Oleksandr Usyk's strength and conditioning coach has said the 38-year-old is showing no signs of slowing down and is getting stronger ahead of his rematch against Daniel Dubois.
There is a significant age gap between Usyk (23-0, 14 KOs) and Dubois, 27, who go head-to-head for a second time Saturday in London for the undisputed heavyweight title.
Usyk outclassed Dubois (22-2, 21 KOs) in Poland two years ago, winning by knockout in Round 9 after composing himself following a low blow in Round 5.
Dubois has always maintained the punch was legal, but it overshadowed what was a largely dominant performance from Usyk, who was ahead on all three judges' scorecards at the time of the stoppage.
Dubois has been on a three-fight knockout streak since then, with wins over Jarrell Miller, Filip Hrgovic and Anthony Joshua.
While he may be the older opponent, Usyk's trainer, Jakub Chycki, has said the Ukrainian is not showing signs of aging as he prepares for his 24th professional bout.
"He is able to perform the same training loads, the same type of training, we see he's a little bit stronger, generates more power," Chycki told ESPN.
"The aerobic capacity is on the same level. So in my opinion we don't see the symptoms of aging now. So it's a good prognostic for the next fight."
Usyk is closely monitored throughout camp and various data collected while he spars and trains.
Chycki said all of the responses have been positive.
"For me the most important thing is not [to be] worse at this age," he said.
"We know his history. In sports science, the most important thing is monitoring response on the training loads.
"Different parts of stressors: Physiological stressors, psychological stressors, mind traumatic brain injuries so, reaction on the sparring sessions.
"Now we see the response, no change."
However, Dubois is also at the top of his game physically and is expected to try and impose himself on Usyk early in the fight, as he did in September when he dominated Joshua.
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Dubois' promoter, Frank Warren, believes Usyk will meet the Brit in the middle of the ring and expects a similar start to the Joshua fight.
"Do what he did against Joshua. Start fast, use his jab, he's got a superb jab, use all his physical attributes," Warren told media when asked how Dubois could beat Usyk.
"He won't have to go looking for Usyk. You look at Usyk against Joshua, you look at Usyk against Daniel the first fight. You look against Tyson [Fury]; he comes out and stands with you, which is great. That's what I want."