Participants set goals based on their heart rate, which can be measured by hand or using a heart rate monitor and ride simulated variations in terrain by altering resistance and cadence. If someone is new to indoor cycling and has not yet purchased a heart rate monitor then they can judge their level of exertion on an RPE (relative perceived exertion) scale. This scale has numbers which range from six (no exertion at all) to 20 (maximum exertion). Instructors guide classes by calling out the level of exertion at which participants should be. The instructor can also give a simple exertion scale from 1( no exertion at all) to 10 (maximum exertion).

Website: http://en.wikipedia.org/wiki/Spinning_%28cycling%29