Update Ruleset.md

Author: nopara73

LongevityWorldCup.Documentation/Ruleset.md

@@ -34,6 +34,10 @@ Yes, just send us an email to `[email protected]`.
 
 ### About PhenoAge and Testing
 #### What is PhenoAge? 
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 [PhenoAge](https://pmc.ncbi.nlm.nih.gov/articles/PMC5940111/pdf/aging-10-101414.pdf) is a biological age measure based on clinical biomarkers like glucose and CRP. It reflects physiological aging, not just years lived, and helps assess health and disease risk.
 
 #### From which biomarkers can I calculate my PhenoAge?