When professional athletes reach the highest level of competition, it's rare to see much physical improvement. They absolutely improve mentally, and that often makes a significant difference in their results, but rarely after ascending to the top do their physical skills dramatically skyrocket.
None of the PGA Tour golfers has added 40 yards to his drive since his arrival. Baseball pitchers don't go from throwing 88 mph to 98. Sprinters don't cut two seconds from their time.
And then there is the case of UFC flyweight champion Demetrious Johnson, who is an outlier in so many ways.
Johnson has been an elite fighter for years, even when he was competing as a bantamweight in 2011 and gave then-champion Dominick Cruz a very good run for his money.
Johnson, who defends his belt Saturday against Ali Bagautinov in the main event of UFC 174 at Rogers Arena in Vancouver, Canada, has made remarkable progress over the past two years and is a vastly different fighter than he was when he first joined the UFC.
"For sure, he's made a great improvement, and the public sees that over a period of time, but I can see it on a day-to-day basis," his coach, Matt Hume, said.
That's because Hume challenges him on a daily basis, putting him against bigger or better opponents. Hume, who was a fighter himself and faced the likes of Ken Shamrock, Pat Miletich and Erik Paulson, has made it a point to try to diversify Johnson's game.
And so it's why Johnson has suddenly started chasing submissions so aggressively and why he was able to knock cold the highly regarded Joseph Benavidez when they rematched for the title last year in Sacramento, Calif.
In the gym, Johnson seeks out all sorts of training partners who can teach him a technique he may not have known the day before.
"If you're not searching for people who are better than you or who have some element that you don't have, then what is your plan for improvement?" Hume said. "There are all kinds of people in the gym. I can take it up to where I'm beating him or putting him in bad positions. There are other people in the gym who can do that as well. But by the same token, there are all kinds of sparring partners and he's able to take something from each of them.
"I think what you see is a product of him being exposed to so many aspects of the game. It's not just being exposed to that, but it's also being exposed to people he doesn't even know. It's like taking Ernesto Hoost and showing him Hoost's high kick. We show him the trajectory it comes in at and everything about it. After being exposed to so much, it falls down and that's made him a better thinking fighter and able to use what he's learning in his fights."
Johnson's case is a bit different from most elite athletes, because it wasn't until late 2011, the year he defeated former bantamweight champion Miguel Torres and lost narrowly to Cruz, that he gave up his full-time job as a forklift operator.
Before that, training was a secondary concern, which makes it a bit remarkable to consider what he was able to do at that point.
Since the flyweight division was created in 2012, Johnson has gone 5-0-1 and has looked increasingly better each time out.
"This is about my two-year anniversary of being a full-time fighter under Matt Hume," Johnson said. "Before that, I was working under him just two days a week, and it wasn't enough. My second fight with Ian McCall, that's when I did it and I was strictly underneath Matt.
"Everything I did, Matt saw it and he was there every day. Doing that, I started to believe more and more in my skillset and trust in my gifts and abilities to go out and finish guys."
He's always been vastly underrated, though that is beginning to change. He's now ranked fourth pound-for-pound in the official UFC ratings, though he's hardly perceived the way other greats, such as light heavyweight champion Jon Jones, are seen.
There are few, if any, fighters in the sport who fight at as quick of a pace as Johnson does. And few have made the dramatic fight-by-fight improvement he's made.
He not only looks to traditional sources, but is also willing to learn from non-traditional sources. Many of the Seattle Seahawks defensive linemen come to train at his gym, and though none of them would ever be confused with a pro fighter, they're world-class athletes who have had success.
Johnson observes them carefully and incorporates lessons from them into his game.
"They've come out to learn arm drags and hand-fighting skills to help them get ready for next season," Johnson said. "They showed they have an open mind to be agreeable to new thoughts and concepts.
"For me, it's important to have an open mind and look for ways to learn no matter who it is from. It helps me have a good time when I'm training and it makes a difference when you're able to not get monotonous and keep diversifying your game."