The Stryd system can estimate a user's Critical Power after 5 unique run activities. However, unless these unique runs contain maximal efforts for a short, medium, and long duration, the CP estimation will be incorrect. Critical Power

Maximal running efforts may not be realistic for some groups of runners just starting running. For example: after injury, illness, layoff, or those just starting running. For runners in these groups, running anything but easy aerobic efforts should be avoided for weeks (and perhaps months in some cases) - to allow aerobic fitness to safely develop.

In these situations, you will want to follow Coach Palladino's instructions carefully. See this article for further details: A method to roughly estimate FTP/CP for runners not ready to properly test