If you do CrossFit, you're probably familiar with Assault bikes — the least favorite piece of equipment for many CrossFitters. That's because riding an Assault bike is tough and exhausting. So you might be wondering if you could simply replicate CAROL's REHIT workouts on such a bike, considering that they cost less than CAROL. The important thing about Assault (and similar) bikes is that their resistance goes up in a linear pattern as you increase your energy input. That's an entirely different concept than what CAROL offers. CAROL constantly adjusts the resistance based on its sensor data and your physical abilities. As a result, you won't get the same benefits (based on the same time investment) from traditional air bikes as you will from CAROL.