Nick Foles is less agile than Carson Wentz, and his arm is not as strong _ two reasons football pundits cite for why the beloved backup quarterback will not be on the Eagles' roster next season.
A third difference between the two does not take an expert to appreciate. At age 30, Foles is four years older.
True, Tom Brady is more than a decade older than Foles, and he just scored his sixth Super Bowl win with the New England Patriots. Then there is tennis great Martina Navratilova, who won the 2006 U.S. Open mixed doubles title a few weeks before turning 50. And what of Ed Whitlock, who, at age 73, ran a marathon in 2:54:49?
Notwithstanding those elite performances, experts in human physiology say that certain physical traits start to slide even before age 30.
An athlete can compensate for some of the decline with training, expertise, and, in a team sport, support from teammates, said Angela D. Smith, past president of the American College of Sports Medicine and an honorary professor at Thomas Jefferson University. Think of the veteran baseball slugger who is good at guessing what type of pitch is coming. Or the aging quarterback who gets an extra split-second to throw the ball on every play because he is protected by skilled offensive linemen.
But ultimately, the race against time is one we all are going to lose. The body becomes less adept at converting oxygen into energy. It needs more time to recover from injury. Muscle mass is harder to maintain. Eventually the brain _ the quarterback of our biological functions _ does not crackle with the same youthful quickness.
"Something happens to people in their 30s," said Michael Joyner, a physiologist and anesthesiologist at the Mayo Clinic. "If they train really hard, it will be their later 30s."
Determining exactly when each physical trait starts to go is tricky.
The type of study needed to nail down the answers would be long and expensive. Scientists would have to follow a group of athletes for decades, comparing individuals' performances later in life with those from when they were younger. Training and diet would have to be kept constant.
Instead, some researchers have studied age-related physical decline with a snapshot approach, measuring a specific trait across a large group of younger and older people at one moment in time. Others have analyzed record times in running or swimming races for different age groups, reasoning that those are a good indicator of the best possible performance at each age.
While each approach has its limitations, researchers have a good idea of how age affects these key aspects of athletic performance:
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