Sometimes Xert updates your Fitness Signature in a direction that doesn't match what you expected — your Threshold Power drops after a breakthrough, your HIE goes up after a steady-state ride, or other components shift in ways that seem counterintuitive. This article explains why this happens and what you can do about it.
The Short Answer
Your Fitness Signature isn't three independent values. It's a single fitted model with three parameters — Peak Power, High-Intensity Energy (HIE), and Threshold Power — that work together to explain how your performance changes over time.
When you complete an activity, Xert analyzes the full ride and finds the combination of these three parameters that best fits all the data. If the new fit produces a slightly different balance — say, a higher Peak Power but a slightly lower Threshold Power — that's the system fine-tuning your signature to best match the evidence from that ride.
So even on a breakthrough activity, individual signature components can move up or down. The total picture is what's getting more accurate.
A Common Example
You go out and produce a breakthrough effort on a hard sprint. When you look at your signature afterward:
- Peak Power went up (expected — that's what the breakthrough captured)
- Threshold Power went down slightly (unexpected — why?)
This isn't a bug. Xert's analysis concluded that a slightly lower Threshold Power combined with your new Peak Power provides a better overall explanation of your power and MPA data across the entire ride. The result is a more accurate signature, even if one component moved in the "wrong" direction.
In practice, these shifts are usually small — a few watts in either direction. They typically don't make a material difference to your day-to-day training or workout targets.
Seeing What Xert Changed
If you want to see exactly what Xert adjusted, open the activity's details page and look at the MPA chart controls:
- Click Previous to view the MPA chart using your starting signature (the values from before the activity)
- Click Current to return to the updated MPA chart using your new signature
Toggling between the two lets you see the difference in how Xert is interpreting your power data.
What You Can Do About It
You have three options when Xert updates your signature in an unexpected direction:
Option 1: Leave it and keep training
In most cases, this is the right choice. The change is usually small, the signature is now better fit to your actual data, and if any component is underestimated, you'll prove it during a future ride and Xert will adjust accordingly.
In fact, a slightly underestimated Threshold Power can make your next breakthrough easier to achieve — giving Xert a clearer signal to correct upward.
Option 2: Manually override the change
If you have a strong reason to believe the new signature is wrong, you can manually edit the values from the activity details page. See Manually Adjusting Your Fitness Signature on an Activity for the workflow.
This is the right choice when you have specific evidence the new fit is incorrect — for example, if recent ride data clearly supports the previous values.
Option 3: Flag the activity to revert the change
If you'd rather discard the activity's signature update entirely, you can flag the activity. Xert reverts your signature to its values before the activity and recalculates subsequent activities accordingly.
See Flagging an Activity for details.
When the Change Is Larger
Most signature adjustments after a breakthrough are minor — usually 2-3% or less. If you see a larger shift (10% or more in a single component), it's worth investigating before deciding what to do:
- Verify the underlying power data is valid. Power meter calibration issues, temperature drift, or sensor glitches can produce data that triggers larger signature changes.
- Compare the Previous and Current MPA charts. If the Current view shows your power data well above the MPA line for extended periods, the new signature may be underestimating you.
- Consider whether the ride was representative. A race effort with unusual drafting dynamics or unusually fresh legs can produce data that doesn't reflect your everyday capability.
If you're not sure what happened, flagging the activity is a safe default — you can always unflag later.
Want More Detail?
We covered this question in one of our Q&A videos. Watch the explanation on YouTube — the segment starts at 5:41.
Related Articles
- Breakthroughs & Near-Breakthroughs
- How to Verify Your Fitness Signature — and what to do if it seems wrong
- Flagging an Activity
- Manually Editing Your Fitness Signature on an Activity
- How to Analyze an Activity Using MPA
Need Help?
If your signature changed in a way you can't explain or you're not sure which option to take, contact support@xertonline.com with a link to the activity in question.
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