Adi Erber was 4 years old when he put on his first pair of skis. Born and raised in the heart of Austria's Kitzbühel Alps, he discovered his life's passion early. Fast, flexible, and strong, his body seemed made for the sport he loved. He tested himself as a racer and ski jumper while developing an elegant skiing style that others wanted to emulate.

The rush of adrenaline Erber felt on the slopes eventually carried him across the globe to Sun Valley, Idaho, where he has been a ski coach for nearly 40 years. Skiing sometimes fills him with such joy that he startles those around him by yodeling.

"I have so much fun," he says, adding that he can't resist doing small jumps over ridges because "it feels good."

But several years ago, he started noticing that his energy was sapped. Parkinson's disease was blunting his edge. While medication alleviated some symptoms, he wasn't bouncing back. "He wasn't the smiling guy I knew," his girlfriend, Di Anna Tonello, says.

Normally, Erber is easygoing — as comfortable having a bowl of soup with a movie star after a skiing lesson as he is hanging out with the guys at the coffee shop. With a playful glint in his blue eyes and a wicked sense of humor, he earned the nickname "Naughty Adi." "He's a 19-year-old trapped in a 75-year-old body," Tonello says. "He'll always be a kid at heart."

Seeking to regain his youthful spark, Erber visited Michele Tagliati, MD, at Cedars-Sinai to explore the possibility of undergoing deep brain stimulation surgery to improve his condition. During a battery of tests before the procedure, Arnold Schwarzenegger — a close friend whom Erber has long coached — was at his side, helping him stay positive. And when he underwent the surgery in 2015, Tagliati stayed with him as he awoke. "He squeezed my hand and I squeezed his," Erber recalls. "He told me everything had gone perfectly."

Erber still coaches several days a week during ski season and goes to the gym six days a week year-round. He often looks out the window with a sense of wonder that his "office" is a snow-covered mountain. "Not bad," he says.

Read on to see how these men and women are redefining what it means to live with Parkinson’s by practicing and excelling at the sports they love.