(CNN) -- Tom Brady's Super Bowl victory continues a string of big wins for aging professional athletes -- and at 39 years old, Brady has said he has no plans to retire.
The second-oldest quarterback to win the Super Bowl after Peyton Manning, Brady signals what avid fans and sports experts are calling a growing trend of older athletes -- from mid-30s tennis icons Roger Federer, Serena Williams and sister Venus to Florida Panthers right wing Jaromír Jágr, who turns 45 next week.
"We've really started to notice it in the last five or six years," said Shawn Arent, director of the Center for Health and Human Performance at Rutgers University.
"Don't be at all surprised if ... (we see) some of these guys winning their sixth Super Bowl in their 40s," he added.
Arent said advances in the science and technology of exercise are changing not only who excels in professional sports but how star athletes are training for the big game.
Just keep swimming
On Super Bowl Sunday, former Olympic swimmer Dara Torres found herself arguing with a 9-year-old boy who predicted Brady's impending retirement. Brady, the boy said, is too old to continue playing.
"He had no idea who I was," said Torres, who last competed in the 2008 Games at age 41. That summer, she won three silver medals and set an American record.
"So now I have this bet with this kid that Brady's gonna be back next year," she added.
Torres, who won 12 medals during her 24-year Olympic career, was affectionately called "Grandma" by her teammates. But she said people learned to stop telling her that an athlete's career died at 30.
"I think I did away with that myth," she said. "Nowadays, 30 isn't that old anymore."
Torres did notice that her body had changed over the years. In her teens and 20s, her approach to training was "more is better." She trained to be physically stronger than the competition, packing on muscle in the weight room.
In her 30s and 40s, however, she realized that she could no longer pull a double workout in one day. She felt winded with the same effort.
"You can't do what the 20-year-olds are doing," Torres said.
Arent said that what is considered "old" changes from sport to sport. While athletes' bodies may change in predictable ways, he said, their performance also depends on the unique demands of the game.
Strength is one of the first things to decline with age, according to Arent. After 30, muscle mass tends to drop just a few percent per decade, but this is not something most people will notice, he said.
"For the elite athlete, where things are won and lost by fractions of a percent, then it's definitely noticeable," he said.
In one analysis of the ages when athletes reach their peak performance in different sports, researchers found two separate trends: For sprint-like events that demand bursts of power, the longer the event, the younger the age at which athletes peak. For endurance events, athletes peaked later for longer events.
By that logic, the researchers found that swimmers peaked around 20 years old while ultra-distance cyclists peaked closer to 40. And scientists have found that even cyclists older than 100 can increase their performance and oxygen consumption, despite conventional wisdom.
In sports that skew younger, athletes like Torres have gotten creative to stay on top of their games, said Arent.
"There are lessons in this for the younger athlete," he said.
"Train smarter, not just harder."
Older and wiser
Torres wasn't just losing her muscle. Her hormones were changing, and her recovery time was longer. She no longer swam through her injuries like she did in her 20s.
Maximum heart rate also falls as people age, and training may take an extra toll on muscles, joints and ligaments. Maximum oxygen consumption takes a hit. For women especially, bone density may drop after age 30. Genetics may also play a role in athletic performance.
"You can't just push it like you did when you were younger," Torres said.
Hormones that drop with age include growth hormone, a naturally occurring muscle-building compound whose synthetic version has also been implicated in Olympic doping scandals, according to the World Anti-Doping Agency.
Although the impacts of other hormones, such as estrogen, on athletic performance are less clear, exercise physiologists such as Arent say new technologies are only beginning to reveal the science of what happens when athletes train and recover.
"We've seen a massive step up in terms of our ability to monitor athletes," he said, adding that heart rate monitors, sleep trackers and biological tests are giving researchers new insight into what happens beyond the field or pool.
Using personal data, athletes like Torres may change up their routines to play past their theoretical peak. If Torres couldn't swim more powerfully, she said, she would have to swim more efficiently.
"You're gonna lose a little bit of power, but you'll make it up in the ability to do the sport in the best possible way," said Jeoff Drobot, an exercise specialist at the American Center for Biological Medicine, who worked with Torres leading up to her final Olympic tryout in 2012.
One example of improving efficiency, Arent said, was famed cyclist Lance Armstrong's low levels of blood lactate. Lactate, a byproduct of high-intensity exercise, causes a feeling of fatigue and burning in muscles; lowering these levels, said Arent, allows athletes to improve their performance -- not by increasing their maximum strength but by staying closer to their current maximum for longer periods of time.
Even then, Arent said, athletes can't turn back the clock; they can only slow it.
"As you get older ... you realize that no matter what, that window is closing," he said.
At 45 years old, Torres narrowly lost her spot in the 2012 London Olympics to competitors who were decades younger. It was then that she retired from swimming.
Of early birds and worms
Torres acknowledged that factors beyond training and willpower might be leading some athletes to stay in the game longer. Players might be having families later, making more money in some sports and realizing that it's possible to continue playing professionally past a certain age.
"People are seeing the Serena Williams, the Roger Federers, Tom Brady," she said. "Before, no one was doing it, and no one tried."
But while scientists continue to research new ways of monitoring and adjusting athletes' regimens, experts like Arent and Drobot have stressed a message of early prevention: Though exercise can benefit non-athletes at any age, elite athletes stand to uniquely benefit from an early start.
"Watch what these guys are doing" to train in their later years, said Arent.
"Now, can you apply this earlier? Imagine how much longer (your career) can be."
