The runs that Manny Pacquiao led through Hollywood are the stuff of legend - his feet blurring faster than his hands, for a change, as he got further and further away from the chasing pack, a never-ending battery while others wilted behind him.
To keep pace with Pacquiao - frankly, just to survive the run at a respectable distance behind him - was his way of weeding out the weak and surrounding himself by boxers worthy of his time.
If your lungs were burning and the sight of Pacquiao and his trusty dog, Pacman, was getting smaller and smaller in the distance then this probably isn't the gym for you.
Dean Byrne, an Irish welterweight, is a veteran of Pacquiao's halcyon days as a trusted sparring partner for four of his world championship fights.
Crucially, he gained respect on those long runs through Hollywood.
"I kept up with him and not many do," Byrne told Sky Sports. "I stayed side-by-side with him. He drove me. I had a burning desire to be a champion so I knew that I had to stay alongside the champion.
"He would just run off. People wouldn't catch him. When Manny goes, everybody goes."
The Irishman was used for three of Pacquiao's fights with Juan Manuel Marquez, and the Oscar De La Hoya match-up. True modern classics, and Byrne looks back now with awe and wonder that he had a first-hand view of how a boxing legend prepared.
"He was a really nice guy," Byrne said of Pacquiao. "He would invite me down for food - we'd eat at the local restaurants, he liked a little Thai place near the gym.
"He invited me to his 30th birthday party in LA!"
Pacquiao, much changed in the past 12 years, and Byrne are both now Born Again so no longer enjoy a late-night party.
"Back then, he did! We did shots together," Byrne laughs now.
The Wild Card in California, run by Hall of Fame trainer Freddie Roach, is one of the world's most iconic boxing gyms and Pacquiao is its king. The Filipino, boxing's only eight-division world champion and the only man to hold a world title in four decades, struck up a partnership with trainer Roach as an unknown but hopeful 22-year-old visitor to the USA.
Amir Khan, aged 21 and with his prodigious career suddenly questioned after he was knocked out inside one round by Breidis Prescott, also joined the Wild Card.
Tales of the sparring at Roach's gym are notorious - Pacquiao's then-promoter Bob Arum, and Roach himself, have insisted he knocked out Khan on multiple occasions.
"I didn't see it myself," Byrne says with a certain coyness.
"Khan was all over the place on many occasions and everybody at the gym knows it.
"I heard stories that he was asleep on the floor. I have heard that.
"Khan's chin is just like that. He is a great fighter, a great athlete, a super boxer, his hand speed is so fast. But his chin? He hasn't got a good chin. You can't put muscles on your chin.
"Freddie wanted him to get in, get out, get in, get out. But Khan stays in the pocket for too long to please the crowd, then he comes unstuck because of his chin."
But Craig Watson, the first man to floor Khan in an amateur bout, recently told Sky Sports: "Everyone says Khan's chin doesn't work. It's not his chin. I think it's his legs."
Either way, Byrne acknowledged: "God bless him, he gets up from the ground. He has a great heart.
"I always thought he was trying to prove to himself that he is tough. But he didn't have to prove anything. He has a silver medal from the Olympics."
Khan has chased a fight with his former sparring partner Pacquiao for years - as recently as last summer, he insisted a meeting was agreed. It never came to fruition.
What would happen, if Khan does fight the 42-year-old Pacquiao?
"Pacquiao would have knocked him out back then, yesterday, today or tomorrow. Pacquiao would knock him out forever," Byrne says.
"Khan is much faster than Pacquiao. But the power that Pacquiao poses? There is nothing in Khan's punches. When Pacquiao hits you, you know it.
"It's like a cap gun when Khan hits but it's like a machine gun when Pacquiao hits."
Byrne is retired now, aged 35. He had 18 wins from 26 fights but standing the test of time in the pressure-cooker of a Pacquiao camp, when the legend could send him home at any time, is an achievement in itself.
"I saw many people come in, get beat up, and sent home."
Byrne remembers of his time alongside Pacquiao: "It was amazing. I still want to pinch myself when I look at my pictures.
