How Athletes Can Stay ‘Fast After 50’

As we get older, most of us get slower. But aging athletes may be able to stave off those changes more successfully than most people realize.

That’s the conclusion that Joe Friel, a celebrated triathlete, coach and author, reaches in his new book, “Fast After 50.” As he approached his 70th birthday, Mr. Friel began researching how aging affects athletic performance.

Among his primary findings: Many older adults are capable of pursuing high-intensity workouts well into later life. Put simply, “to be fast, one needs to train fast,” Mr. Friel says.

“If we do this, our aerobic capacities decline at a slower rate,” he says. In fact, “people will live longer with high-intensity training than if they adopted a long-slow-distance approach to exercise, which is what most of us do.”

We exchanged emails with Mr. Friel at his home in Boulder, Colo. Here are edited excerpts from that discussion.

It’s the hormones

WSJ: At what age do we start to slow down, and what happens, in a nutshell?

MR. FRIEL: Most endurance athletes will begin to notice a change in performance by their late 30s. The change is mostly the result of decreasing hormone production.

When we’re young we release lots of anabolic—tissue-building—hormones: testosterone, growth hormone, insulin-like growth factor, etc. These have a lot to do with recovery and damage control. As we age, the body gradually produces less and less. That means even slower healing of injuries and slower recovery as we move into our 40s, 50s and later.

WSJ: How would you sum up your research? How do we keep from slowing down?

MR. FRIEL: The best way to maintain health and performance for the dedicated but aging athlete is by doing high-intensity interval training, doing strength training with heavy loads, including adequate protein in the diet, and getting lots of sleep.