He has five more years ahead of him at Real Madrid, but experts are positive about the longevity of Cristiano Ronaldo's football career. Dr. Mikel Aramberri, sports traumatology specialist at the Alai Sports Medicine Clinic, provides the keys to proper muscle aging.

"Cristiano Ronaldo has the correct biotype, but if injuries arise it's a different matter. Madrid has made an important commitment. I think he'll maintain a good level of performance if he doesn't get injured too much. I don't know if it will be the same as it is now, but he will still have the ability to be brilliant", Dr. Aramberri explains.

"Diet is very important. Eating foods that are rich in glycogen and carbohydrates is very important for a sportsman. Elite players are capable of self-control. They manage their strengths and weaknesses and that improves the result".

"Training should include plenty of stretching, control over the level of intensity and exercise regulation throughout the course of the season. Recovery times are also essential - down time", the doctor continues.

"Playing 50 games is not the same as 70. If Ronaldo does not pick up any injuries, he won't have problems. If he does, it will depend on what they are. Patellar tendon rupture and perhaps also quadriceps tendon rupture are the worst for a footballer's career. Another very dangerous injury is the one Xabi Alonso is suffering from: chronic adductor tendonitis", Dr. Aramberri concludes.