Most humans would have trouble walking in these boots, let alone scaling a Jacob's Ladder cardio machine and "running amok" with a notoriously-tough celebrity trainer like Gunnar Peterson (BTW, he's one of the trainers responsible for Khloe Kardashian's "revenge body" , among other fabulous clientele). It's your choice whether you care more about fashion than you do function, but the gym is one place where perhaps you should care a little more about what you're putting on your feet — especially if your footwear of choice keeps your calf in a compressed position. "Wearing heels in the gym creates muscular imbalances," says Jill Miller , creator of the corrective exercise format Yoga Tune Up and author of The Roll Model Method . "If her calf muscles are restrained by the position of the shoe, she can't get the full range of motion that would allow her to work her legs and body." Because she's a fitness expert, Miller also can't ignore that the position of Mariah's foot on the ladder above isn't giving her the momentum she needs to climb it. "You get your best boost from your calves and butt when you're climbing uphill or on a ladder, and she can't get the most strengthened outcome if she's on her tip toes," Miller adds.