This new wheely good US based fitness trend is based on the principle that your singing is a good gauge of your heart rate is at the optimal level. So If you're too out of breath to handle Spice Up My Life you need to take it a little easier. On the other hand being able to give a confident redition of The Prince of Bel Air means your not working hard enough.
Riding together as a group, singing gives students extra energy bursts and is thought to be espeically effective when much loved tunes come on. Currently the trend is US based but expect imitations in your gym any day now.
Call it a cliche but I cant wait to knock out my Bicycle Race by Queen whilst working on My Humps.