But what exactly is this challenge that's got everyone walking uphill? Let's break it down! The concept is deceptively simple: 12: This is the treadmill incline. Yep, it's quite a hill! 3: This is the ...

I’ve always been pretty skeptical of viral TikTok workouts like the 12-3-30 workout. They can be created by anyone with an account, after all, so their merits aren’t usually backed by science. But the ...