Bernard Hopkins will be 40 years old when he steps into the ring for his rematch with Jermain Taylor on Saturday night (9 ET, HBO PPV) in Las Vegas. It's an age when most fighters are either hanging on in an effort to prolong their careers or well into another stage in life.
The former middleweight champion and fitness fanatic is a rarity. He remains an elite fighter after turning the big 4-0.
However, he's not alone in boxing history.
A handful of legends -- including Bob Fitzsimmons, Archie Moore and George Foreman, each of whom won championships in their 40s, as well as Sugar Ray Robinson -- remained competitive at the highest level beyond their prime.
Fitzsimmons is known best for his unlikely physique -- broad shoulders, spindly legs, "a fighting machine on stilts," according to John L. Sullivan -- and taking the heavyweight championship from James J. Corbett with his signature "solar plexus" punch in 1897 in Carson City, Nev. He weighed only 167 pounds at the time, to Corbett's 184.
Few know the Briton won the newly created light heavyweight title in 1903 -- at age 40 -- by knocking 25-year-old champion George Gardner down four times en route to a 20-round decision.
Fitzsimmons continued to fight until 1914, three years before he died at 54.
"Fitzsimmons had been a blacksmith," said boxing historian Bert Sugar. "His body was as tempered as the steel with which he worked. Obviously, he took care of himself. Fitz was always there; he wanted to fight."
The same could be said for Moore, who had 221 fights in his remarkable 28-year career.
An illustration of how long he fought: His first recorded fight, in 1935, took place only eight years after Jack Dempsey retired. Yet Moore fought Muhammad Ali.
The "Old Mongoose" spent most of his career fighting discrimination as much as his opponents, which is why he didn't receive his first title shot until 1953. He easily outpointed Joey Maxim to win the light heavyweight championship four days before his 39th birthday.
Moore went on to fight 50 times -- that's right, 50 -- after turning 40. In that span, he compiled a remarkable record of 44-4-2.
Those 50 bouts after 40 include 10 light heavyweight title defenses and two shots at the heavyweight title, losses to Rocky Marciano at 41 and Floyd Patterson at 43. He made his last light heavyweight title defense at 47.
"The only fighter who had true success at the non-heavyweight weight classes into his 40s was Archie Moore," television commentator and historian Steve Farhood said.
How'd he do it? It's a mystery.
Unlike Hopkins, who turns 41 in January and is never out of shape, Moore ballooned to well over 200 pounds between fights and then somehow managed to make the 175-pound light heavyweight limit or fight at a reasonable weight as a heavyweight.
"No one really understood it. Moore regularly fought as a heavyweight during his light heavyweight reign," Farhood said. "He'd have to take off 25 pounds or something like that, which wasn't easy at his age.
"He claimed to have some sort of aboriginal diet in which he'd chew meat but never swallow it. What it came down to in the ring, though, was he was so relaxed, so smart. He never wasted punches, never burned energy.
"And he had motivation. His dream was to win the heavyweight championship. I think that's one reason he stayed with it so long."
Robinson, the greatest fighter ever, didn't have quite the longevity Moore had, but fought fairly well in his 40s.
The experts say that lighter-weight boxers, who fight at a faster pace than their heavyweight counterparts, aren't as likely to last into their 40s. They start earlier and burn out faster.
Robinson fit that mold. He was untouchable as a welterweight and supreme as a middleweight until the mid 1950s, when he started to slow down.
Still, Robinson at 80 percent was far better than almost anyone else at 100 percent, which might explain how he remained one of the best middleweights in the world until the mid 1960s. He fought 44 times at 40-plus, compiling a record of 30-10-3 (with one no contest).
He met such capable fighters as Denny Moyer, Terry Downes, Ralph Dupas, Joey Giardello and Joey Archer (his last opponent) after 40, although he fought for no titles in his later years.
"Toward the end of his career, Ray still had good moves," said Bill Caplan, a publicist and World Boxing Hall Of Fame inductee who regularly spent time in Robinson's training camp beginning in 1956.
"The difference was timing; he just didn't have the brilliant timing he had earlier in his career. He was still wonderful punching the speed bag and doing the jump rope tricks he was known for. And he never got flabby between fights.
"He just didn't have the timing."
Of course, Foreman boasts one of the greatest comeback stories in sports history.
The jovial -- and immensely successful -- pitchman for the George Foreman Grill lost the heavyweight championship to Muhammad Ali in 1974 and retired three years afterward at 27.
Ten years later, at 37 and in the midst of a career as a minister, he gave boxing another try.
Over the next seven years, he fought himself into fighting shape and into title contention. He lost a unanimous decision to Evander Holyfield in his first second-career title shot -- at age 42. But three years later, he stunned the boxing world and then-champion Michael Moorer with an upset.
Moorer, young and quick, "won every minute of every round," in Farhood's estimation as a patient (Moorer would say desperate) Foreman waited for an opening.
It came in an unforgettable 10th round, when a straight right put Moorer down for the count and gave Foreman the title belt at an unthinkable 45 -- two decades after he lost it to Ali.
Foreman had at least one advantage over many other fighters hoping to prolong their careers: He always relied more on power than speed. And, as they say, the power is the last thing to go.
"I was able to do a lot better job in the ring when I was older because of my ability to think," said Foreman -- who paced himself the second time around -- in an e-mail interview with ESPN.com.
"I think that's a tough task when you're younger. Older people think more.
"And my style did help. My biggest asset was my power. If I'd been a pure boxer, relying on pure speed, I couldn't have done what I did in the ring."
Another apparent advantage: That 10-year layoff.
Caplan, a close friend of Foreman's since the fighter was a teenager, had an apt analogy.
"He was like a classic car with low mileage," he said, "a classic car that was put on blocks in the garage. Ten years later, when it was brought out of the garage, it still had low mileage. That's my explanation why he was able to become champ at 45.
"And he didn't dissipate. He never smoked, never drank, didn't use drugs. The only thing he did was eat too much."
Hopkins has a lot of miles on him but keeps rolling.
He probably isn't as quick as he once was, although he never relied heavily upon speed. And he can't fight at the pace he once did; he picks his spots more today, fighting in spurts to save energy yet win rounds.
Still, he has a chance on Saturday to prove he remains as good as any middleweight in the world, even though the first digit in his age is a four.
In good part, Hopkins' viability at 40 can be attributed to his work ethic: He trains year round, whether he's fighting or not, and watches his diet. Hopkins' new trainer, Naazim Richardson, who worked alongside Hopkins' longtime mentor Bouie Fisher for years, told a story that illustrates the fighter's commitment to fitness.
"He was out of the gym completely for a year [2002-03] because he was having management problems," Richardson said. "Then he came back to the gym at like 167 pounds -- 167 pounds! That's only a few pounds over the middleweight limit (160).
"He'll still be at this level when he's 42, 43, 44. Some athletes are like that; he's one of them."
Hopkins is resilient, just like Fitzsimmons, Moore, Robinson and Foreman.
Michael Rosenthal covers boxing for the San Diego Union-Tribune.