(CBS) How do you become the number one fitness trainer on YouTube?
Mix equal parts sex appeal, production values and brutal at-home workouts - and you get married couple Zuzana and Frederick Light.
Their 12-minute routines regularly rack up millions of views. Their top workout has reached almost 9 million plays.
We asked Zuzana and Frederick about the rigors of staying in killer shape, managing a monster YouTube fan base, and whether 12 minutes is really enough time to get fit.