Jillian Michaels poses nude for Shape, talks turning 40: 'I look better now than I ever have'

The celebrity trainer showed off all her goods for the July/August cover story and revealed why keeping her arms strong is especially important. 'I love to pick up my kids.

Jillian Michaels is aging like fine wine.

The celebrity fitness guru turned 40 in February and while the initial reaction of entering her fourth decade was shocking, she's embraced it with perfection -- both inside and out.

"I won't lie. This birthday was hard," she told Shape magazine for the July/August cover story in which she posed nude, showing off all her ripped assets.

"But when I think back on my 20s and 30s, I look better now than I ever have," the former "Biggest Loser" coach added.

Michaels' fit physique could make any woman question their day-to-day health regime, but for the mother-of-two it's really about finding what works best for the individual

"It's important for women to have overall strength, because when you feel physically powerful, it transcends into every facet of your life," she said, adding how boxing, yoga and pull-ups are all a focus in sculpting her arms.

But the primary reason she wants to have upper body strength goes beyond the physical.

"My best reason for having strong arms is because I love to pick up my kids," Michaels admitted about her two kids with partner Heidi Rhoades -- daughter Lukensia, 4, and son Phoenix, 2. The couple adopted their baby girl the same week Rhoades gave birth to their son in May 2012.

"We're swimming in babies over here," Michaels told People at the time.

Strengthening her back is also important because it gives her literal strength while making her psychologically stronger.

"Metaphorically speaking, it means I can carry a lot of responsibility on my shoulders -- and I do -- for my family, friends, and fans," she told Shape.

Aside from carrying the weight of the world on her back, Michaels finds it liberating to be in shape.

"There are so many good reasons to exercise," she said. "It doesn't matter how profound or superficial your motives are, as long as it's something that matters to you."

While overall health is what matters most to Michaels, she feels her "abs are the best part of my body," adding that planks should be credited for her rock hard core.

"Having a strong core gives you a solid foundation and helps with injury prevention, which is critical to good health," she added.

A high self-esteem is also an essential part of good health and although Michaels admitted that she carries "all my weight in my lower body," her confidence helps to subside her doubts.

"Do I want a better butt? Sure," she said. "But I'm healthy and can wear my skinny jeans, and that's good enough!"

Jillian Michael's Abs Will Make You Jealous

And oh how she wears those jeans. So well it could make a twenty something woman envious. But for Michaels, it goes way beyond skin deep.

"Yes, I'm older, but I'm also wiser, and that's a more intrinsic type of beauty," she said.