Eccentric movements – an explosive movement on the muscle contraction (eg. pushing up on a pushup or pulling up on a pull-up) and a slow release (the downward part of a pushup or pull-up) apparently results in a 40% improvement in muscle recruitment. I did my first workout last night based on this principle and loved it. The X3 Eccentric Upper workout is a great, intense 30 minute combination of pushups, pull-ups and a few shoulder, bi and tri moves thrown in. I was very well worked out and tired but not dead by the end. I think its going to work.