From Zac Efron to Mario Lopez, see these sexy stars take their shirts off
The Avengers star flaunted his tight abs and chiseled chest in St. Barts, France. To prep for his role as a superhero, Hemsworth had to pack on 20 lbs of muscle. "It wasn't until Thor that I started lifting weights," the hammer-swinging celeb told Men's Health. "It was all pretty new to me."