# Running Critical Power Calculator (rCP). Dr Will’s 1 & 5 method

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.

#### Simple question.

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.