When stryd uses it’s “auto-CP” it takes a 90-day window and applies a decay for 30-day segments. It appears like their calculation prioritises time in their calculations.
The problem with using time is you only get a snapshot of a larger effort unless you specifically did a best effort for that time.
An example is using their 3min and 9min CP calculation. When I looked at my data. My peak 3min came from a 2km (6min) effort, and my 9min came from a 5km (15min) effort. In this instance, my CP is underreported because if I was going to do a 3min or 9min I would run much faster/harder.
Use distance instead. 1km and 5km.
Do you care about your best 3min power or your best 1km time? Same question for 9min Vs 5km?
Scientists have shown that time is a harder reference to perceive than distance. As such, distance-based time trials elicit greater outputs from athletes.
3min is simply a number that represents your anaerobic peak. It’s better to use a 1km, which for most, will be 3 – 5min.