"I actually sparred with him for three world-title fights! I actually went jogging with him!
"It was surreal.
"He worked hard, non-stop. Sometimes Freddie would say 'that's enough' but he would carry on. He was absolutely relentless.
"I rose to the occasion. If I sparred with Pacquiao I raised my level to prove to him that I was game. I wanted to earn his respect and show him 'you're just a boxer, like me'."
Byrne's value was in his ability to box like Pacquiao's upcoming opponents.
"I had a similar style to Marquez - clever, smart, make Pacquiao miss, turn him around. I studied Marquez too. I can study any fighter then take on his role, like an actor!
"It was very competitive sparring. I was tactical because I was imitating Marquez. I did what he does - counter-punching."
He says of the Wild Card gym atmosphere: "Iron sharpens iron. I was in the best place to build on my potential. I needed to progress so I went into the lion's den.
"Freddie was the best in the world and I learned a great deal.
"Freddie would always make time for you, he was very dedicated. He was in the gym, from early-morning all through the day, six days per week. He's where he is today because of his hard work and dedication.
"The last time I saw him was when Anthony Joshua fought at Wembley, we walked around together and got something to eat."
Pacquiao and Roach's dream partnership broke apart in 2017, albeit briefly.
"I wasn't disappointed. I didn't know why there was a rift," Byrne shrugs. "But I could understand. Manny has always had other trainers with him, but I'm glad they came back together."
Byrne insists Pacquiao and Khan had "different mentalities" when it came to being tested inside the gym.
He says of Khan: "I used to beat him up a lot!
"When he first came over, I was sparring with him. For the first week, just like Pacquiao was, I was overwhelmed by his speed.
"He is very fast and he got the better of me in the first week of sparring. I thought 'wow'. I was just overwhelmed.
"The second week? I adjusted to his speed. The first shot I threw landed and he was all over the place. From there, I was able to time him.
"Timing beats speed.
"In a fight people won't adjust to his speed in just 12 rounds unless they have real power.
"Before he fought Paulie Malignaggi I was asked to spar with him. I studied Malignaggi. Then I did really well in sparring. But after the first spar they didn't use me again.
"I wanted to spar but I didn't know that if you do too well, you won't get the work!
"Pacquiao didn't mind the competition in the gym, he loved it."
The notoriety of Roach's Wild Card gym, and its location in Hollywood, has brought countless characters through its doors. That includes acting royalty Mickey Rourke and Mark Wahlberg.
Rourke was undefeated in eight pro fights during the 90s but some claims over his proficiency have been disputed.
"Mickey Rourke would come to the gym with his dogs," Byrne laughed.
Of Wahlberg, who has played Micky Ward on the silver screen, Byrne said: "I have pictures with him, a really nice and genuine and down-to-earth guy.
"Wahlberg kept himself in shape but I never saw him box. He would always be watching sparring. I never saw him box.
"I follow him on Instagram and he keeps in shape. I don't think he ever put the gloves on to have a spar, though."
Safe to say they are happy in the background?
"Especially in that gym, mate. It's not the gym to be playing around. You go there to fight."
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Byrne first learned how to jab at Dublin's Crumlin boxing club, the same place where Conor McGregor learned his basics before becoming a UFC superstar and boxing's highest-earning debutant against Floyd Mayweather.
"He is a great athlete," Byrne says. "To have his first professional boxing match and make so much money? Wow.
"He fought one of the best defensive fighters ever but he won a few rounds and did well.
"Floyd didn't lose many rounds through his whole career but McGregor nicked a few.
"He shows you that belief, mind-set, determination and drive can allow you to succeed."
McGregor's most recent UFC victory was met by a cryptic tweet posted by Pacquiao.
"He could hang with Pacquiao," Byrne is adamant. "Especially if he brought me into his training camp. That would be a fight I could help with.
"I told you, I can study fighters then fight like them. I watched Pacquiao for years. I can turn southpaw and fight like him.
"If that fight happens, I see myself helping Conor, as much as I love Pacquiao."