By the time many runners get into their mid- to late- 40s, age begins to take its toll.

“[Their] peak performance years are typically between 25 and 45,” said Heather Vander Weide, a physical therapist who specializes in orthopedics and sports medicine at Fairview Health Services’ Institute for Athletic Medicine in the Twin Cities. As people age, they lose lean muscle mass, flexibility and cardiovascular ability, she explained.

Vander Weide can’t turn back time but she does her best to help runners slow it down with exercises to build strength and flexibility.

“Strength training is what really protects the joint,” she said. “That’s the best defense from wearing out the joint because your muscles are your shock absorbers. … The stronger you are, the less impact on the new joint.”

Vander Weide defers to surgeons to decide whether a patient with an artificial knee or hip can return to running. But over the past decade, an increasing number are coming through her door hoping to do just that.

“Baby boomers who were active before joint replacements generally have the same drive and mind set after [surgery],” she said. “They might modify or decrease their activity but they’re asking for information about how to keep the longevity of that joint and still be as active as possible.”

Vander Weide’s advice for aging runners:

• Strength train two to three times a week, working on lower body and core.

• Get more flexible with yoga or Pilates once or twice a week.

• Build aerobic capacity with spurts of high-intensity training once or twice a week. To help find the sweet spot for that, work at 60 percent to 70 percent of maximum heart rate. Calculate maximum heart rate by subtracting your age from 220.

• Increase turnover to at least 160 to 170 steps a minute and decrease stride length, which puts less load on lower extremities and can decrease injuries.

• Add recovery days. More recovery time is needed as people age, so add rest days and incorporate low-impact activities.

“My general thought is there has to be balance,” Vander Weide said. “You have to be an athlete first and a runner second.”