Early acclaim is building up the anticipation for “Southpaw,” opening July 24 and starring Jake Gyllenhaal as a world-champion boxer whose life falls apart when tragedy strikes. Critics who have seen the film don’t pull any punches when it comes to Gyllenhaal’s performance — or his jaw-dropping physique.

To find out what it took, 24Life went a few rounds with Terry Claybon, the boxer, coach and trainer behind Gyllenhaal’s transformation. Claybon, who worked with Gyllenhaal and “Southpaw” director Antoine Fuqua, is sought by filmmakers and stars from Denzel Washington to Kevin Spacey and Matt Damon to prepare for strenuous roles.

24LIFE: How do you prepare to train an actor to portray a boxer?

TERRY CLAYBON (TC): I start off training the actor as if they were actually pursuing a boxing career. I teach them defense and how to protect themselves, same as I would with a professional fighter. I also try to educate them on the mentality and culture of the boxing world.

24LIFE: Is there a consistent philosophy or approach that you take?

TC: I make sure they understand the sweet science of the sport in terms of offense and defense. Jake was the ideal athlete to train. He walked, talked, ate, slept and lived boxing. He was dedicated not just to learning how to box, but to becoming a boxer.

I always tell my students that conditioning will give you the heart to fight, and mastering your skills will give you the confidence in the ring, which are the two things you need to be a successful fighter.

24LIFE: Do differences in the story play a role in your development of a training regimen, in addition to the physical characteristics of the individual you’re preparing to train?

TC: Absolutely, because it depends on the style of the fighter in the story, as well as the size and weight class he’s supposed to be. The training is dependent on the different types of styles: boxers, sluggers or brawlers, counterpunchers and southpaws. Boxers stick and move with the jab, brawlers are more aggressive and stalk their opponents, counterpunchers block and counter backwards and southpaws are left handed giving them a unique edge for most competitors. Muhammad Ali was a boxer, Joe Frazier was a brawler, Oscar De La Hoya was a great counterpuncher and Manny Pacquiao is one of the best southpaws out there. There’s also the shell-up style of fighting, similar to what you see Floyd Mayweather do. Jake does that in “Southpaw,” which is why his style is so incredible.

24LIFE: “Southpaw” director Antoine Fuqua asked you to train Jake, and joined him. How did you train them?

TC: I trained Jake, with Antoine alongside him, in five different styles: box, brawl, counterpunch, shell-up and southpaw. The shell-up boxing style is one I created to simulate a turtle in its shell that strikes like a cobra. When you shell up like a turtle you can’t be hit, and striking like a cobra is really quick and deadly.

24LIFE: What stands out in your mind about the mental or physical aspects of Jake and Antoine’s training?

TC: The harder I pushed Jake, the harder he worked. The more I taught, the more eager he was to learn. As for Antoine, his drive and determination brings his boxing to another level.

24LIFE: What did you observe about Jake and Antoine when they trained together? Have you worked with other directors who trained alongside their actors? How do you think it impacted the film?

TC: Since Jake and Antoine trained for the movie together, they formed a bond similar to what you see in a relationship between a boxer and their trainer. A lot of the time a trainer will show his fighter that he’s willing to go through the same things that he’s putting his student through. This helps motivate and engage the fighter. Antoine would go just as hard as Jake. They would come to the gym and Antoine would push Jake, and similarly, Jake would push Antoine. They really supported and motivated each other, and I think in the end it helped them shape the movie and Jake’s character together.

24LIFE: What was a typical day’s diet?

TC: I encouraged Jake and Antoine to do carbs early, and protein late. I kept their diet simple: you eat what is important, but everybody has a different body type and you have to keep an eye on your weight depending on your weight class. The average weight for a light heavyweight, like what Jake’s character is supposed to be, is 175 lbs.

24LIFE: What was a typical day’s workout, or some typical exercises?

TC: I had Jake work out seven days per week. They would do three hours of boxing and three hours of strength training. And they ran about eight miles a day, five times a week.

24LIFE: Did you work with them off the set and on the set?

TC: Yes, I worked with them both during pre-production and production itself. Even when Jake didn’t have fight scenes, he would work out at lunch and train on set to keep his boxing edge.

24LIFE: What important health and fitness guidelines do you recommend for kids?

TC: My advice for kids — and anyone, for that matter — is to remember that it’s important to eat a balanced and nutritious diet, while exercising daily.