All indoor bikes are not created equal. You can spend an hour-plus churning away on a spin bike . But don’t try that on the Airdyne. That’s because the Airdyne is a master of resistance . The harder you work, the more challenging it gets. There’s just no way to half-ass a session on it. Hence, its nickname: the Misery Machine. The Total-Body Workout That’ll Help You Get Killer Abs Unlike a spin bike, which derives its resistance from a flywheel the rider sets manually, the Airdyne employs a giant fan; the more power you generate through pedal strokes and push-pulling the handles, the more resistance the bike generates. That’s one reason the Airdyne has a cult following among pro athletes, trainers, and CrossFitters. However, a bike with a resistance dial is still better for longer, steady rides. Another reason it’s so popular: “It requires almost no technique, so you can work really hard from the get-go,” says Pat Davidson, a New York City–based strength and conditioning coach.