If you’re hoping to use spin class as a way to bulk up your backside, you may need to alter your routine or spend some time working out off the bike to increase your butt size.
4What Spinning Does
Spinning is primarily a cardiovascular exercise, causing the heart and lungs to work harder to provide oxygen and fuel for the rapidly-moving muscles of the lower body.
The main effect you’ll get from it is calorie burn — about 400 to 500 calories per session, by some estimates.
That can help you lose overall body fat, but because spin class also involves increasing the resistance of the pedals, standing on the pedals and high repetitions per minute, or RPM, the workouts will also help you build muscle.