Robin Arzon doesn't believe in resolutions. She abides by a simple mantra: "Do epic shit." And it's defined her success.

Today, she’s the head instructor of fitness programming at Peloton, a New York Times best-selling author, and an ultramarathoner—and that’s not even the half of it. With more than 100,000 followers on Instagram, Arzon is, by definition, a fitness influencer. But that wasn't her first career path.

Before Arzon became one of today’s most in-demand fitness experts, she was a no-nonsense corporate litigator. But she experienced a harrowing situation as an undergraduate at New York University (she later went on to attend law school at Villanova University) that shifted her prerogative, perspective, and passion.

In 2002, she and 40 other men and women were held  hostage and doused with kersone by a gunman who threatened to light them on fire, according to a New York Times report.

“To put it really bluntly: When you have a gun to your head, other risky things—like following your passion and all these colloquialisms that we like to follow—really seem minimal,” she says.

After seven years as an attorney, Arzon left to pursue a career in fitness—to push the boundaries of fitness and how we train. The rest, you could say, is social media history.

That's not to say it was effortless.

“The biggest misconception," Arzon says, "you're taking a thousand leaps a day. If you're living with the right sort of risk, edge, and reward, you're going to do scary things every single day.”

For Arzon, that meant conquering feats like 100-mile ultramarathons—which she describes as “mental gymnastics”—to grappling with a Type-1 diabetes diagnosis in her 30s.

“It doesn't matter how long you're in the game, you can always take it to that next level and shake things up,” she says. “That’s where you’re going to make the most progress.”

So, if you're a gym rat hell-bent on your strength-training regimen, why not boost your cardiovascular fitness?

Here are five of Arzon’s top tips for beginner runners.