Ronaldo practiced separately from the rest of Brazil's squad on Wednesday in the defending champion's first training session ahead of the World Cup.
Ronaldo, who had various injuries at the start of the year, ran by himself for 40 minutes while the other players underwent a series of physical drills.
Only 16 of Brazil's 23 players participated in the team's first practice session in the 5,000-seat arena built to accommodate the five-time World Cup champion at the lakeside resort city of Weggis.
The remaining seven players, including Ronaldinho, Cafu and Dida, were completing a series of physical examinations at a clinic near Lucerne.
Brazilian doctors had already stated that each player would undergo specific training depending on the results from their physical tests.
Dr. Jose Luis Runco said earlier this week that Ronaldo had been training normally for the past two weeks.
Coach Carlos Alberto Parreira said the striker will play in Brazil's tournament opener against Croatia on June 13.
"He's is in great shape and will be ready," Parreira said.
Due to injuries, Ronaldo scored only five goals in Real Madrid's first 19 matches this year and was sidelined for most of April.
The first training session open to the public was scheduled for Wednesday afternoon. More than 45,000 tickets have been sold for Brazil's training sessions in Weggis, reports the AP.