No special documents are needed except the
consent regarding processing your personal data (download PDF
here) signed by you. This applies to all contestants, team leaders, observers and visitors. Note that if the contestant is younger than 18 years, their parent (legal guardian) must sign the consent as well.
If it's not too difficult, contact your physician and request the document that you are healthy (in any case, the team leaders should know everything about contestants' health problems and medications that they take).