Ex-UCLA gymnast Katelyn Ohashi -- one of the stars of ESPN's Body Issue -- says she was nervous as hell to strip down for cameras, telling TMZ Sports, "It took a lot of courage!!!"
Ohashi had a meteoric rise to fame this past year ... after an awesome floor routine at UCLA in January (59 MILLION people watched it!!!) -- she became a household name.
So much so, ESPN's producers asked her to appear in the buff in their magazine ... and even though she absolutely killed it -- she says it was terrifying!