98 s. |
| SkiErg | 75 s | 22.1% (watts) | Same monitor and watts formula as the rower. No published SkiErg norms yet, so we use the rowing value. |
| BikeErg | 50 s | 16.3% (watts) | Trained triathletes doing 3, 7 and 12-minute trials: CP 302 W and W′ 15.0 kJ, about 50 s. Pro cyclists run about 30–37 s, non-cyclists about 90 s. |
| Echo Bike | 50 s | 16.3% (watts) | No published air bike norms. We use the cycling value as the closest match. |
Two different sources point to the same running norm: lab-measured D′ and Riegel's race-prediction formula. Paul's Law for rowing lands in the same place when you measure in pace instead of watts (about 18–24 s). In other words, a balanced rower and a balanced runner slow their pace by about the same amount.
Why ergs fall off more than running
On the rower, SkiErg, BikeErg and Echo Bike, a fan creates the resistance, so watts rise with the cube of speed. A 3% slower pace on the rower is roughly a 9% drop in watts. That's why the erg norms are bigger than the running norm. Compare modalities by how far each one is from its norm, not by raw fall-off percentages.
Powerful, Hybrid or Enduring?
Your category comes from your fall-off divided by the norm:
| Category | Fall-off vs norm | What it means | Training focus |
|---|---|---|---|
| Powerful | More than 1.5× the norm | Big W′ compared with CP. Strong in short pieces, fades in long ones. | Raise CP: threshold intervals, tempo and aerobic volume. Pace long workouts closer to CP. |
| Hybrid | 0.67× to 1.5× the norm | Speed and endurance in balance. | Train both and retest to see which way you move. |
| Enduring | Less than 0.67× the norm | High CP with a small W′. Holds output well, limited kick. | Build W′: short, hard intervals (30 s–2 min) and VO2max work. |
The bands are a ratio, so they work the same for every modality and every set of test lengths. We set Hybrid as anything within 1.5 times the norm in either direction. W′ varies a lot between athletes (studies report a spread of 20–50% around the average), so smaller differences aren't a meaningful change in profile. The three-way split follows how coaches describe middle-distance runners: speed types, endurance types and the hybrid group in between. Research on elite 800 m runners describes the same continuum.
Most CrossFit athletes land in Powerful or Hybrid on at least one modality. That's expected: CrossFit training builds W′. A profile isn't good or bad. It tells you where your next gains are, and it can be different for running than for the rower.
How to use your profile in training
- Pacing long workouts: Hold close to your critical pace or critical power in the first half of a long piece, and spend W′ at the end.
- Intervals above CP: Each work interval spends part of W′, and rest below CP refills it. A bigger W′ lets you go harder on short intervals.
- Retesting: Retest every 6 to 8 weeks with the same test lengths. If CP rises and W′ holds, your fall-off shrinks.
- Comparing modalities: If you're Hybrid on the rower but Powerful on the run, running endurance is the bigger opportunity.
Limits of the model
- It overestimates what you can do in very short efforts (under about 2 minutes) and is less reliable past about 20 minutes.
- W′ is more sensitive to pacing and effort than CP. Practice tests improve accuracy.
- Norms are for balanced, trained athletes. They're a reference point, not a grade.
Want your training built around your profile? ZOAR Fitness coaches use critical power testing to set paces, intervals and priorities for CrossFit athletes at every level.
Train with ZOARFrequently asked questions
How do I calculate my critical power?
Do at least two all-out time trials of different lengths, ideally about 3 and 12 minutes. Plot total work against time; the slope of the line is critical power and the intercept is W′. This calculator does the math for you.
What is a good W′?
It depends on size, modality and training. Trained cyclists often have about 15–22 kJ. In one study of trained runners, D′ was about 70–180 m. What matters more is W′ relative to CP, which is what your fall-off shows.
Is a big fall-off bad?
No. It means more of your performance in short efforts comes from W′. That helps in sprints and short workouts. It shows you'd gain the most from raising CP.
Can I compare my run and my row?
Yes, by comparing how far each one is from its norm. Raw fall-off percentages aren't directly comparable, because watts on a fan-based erg drop about three times faster than pace.
How often should I test?
Every 6 to 8 weeks, with the same test lengths and setup, so changes reflect your fitness and not the protocol.
Sources
- Jones AM, Vanhatalo A. The "critical power" concept: applications to sports performance with a focus on intermittent high-intensity exercise. Sports Medicine, 2017. Link
- Jones AM. The "critical power" concept and high-intensity exercise performance. Gatorade Sports Science Exchange. Link
- Karsten B, et al. Reliability of the parameters of the power-duration relationship using maximal effort time-trials under laboratory conditions. PLoS One, 2017. Link
- Galbraith A, et al. Comparison of critical speed and D′ derived from 2 or 3 maximal tests. International Journal of Sports Physiology and Performance. Link
- Vinetti G, et al. Critical power and W′ of professional cyclists (Giro d'Italia data), 2022. Link
- Cheng CF, et al. Determination of critical power in trained rowers using a three-minute all-out rowing test. European Journal of Applied Physiology, 2012. Link
- Evaluating high-intensity interval-training validity using critical power in rowing. Link
- Paul's Law: +5 seconds per 500 m for every doubling of distance. Link
- Riegel PS. Athletic records and human endurance. American Scientist, 1981.
- Sandford GN, et al. Anaerobic speed reserve: a key component of elite male 800-m running. International Journal of Sports Physiology and Performance, 2019. Link
- Williams S. Critical power: a useful concept for functional fitness athletes? Link
- Auciello E. Critical power as a measure of fitness. The Performance Menu. Link
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