Demi Lovato's mixed martial arts workouts boost her confidence levels

Demi Lovato uses boxing, kickboxing, Muay Thai and jiu-jitsu to feel confident.

The singer, who sang about her self-assurance on 2015 hit Confident, has recently teamed her passion for sport with her love of fashion, by joining forces with Kate Hudson's athleisure brand Fabletics.

Demi, who has suffered from depression and an eating disorder in the past, has now spoken about her favorite forms of exercise, and how she finds martial arts classes to be a form of therapy for her mind.

"I feel the most confident when I'm in the gym," she told Us Weekly. "Whenever I'm training - whether it's boxing, kickboxing, Muay Thai, jiu-jitsu."

Demi's Fabletics capsule collection includes cute heart print leggings, graphic tank tops and slogan T-shirts. Some of her designs will be available later this month (May17), with more going on sale in August.

When it comes to her own athleisure style, the 24-year-old describes her look as "edgy and comfortable and chic".

It's not just fitness that keeps Demi feeling great though; she also relies on positive affirmations to boost her confidence.

"I stay confident in my own life by daily affirmations - looking in the mirror, telling myself I'm beautiful no matter what and just learning to accept my flaws for what they are and knowing that, you know, my curves are beautiful, and I am who I am," she smiled. "I hope to inspire (young women) by getting in the gym, getting healthy, feeling comfortable in their skin."

Demi's fitness range will be sold on Fabletics' website, in its 21 U.S. stores and in eight countries.