If you need a reminder of how incredibly popular the Insanity workout ... each move slowly before ramping up the speed. I started strong, but could feel myself tiring after a couple of rounds.

talk to your doctor before starting this workout. But you have to be in great shape already to tackle this high-powered workout. Do not attempt Insanity if you have heart disease or any heart ...

is the mind behind the viral "Insanity" workout. In his new book ... out with planks and making sure you've got your form down before adding in the push-ups, which can come once you've mastered ...