An endurance athlete named Johnny G trademarked the term Spinning, aka indoor cycling, but no matter what you call it, the workout has caught on in a huge way, and for good reason. Indoor cycling can be a high-energy workout and an efficient way to melt calories, although you control how hard you work by pushing the pace and resistance. Most gyms offer several classes to choose from through the week, though often they vary depending on the instructor. For example, at the YMCA I belong two, they have two "killer" instructors who deliver intense workouts, one who combines other aerobic drills into the 45-minute class, and another who falls somewhere in the middle. To those new to indoor cycling, it may seem odd, even pointless, to take the class in lieu of biking outside. Believe me, I'd much rather be outdoors, but oftentimes rain or high winds make the option less appealing; plus, the right cycling class can give you a really vigorous workout, and for me, as a runner, it serves as a good cross-training option. Often the class will include a mix of strength-building hill-type intervals with high resistance, and speed drills with lower resistance and a faster pace, similar to what you would experience on the road. Try it out!