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The pain was real.

Some 48 hours after being put through Danica Patrick's fitness test by Danica Patrick herself — it's the basis for her upcoming book and the sort of thing that will occupy her time when retirement from racing comes — I wasn't constantly sore. But every time I stood up came a sharp reminder from my legs that Patrick had kicked my butt.

This was the workout: 100 air squats, 100 push-ups (on my knees), 100 butterfly sit-ups and 100 lunges, all timed to see how long it took to complete the set. That's the benchmark for more than 700 participants in the trial program for Patrick's "Pretty Intense" book, due out next year.

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Her fitness challenge has been an ongoing project this season while balancing her NASCAR duties. Participants sent in "before" pictures of themselves and were given access to Patrick's 12-week fitness and "clean eating" program. The results, including "after" photos, will be part of the book.

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With Patrick's driving days possibly nearing an end in the not-too-distant future, what might have seemed like an off-track hobby is being fast-tracked into something far bigger. She launched the clothing line "Warrior by Danica Patrick" on HSN after participating in the design process. And she developed the workouts and meal plans for the book.

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Ask Patrick about how much longer she will race, and her reply doesn't suggest the question is off-target.

"As long as it's fun — and it hasn't been super fun lately," she said before the season started. "But every year I start the year, I always have hope that it's going to be the year that things are going to click. I understand my career hasn't progressed.

"Maybe it's regressed? Why is that? Am I worse driver than I was a couple of years ago? Probably not," she said. "I don't think anybody gets worse. So it's really a matter of all the factors around you."

Patrick turned 35 last month. She has been racing more than half her life, building her brand along the journey and using a marketing strategy that has made her one of the most recognized female athletes in the world despite her limited on-track success. She is ranked 29th through the first seven races of the season.

Patrick drives for one of NASCAR's top teams, but the sponsorship that was so easy to come by during earlier days — remember the GoDaddy TV ads? — is now a harder sell. Before the season, Stewart-Haas Racing and primary sponsor Nature's Bakery became embroiled in a lawsuit over missed payments by the sponsor and what Patrick did or didn't deliver on behalf of the brand. It was an 11th-hour loss of about $15 million and it shed light on how hard it is to sell even the most marketable of drivers.

Now in her fifth full season in NASCAR's top series, Patrick has yet to win a race and she only has six top-10 finishes in 161 starts.

Make no mistake: She can drive. She has led laps in both the Indianapolis 500 and the Daytona 500.

But her lone victory in the IndyCar Series came in 2008 and sticks out as a glaring reminder of how her superstar status outstrips her racing resume.

It's been a popular thought for some time that Patrick eventually would make the transition to a lifestyle career, maybe becoming some version of a Rachael Ray type. This much is true: Patrick appears capable of doing pretty much anything. She can whip up a five-course gourmet meal, pair wines, paint, and dress for either black tie events or black dirt at the race track.

Is carving out a space in the lucrative health and fitness business where she ultimately wants to be?

"Sure," she said after a long pause. "If I'm going to do all this and write a cookbook and a fitness program, I'll take this as far as I can to motivate people to be successful. The program works. I know it works."

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After giving up dairy and gluten a few years ago, she really noticed the difference. She no longer would slog through a crummy afternoon and thought, "Man, today is just not my day."

"I just don't have those," she said. "The only thing that knocks me out now, sometimes, is allergies. But I don't get tired. I don't get full when I eat — and I eat all the time, too."

She is a firm believer in meal preparation, and almost always carries a cooler with healthy eating options. At Thanksgiving, she served a grain-free, dairy-free stuffing, and a cold salad of shaved brussels sprouts, toasted butternut squash and a homemade dressing.

She's gone from working out once per day to twice per day and now occasionally three times. When it comes to food, there's no such thing as a cheat day.

"Wine, and every now and again, I have too much. But that happens," she said. "But I don't ever, ever, not on purpose, cheat on food. It's a routine. When I eat like (crap), I feel like (crap). If you want to lose weight and lean out, you have to eat well."

There's been a trickledown effect on her inner circle.

Friends make elaborate breakfasts. They work out more. Boyfriend and fellow driver Ricky Stenhouse Jr. has completely changed his routines and auditioned last year for "American Ninja Warrior." Patrick's mother did the fitness challenge and has never felt better.

As for me, well, I'm not totally inactive but I wouldn't label myself a "fitness enthusiast."

I should have known I was in trouble when I arrived early for our side-by-side workout and found Patrick already warming up on the treadmill.

Or when she told me to tighten my shoelaces.

Or when she laughed out loud at my first attempt at a squat.

Truly, though, my biggest mistake was trying to keep up at the start. She was reeling off lunge after lunge in a race against the clock to beat her personal mark. It didn't take long for me to fall off her pace, and Patrick laughed later when she told me most people initially try to keep up, and instantly regret it.

I didn't finish the test. It seemed next to impossible when going head-to-head with Patrick, who completed the exercises in just over 9 minutes.

Afterward, Patrick the trainer scolded me — and offered a bit of insight into how she thinks about her own professional life.

"With racing, working out, you name it," Patrick said, "if you are not determined in your mind that you can do it, then you won't do it."

And her personal life? Well, the divorcee says she does want a family. Her April Fool's Day joke was to post a photo of herself and Stenhouse on her social media platforms suggesting they had gotten engaged.

She let it sit overnight before finally acknowledging, again on social media, it was a prank. She posted a photo of a tree swing Stenhouse had built her in the woods of their North Carolina estate.

Once so glamorous off the track, and so competitive and confrontational on it, these days Patrick is more like a love-struck, self-described hippy who preaches serenity and takes time to enjoy everything around her.

So when is that family coming? The proposal from Stenhouse?

"I got that under control," she smiled.