A spin bike is a stationary exercise bike designed for indoor cycling workouts. It features a heavy flywheel that provides resistance, allowing users to simulate outdoor cycling. Spin bikes often come with adjustable seats and handlebars to accommodate different body types and riding styles. They are commonly used in fitness classes, known as spin classes, where participants follow an instructor through various cycling routines. These bikes are popular for their ability to provide a high-intensity cardiovascular workout while being low-impact on the joints. Many spin bikes also include features like digital displays to track metrics such as speed, distance, and calories burned, enhancing the workout experience for users.