How Quickly Do You Lose Physical Fitness?

After Kelly Gillen completed the JFK 50 Mile in November 2016, she intentionally prepared to settle into a two-month break, give or take. The long-distance run, nearly twice the length of a marathon, had taken a lot out of the avid runner, who assumed she’d be raring to go again come January. But the 38-year-old scientist, who lives in Brooklyn with her husband and dog, quickly realized there was a problem when she hit the pavement again after her hiatus.

Gillen’s first run in early 2017 was unexpectedly painful, leading her to seek medical attention. Multiple visits with an orthopedist, along with two MRIs (magnetic resonance imaging scans), revealed that Gillen’s knee discomfort was due to a loss of cartilage under her kneecaps. She had to spend months in physical therapy and doing strength-training exercises before she was able to run again.

The unintentional time off resulted in a loss of fitness. For years, she used running as a way to clear her head and zone out. But post-injury, things were different. “I had to be very aware with each step,” Gillen says. “I basically had to relearn how to run,” she says.

She couldn’t go as fast or as far, and she couldn’t zone out because she was so focused on maintaining her form and not overdoing it. Although Gillen was thrilled to be able to run again, it was months before the movement felt as natural and effortless as it had before.