Hayden Panettiere has opened up about her relationship with boxer boyfriend Wladimir Klitschko for the first time, branding their union "an exciting experience."

The "Heroes" actress, 20, has been dating the 33-year-old Russian since December, but she has kept quiet about their romance.

She was rumored to have dumped the sporting star for her ex-boyfriend, Hard Rock Cafe heir Harry Morton, after they were spotted together in Los Angeles last month.

Panettiere dismissed the speculation, insisting she is "just friends" with Morton. Now the petite actress has opened up about her relationship with Klitschko while supporting him at a fight in Germany over the weekend.

She says, "I've never had an athlete as a boyfriend before, and it's an exciting experience. I think it's awesome that he's so athletic, but I'm most fascinated with his intelligence. He's unbelievably clever... .

"Even though I'm small, I can dish it out too. But I have to admit, I feel really protected with such a strong man by my side. Now, whenever someone's bugging me, I say: 'Look out, my boyfriend is a boxer!'"