Cristiano Ronaldo, Luka Modrić showing age is no boundary at Euro 2024

Aged 39 and about to play in a record-extending sixth European Championship, Cristiano Ronaldo's longevity at soccer's highest levels almost defies belief.

Luka Modrić is 38, still performing for Real Madrid and will be expected to provide the X Factor for Croatia at the Euros in Germany, which start June 14.

The best players are extending their careers for longer, despite the increased pace and intensity of the modern game.

Higher levels of fitness and stamina are being demanded of athletes, but that is being matched by ever-improving expertise in how to maximize performance.

"Sports science has had an impact on how we prepare the modern-day player in terms of diet, nutrition, lifestyle, training programs." Tony Strudwick, a sports scientist with more than three decades of experience in soccer, told The Associated Press. "We’ve moved out of the 80s and 90s with the increased level of professionalism."

Strudwick has held prominent roles at Manchester United, Arsenal and England and is currently director of medical at West Bromwich Albion.

He worked with Ronaldo at United when the Portugal forward first established himself as one of the best players in the world.

"He just set himself up for success," Strudwick said. "I said four or five years ago, knowing how professional Ronaldo was, he could play up to the age of 40. That was no problem."

With his 40th birthday in sight, Ronaldo shows no sign of being ready to quit. And with the advancement of sports science, the longevity that the likes of Ronaldo and Modrić are achieving could become the norm.

It's not so much that athletes have changed physically over the years — rather it has been a shift in mentality.

"We have seen a kind of evolution in professionalism as opposed