Spinning

Spinning is a popular work-out available in most fitness facilities. Usually there are 10-20 stationary cycles set up in a room and an instructor leads a group in the spinning workout. The spinning workout is meant to simulate riding a particular outdoor course. Some spinning rooms have video screens so the participant can 'see' their riding course, while other spinning facilities have special lighting designed to increase motivation. While most facilities say that spinning is for everyone, the workouts can be very intense. So if you decide to 'spin', have plenty of fluids available and listen to your body.

Reference: http://www.acefitness.org/fitfacts/fitfacts_display.cfm?ItemID=85