Listen to Justin Bieber on iHeartRadio

(Yahoo!) - Justin Bieber is having a serious growth spurt.

The 19-year-old singer, who released his latest single "Heartbreaker" — a breakup anthem thought to be inspired by his split with Selena Gomez — on October 7, shared a particularly muscly photo on Instagram Wednesday.

"Me and my trainer," Justin proudly captioned the pic.

Despite his young age, Bieber's bod has come quite a long way from the lanky string bean he was in his tween years. And he's not afraid to show it off! The pop star regularly posts topless photos of himself, giving the world a first-hand glimpse at his abvolution — as well as his ever-growing tattoo collection!

But, is it just us, or does the rippling eight (!) pack, rock-hard shoulders, and bulging biceps look a little too jacked for the pop star's small frame?

"If you combine his lean body type with the right types of supplements, like Creatine, and Weight Gainer, and other things out there in the market, not necessarily anything illegal like steroids, but a lot of things that you can just get over the counter, what you'll see are pretty quick results with the right type of weight training that look just like the photos he's been posting recently," Joey Gonzalez, celebrity trainer and COO at Barry's Bootcamp, tells omg!, estimating that The Biebs is probably hitting the weights at least four times a week.

As for his young age, Gonzalez says this type of body building isn't anything to be concerned about. "The American Counsel on Exercise says that anyone over the age of 17 is safe to lift weights and strength train. It's definitely something that as a 19-year-old you can get pretty involved with, and in a safe way."

The trainer also suspects Bieber's particularly swole frame may be a result of when the photo was snapped.

"It looks like he [took the photo] right after a session with his trainer," notes Gonzalez. "There is something called a 'muscle pump effect,' that after you lift, your muscles are actually swollen."

What do you think? Can you "belieb" the singer's physical transformation?