Now that Mike Schultz has turned 40, his pre-race routine takes twice as long as it did earlier in his career. Some days, he needs triple the time to get his muscles warmed up before hopping on his snowboard.

"I've been a professional athlete for nearly 20 years now, and I'm starting to feel it,'' he said, laughing. "My competitors are all in their early 20s. But I want to keep those young guys honest.''

While Schultz might need a little extra time to prepare, he's still one of the fastest in the world when the race is on. The St. Cloud resident will get another chance to flash his speed at the Beijing Paralympics, where he will try to defend his 2018 Paralympic gold in snowboard cross and silver in banked slalom.

The motorsports star turned snowboarder is busier than ever heading into his second Paralympic Games. His company, BioDapt, continues to supply adaptive athletes around the world with the high-performance prosthetic knee and foot he developed. Schultz relishes his time as a husband and dad, and he recently released an autobiography, "Driven to Ride.''

He's contemplated retiring from competitive sport after the Beijing Games. Then again, he might not. No matter how long those warmups take — or how many other roles he's juggling — being an athlete still energizes Schultz every day.

"I always think, 'This is going to be my last year,' " Schultz said. "I've already accomplished everything I really wanted to.

"Then I do well at an event, or I get deep into a training session, and I realize I would have an enormous hole in my life if I didn't have this. I'm a competitor through and through, and I absolutely love the process: the training, the preparation, being on the racetrack. It's 100 percent a lifestyle. It's not just something you do. That's part of what keeps me coming back."

Schultz prepped for the Paralympics by winning silver medals in both snowboard cross and banked slalom at last month's World Para Snow Sports Championships in Lillehammer, Norway. The final rounds of snowboard cross are Sunday night Twin Cities time, and banked slalom is Friday.

A native of Litchfield and graduate of Kimball Area High School, Schultz has maintained his deep Minnesota roots. He trains at Powder Ridge in Kimball, and BioDapt is based in St. Cloud. During racing season, he travels the world — accompanied by Lucky Bear, the stuffed toy given to him by daughter Lauren, 8.

His new book details the decade after the 2008 snowmobile racing accident that led to the amputation of his left leg above the knee. Schultz shifted to adaptive sports and found even greater success, winning 10 gold medals and one silver at the X Games in adaptive motocross, snocross and snow bikecross.

A lifelong tinkerer, Schultz found regular prosthetics didn't perform well for action sports athletes. He designed the Moto Knee, a high-tech prosthetic that uses a shock absorber from a mountain bike, and later created the Versa Foot. Those devices have helped hundreds of amputees get back into recreational sports, and they will be used by about a dozen snowboarders at the Paralympics.

"Last summer, we built a mini Moto Knee for a little boy named Logan, so he could ride his dirt bike," Schultz said. "Seeing him light up for the first time when he put his leg on, it was gold.

"When I had my accident, sport was the one thing that kept me looking forward in a positive direction. When you have something that you look forward to every day, it's a game-changer. It's pretty rewarding to be able to help people get back into sports and recreation."

Schultz didn't take up snowboarding until 2011, at the suggestion of X Games organizers. He's won multiple medals at the world championships and on the World Cup circuit, putting him among the favorites in the men's LL1 category (lower-limb amputation or significant impairment) in Beijing.

Writing the book gave him time to reflect on his journey. Schultz said he wanted to capture the full spectrum of emotion, from the fear and uncertainty he faced when his leg was amputated to the pride of winning a Paralympic gold medal on a knee he built in his own shop.

After the Beijing Games, Schultz will go on a book tour, then consider his future on the mountain. He's still improving his racing tactics and strategy, and he said turning 40 has motivated him to work even harder.

When he retires from racing, Schultz will continue building prosthetics to help others go faster. Until then, he will be fully focused on beating them.

"I want to push those young guys as long as I possibly can," he said. "But I know I'm going to be part of this sport, one way or another, for a long time."