Zac Efron 's latest shirtless  moment isn't one for the faint of heart. In the series premiere of NBC's Running Wild With Bear Grylls, airing July 28, Zac whips off his shirt , flexes his flawless muscles, and rappels down the side of a cliff with adrenaline junkie Bear. "I can't believe how high this is," Zac says in a preview of his daring stunt. If that doesn't make you nervous, prepare yourself for the clip in which Zac jumps out of a helicopter with the confidence of an action hero.
The scary moments don't stop there — in a third clip from the episode, Bear talks Zac through crossing between two cliffs on a rope. Yes, a rope! As it turns out, Zac was up for the challenges. "We reached out to him, and he kindly said he was a fan of the show and that he was in 120 percent," Bear told People. "He asked for the biggest, baddest adventure, and it was an honor to oblige."
Showing off his athletic prowess is nothing new for the heartthrob. When he wasn't busy kissing Michelle Rodriguez  or going on a shirtless horseback ride  as he did during his vacation in Italy earlier this month, Zac got seriously active  on a boat and the pavement. If you need to calm down after watching all the excitement, feast your eyes on Zac's hottest shirtless pictures !