Battle of the blonde and brunette beefcakes!

Chris Hemsworth, star of The Avengers and Snow White and the Huntsman, showed off his six-pack abs and bulging biceps at the Park Hyatt Hotel in Sydney, Australia June 18. The actor and father to India, 5 weeks, added 20 pounds of muscle to his 6-foot-3 frame to play the titular role in 2011's Thor.

PHOTOS: Hollywood's hottest, shirtless hunks

To become the hammer-wielding superhero, Hemsworth, 28, worked with trainer Michael Knight, who told Men's Fitness he devised "a bodybuilder-type protocol focused on high-weight, low-rep moves designed . . . [and] total-body circuits designed to shift his excess fat while maintaining muscle."

VIDEO: See Chris Hemsworth in action in The Avengers

Hemsworth admitted that although his workouts with Knight were "exhausting," they were well worth it. "I prefer to be training than not. It gives me more energy and I just generally feel better about myself," he told the magazine. "I feel like I've earned that beer at the end of the week."

PHOTOS: Joe Manganiello's hottest shirtless shots

Hemsworth wasn't the only buff star to show off his sexy, shirtless body this weekend: Joe Manganiello, 35, stripped down in Miami Beach June 17. The actor, who plays an exotic dancer named Big Dick Richie in Magic Mike (in theaters June 29), is no stranger to taking off his clothes, thanks to his role as a werewolf on HBO's True Blood. To look good for nude scenes, Manganiello exercises twice a day, six days a week.

VIDEO: Joe Manganiello tells Us how he stays in shape

"My trainer, Ron Matthews, is the best in the business. So I pay him money to kick my ass!" the actor told Us Weekly in 2011. "It's a brutal 60 minutes three times a week, and then the other nine workouts are on my own."

Tell Us: Which buff actor has the hotter beach body?

This article originally appeared on Chris Hemsworth vs. Joe Manganiello: Whose Shirtless Beach Body Is Hotter?