Nine-year-old Lauren Harvey has been playing tennis since she was 4. She recently started playing in her first USTA junior tournaments, and she religiously checks her USTA ranking online each week. This weekend, she’s playing in a tournament at her home club, The Greens in Oklahoma City. But it’s not just any tournament, and tennis is more than just a childhood obsession for her. The tournament is to benefit the Cystic Fibrosis Foundation, and since Lauren has cystic fibrosis, playing tennis is helping to keep her healthy.

A genetic disease that changes the way secretions happen in the body, CF causes mucus to thicken and clog wherever it is in the body. For the lungs, that can mean clogged airways, which can lead to breathing difficulties and infection. Aerobic activity helps clear the lungs, so it’s absolutely necessary that those with cystic fibrosis lead active lifestyles.

“What happens is gradually over time you lose functioning in the lungs,” says Dr. Mark Harvey, M.D., father to Lauren and her brother, Will, 13, who also has CF and also plays tennis, though mostly as a way to stay in condition for his favorite sport, auto racing. “The goal is to make that happen as slowly as possible.”

What’s more, Harvey told me as he drove his daughter home, aerobic activity helps condition the entire body, which is extremely important when you have a chronic disease. “People who are better conditioned live longer lives with better quality,” he says. “If they get an infection, the better condition they’re in, the better they’ll be able to deal with it.”

In 1955, when the CF Foundation was founded, children with the disease weren’t expected to live through elementary school. But after strides in treatments and therapies, the median survival age today is 37. Dr. Harvey says there have been some major research developments recently, and he’s most excited about trials on therapies to correct the functioning of the defective protein created by the abnormal gene that causes CF. “There’s a good chance that those people who are alive right now with CF may have the chance to have normal life spans,” Harvey says.

The junior tournament this weekend, in its first year, is the latest of many CF fundraising activities for the Harvey family. They do a golf tournament that raised $200,000 this year, the Great Strides nationwide walk, galas to raise funds and an adult tennis tournament at The Greens in February that raised $15,000 this year.

Another reason Harvey and his wife, Diane, encourage their kids to be active? “When you’re dealing with chronic illness, staying active and engaged and thinking about the future is important,” he says. “Like with tennis, positive self-talk, visualizing success and goal making, those are the same things that are important.”

Let’s hope Lauren takes that positive attitude and determination to the court this weekend.