Taking on the challenge of playing Muhammad Ali was not a role Will Smith was going to take lightly.  

His boxing trainer has revealed how the actor, then 32 years old, underwent an intense training session in order to transform himself into the greatest athlete of the last century. 

Hollywood-based mentor and life coach Darrell Foster told NME how he got the father-of-two in shape using the tried-and-tested methods of endurance training combined with boxing-based cardio. 

The trainer, who also counts Antonio Banderas, Woody Harrelson and Eddie Murphy as his clients, is known for his eccentricity. 

He explained how he pushed Smith to the very limit to achieve the best results.   

The ex-professional boxer told NME: “I took Will up to 10,000 feet in Aspen, Colorado so he could understand what it felt like to experience oxygen deprivation in order to correlate it to how Ali felt in the 14th round with Joe Frazier and how it feels to actually not be able to breathe and you’ve still gotta [sic] keep fighting,"

"I made Will run and throw punches. He fell to his knees and I made him write Ali’s name in the snow. And he said: ‘Now I get it’.”

Foster has also revealed how Ali gave Smith pointers on how to speak like the former heavyweight world champion in the 2001 biographical sports drama film.  

“He was on set maybe three or four times, mainly to harass Will," said Foster. "He was mainly there to teach Will to improve his dialogue. He’d often go, ‘No man that don’t sound like me.’ He’d say, ‘It’s Joe Fraaazier, Fraaazier’.”

Speaking to ABC News in 2001, Smith spoke openly of his admiration for the man who he described as 'a champion in the fight against injustice.'

“For nearly two years I worked to transform myself into the man who changed his name from Cassius Clay to Muhammad Ali and shook up the world,” said Smith. “And that’s really what makes my job so beautiful as an actor — for four, five months at a time I get to wear peoples’ lives.

"So I got to wear Muhammad Ali’s greatness. I got to study and feel and embody the soul of the man, from the foundations of Islam and the strength of his Muslim faith in his life, to the beautiful wake that he always leaves in his magnificent path.”

“What I learned about the word legacy “is that it extends far beyond our professional accomplishments; it extends far beyond accolades.

"Muhammad Ali is a champion for civil rights. He is a champion in the fight against injustice. He is a champion for utilizing whatever tools he has to make the world a better place.”

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