Could you bench a grown man? Do you even lift? This week’s video takes us to the weight room to find out (and provide a heavy dose of old-fashioned jackassery).

Part of a stunt-work series from British free-running athletes Tim Shieff and Damien Walters, this video situates the ballsy boys in a conventional gym. They take on weight machines in completely unconventional ways, sacrifice their nether regions, and somehow manage to avoid removal from the premises.

The “ultimate motivation bench press” starts us off, then it’s all back-flipping bicep curls, and using a rowing machine with their noggins rather than behinds. Though these guys are stuntmen, and we strongly suggest you use equipment only as it is intended, we’ve also got to hand it to the video’s stars for coming up with some ingenious ways to navigate the gym. (Seriously though, it’s likely your gym staff will politely ask you to refrain from dangling from the top of a quad extension machine). These dudes even defy the logic of advanced bodyweight moves like burpees, and casually toss in some more flips. And the tri-man pushups (2:09)? Woah.

But good gravy! For your dentist’s sake — and the mere fact that it’s a dumping ground for nastiness — do not, we repeat do not, pull the cable machine’s rope with your teeth. Moral of the story: Walters and Shieff are total greatists (but actually… don’t attempt their crazy stunts).

What’s the craziest thing you’ve seen at a gym? Let us know in the comment section below or tweet the author @nicmcdermott.

Also check out Greatist’s Complete Collection of Weekly Viral Videos!