Star couple Jennifer Aniston and Justin Theroux are obsessed with martial arts workouts.

The former "Friends" star has been enjoying yoga-style exercise Budokon for years and has now tempted Theroux to join her for similar training to improve their upper body strength and cardio.

"They've become great sparring partners. Jen's been into Budokon for years, and she and Courteney (Cox) used to do classes with well respected martial arts teacher Cameron Shayne," an insider told the entertainment website National Enquirer, reports femalefirst.co.uk.

"Jen swears by it for upper body strength and cardio and Justin's really into it now, too. It's fast becoming an obsession for them," the insider added.

The "Wanderlust" actor is said to have been initially "reluctant" to do martial arts alongside his 46-year-old wife because he was scared of harming her.

"Jen's been into martial arts for years. She's been urging Justin to try it with her for a long time, but he was reluctant because he hated the idea of hurting her. But since he tried these new routines he's become as hooked as Jen," the source added.