P90X2 - X2 Total Body.

This ain't your granddaddy's weight-training workout. X2 Total Body combines resistance and instability to ensure that your body uses the correct muscles in the given movement. Old-school isolation movements that can lead to muscular imbalance not welcome here. In this workout, you'll earn every repetition, and form is king. Instability plus resistance equals pure muscle-building efficiency with every rep.