Power curve query

I’ve been using Xert for almost a year and very impressed with all the features. But I have a query about the discrepancy in my power duration curve on Xert and my actual power curve (i.e. the best power I have hit for each time period, as recorded on intervals.icu):

5 secs: 658W on Xert vs. 617W on intervals (+7% difference)
1 min: 420 vs. 328 (+28%)
5 min: 268 vs. 241 (+11%)
20 min: 230 vs. 214 (+7%)
60 min: 218 vs. 207 (+5%)

I definitely feel this as workouts with intervals in the “VO2max” zone (i.e. 1-5 MMP) feel disproportionately more difficult than their difficulty score suggests for me.

Does the Xert power duration curve adapt to each individual? Or is it always the same shape? Does it take into account age/sex (I’m a 40yo female, which explains the relatively low peak power readings)? And, finally, would it be worth setting a “manual” power curve with the calculator?


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Xert predicts your best possible power curve points based on your individual fitness signature and performance under fatigue (MPA response).
See this topic: Rankings and Power Curve not reflective of my historical data - Support - Xert Community Forum (xertonline.com)

Do you complete most VO2max workouts successfully?

I actually designed myself a workout to purposefully look at what my best 1 min power would be, and it was close to 328W. Certainly I’d never manage close to what Xert predicts. At a pinch I might get within 5% of the 5 min power predicted.

Is it just that I’m bad at 1 min power? Or is my power curve out in some way?

And I really struggle with Xert’s own VO2max workouts, they feel so much more difficult than they should.

Hi Hannah,

Have you had a recent breakthrough using our new algorithm? This might help better align things for you.

If you wish to adjust things before then, you can adjust things since your last breakthrough if you had it before the update. It’s a bit involved but not too difficult:

  1. Open up the Activity Details of your last breakthrough. Scroll to the bottom. The signature is what the old algorithm found. Click the Power Duration tab to see what the activity signature estimates for 1 and 5 minute power.
  2. Click the Previous button and then click the Extract button. This is what the new algorithm found. Go back to the Power Duration tab and see what the new signature estimates for 1 and 5 minutes power.
  3. If these are more reasonable to you, click the Save button and the signature changes will be applied from that last breakthrough until today and your new signature should reflect this change.

If you run into any issues or are confused, reach out to support@xertonline.com and we’ll gladly make this change for you.

Let us know how you make out.

Using historical best mmp efforts as your targets generally doesn’t work very well since very few athletes actually do them from fresh-to-failure, well-paced at each interval. You can’t rely on this as actually what you’re capable of and what you should train with. These rarely occur during regular rides and never sufficiently to pick up how your fitness is changing with training. For example, if your last best 5 minute effort had a few moments where you eased off a bit, then the average wouldn’t be as high as compared to an effort where you didn’t ease off. Hence using best intervals is a bit flawed.

Xert’s power duration curve represents what your absolute max, fresh-to-failure, well-paced effort would be (assuming an up-to-date and accurate signature).

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That’s really helpful, thanks. I extracted my signature from my last breakthrough (which was 4 weeks ago, so a little old) and the numbers have changed to something a bit more believable…

5 secs: 667 (was 658, 617 is my best)
1 min: 402 (was 420, 328 best)
5 min: 263 (was 268, 241 best)
20 min: 229 (was 230, 214 best)
60 min: 219 (was 218, 207 best)

So it looks like it’s mainly the 1 min power that’s been revised downwards, which seems reasonable.


Max 1 minute efforts are really tough to execute without failing prematurely. Not a lot of room for error or multiple tries. You’ll need to get the gearing and power just right otherwise you end up either accumulating too much fatigue relative to the power you’re generating or getting a small pause in your power output. Either way, it’ll make reaching max 1 minute mmp near impossible (but if you get the gearing right, you’ll at least get a breakthrough :smile: all is not lost)

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