Stryd can detect CP (Critical Power) inaccuracy by checking whether the athlete’s reported RPE (Rate of Perceived Effort) aligns with what their power profile and fatigue* patterns imply for that run. The system only evaluates runs with valid RPE, sufficient duration, and usable power data. It flags CP as inaccurate if either the power-based signals or fatigue-based signals contradict the reported RPE.
This process is similar to how a running coach evaluates athlete feedback. If a coach assigns a workout that should feel “very hard,” but the athlete later reports it felt only “moderately difficult,” the coach would question whether the effort zones are calibrated correctly. The coach may then adjust those zones so future workouts better match the intended effort, sometimes resulting in faster assigned paces and/or higher power output.
[Currently, this flow is limited to users who are in an Adaptive Training Plan.]
Fatigue*:
Fatigue is Stryd’s proprietary metric that quantifies your remaining energy capacity after a run, using insights from your Power Duration Curve (PDC).
CP Updates based on RPE Post-Run Insights
The Stryd system will recognize your RPE post-run reports and compare them to your CP and suggest adjustments accordingly. This smart CP system will ensure that your Adaptive Training Plan is always tailored to your exact needs.
Here's how you can get started:
Open the Stryd mobile app
Select the Calendar icon
Select the Run Report icon on the activity you want to add RPE to
Fill out the Post-Run report and be sure to include your RPE
For more information about Post-Run Reporting and Run Tagging, please see this support article: Post-Run Reporting and Run Tagging
RPE 1–4 (Easy)
Expectation: Low fatigue and minimal time at or above CP.
Flag CP inaccurate if:
The run spends notable time near or above CP, suggesting CP is too low for an “easy” effort.
Fatigue climbs to sustained high levels or finishes very high, which is inconsistent with an easy run.
RPE 5–6 (Steady / Tempo)
Expectation: Moderate challenge with some time near CP but not extreme fatigue.
Flag CP inaccurate if:
Time above CP is very high, or average power is materially above CP, implying CP is too low.
Fatigue has either very high or very low peak/finish values, implying CP is inaccurate.
RPE 7–8 (Hard)
Expectation: Hard effort but not maximal; signals can be ambiguous.
Flag CP inaccurate if (fatigue-based only):
There is very little time above CP, implying CP is too high.
Fatigue signals are too easy (little sustained high fatigue or low peak), implying CP is too high.
RPE 9–10 (Maximal / Race)
Expectation: Strong evidence of operating at or above CP.
Flag CP inaccurate if:
There is very little time above CP, implying CP is too high.
Fatigue signals are too easy (little sustained high fatigue or low peak), implying CP is too high.
Final Decision
If any of the above inconsistencies are detected for the reported RPE, CP is flagged as inaccurate. If signals align with the RPE expectations, CP is treated as accurate for that run.
Next Steps
When the Stryd system activates the CP Accuracy Flow, the user will be prompted and given options to take action:
Update their RPE if they think they made a mistake when reporting their effort
Schedule a CP Estimate run when they feel like their CP is, in fact, wrong
Ignore the notification and keep their CP and RPE as they are.