Ronaldo is excited about getting stuck into a full season with AC Milan.
The former Real Madrid striker said: "I cannot wait to start playing, even though we all know how important this time of pure fitness preparation is for the rest of the season.
"To participate in the Champions League from the start is an extra reason to be happy, although there will be many competitions we must prepare for throughout the whole year.
"We hope to get a good start, as this season we are all starting on a level playing field. Right now it's time to work hard, then the results will be seen on the pitch."
Ronaldo's fitness has been an issue throughout his career, so he is intrigued to benefit from the Milan Lab throughout the campaign.
"I am in good shape. It's a struggle, but then again it is for everyone in the first couple of weeks, as we need to put some petrol in the tank," added the Brazilian.