Not so long ago, Evander Holyfield was acclaimed as the consummate professional for having a home gym installed.
Joshua, whether through his pre-breakfast cardio sessions or his insistence on running on sand to emulate the balance and stability of Brazilian footballers, elevates such preoccupations to a different plane.
"He has not just set the bar in the heavyweight division," Rob Madden, his physiotherapist, argues.
"He has had a philosophical impact across all weights. In the past 10 years there has been a step up, with the boxers taking things so much more seriously, knowing that it's not just about time sparring but about what they do outside the ring. They keep focused on their success."
Madden practises on Harley Street, at the Centre for Health and Human Performance, and works with Joshua on all restorative disciplines, sometimes urging this workaholic fighter to ease up on his 13-hour days.
"AJ is unique," he explains. "I have worked with other boxers, but he has this extreme level of focus.
He will have a tough session, saying, 'I feel tired, I feel terrible', and then he immediately gets back on it, pushing himself to the limit. Our job, especially so close to the fight, is to try to put the reins back on."
To observe Joshua's custom-built musculature is to marvel at how he has rewritten the rule book for heavyweights.
The memory lingers of how James "Buster" Douglas, who shocked the sport in 1990 by beating Mike Tyson, tipped the scales at 117kg for his final bout against Andre Crowder nine years later.
Even George Foreman, the man who usurped Joe Frazier, spent the twilight of his career in comfortably-upholstered shape, looking during his swansong against Shannon Briggs as if he had had too many meals from his eponymous grill machine.
For others, intense physical discipline was far from a novel idea.
Jack Dempsey, almost a century ago, would steel himself for fights by chopping firewood, jumping ropes and swinging sledgehammers.
His concept of fortifying his neck muscles was to chew a tough gum made out of pine tar.
Joe Louis, too, ascribed his punching pedigree to a strength arising from a lifestyle of graft, which began when, for a few extra dollars, he helped his family by hauling ice up the steps of tenement buildings in 1930s Detroit.
All the recent innovations in sports science have converged happily in Joshua's favour.
While 1.98m and furnished with innate athleticism, he augments such advantages with all the extra drills he can.
He puts his remarkable endurance, for instance, down to the time that he puts in at an altitude centre, which replicates low-oxygen conditions. Plus, he follows a strict nutrition regime, involving mountainous qualities of spinach and broccoli.
His one area of flexibility, he claims, is not to follow fixed meal times and instead to "eat only when I am hungry".
Madden maintains that such self-discipline is not an imposition for Joshua. "AJ is very much a creature of habit," he says.
"He likes having the same routines, the same people." It is for this reason he and the rest of Joshua's training team are not shaking up his tune-ups unduly ahead of today's fight against Klitschko (from 9am NZT).
"One key element of peak performance is to try not to change things. It's normal, in these situations, to throw everything at him, but there is no guarantee that this would be right for him."
Joshua, Madden acknowledges, has done nothing less than shift the paradigm for what constitutes a dominant heavyweight. "From having next to no sports science in the 1970s, we now have everything possible.
There are lots of boxers who love him, respect him, idolise him, and might even hate him. But they are still in the gym, following his example."
