The neon yellow walls at Slash Fitness don't surround treadmills, bikes, or simple dumbbells. Instead, they shelter a spacious interior equipped with power blocks, kettlebells, medicine balls, and TRX trainers—primal workout gear that encourages exercisers to challenge their limits while seasoned instructors guide them through semi-private crucibles. Inspired by Combine360, this rigorous approach to fitness landed Slash Fitness an endorsement from workout-wear giant Under Armour. Each 45-minute class tests that company’s famed moisture-wicking prowess, summoning sweat while strengthening muscles, bolstering cardiovascular endurance, and burning fat. The gym’s instructors also change their exercises on a daily basis, preventing plateaus, boredom, and crippling bouts of workout déjà vu.