If you want to build up a good mid section, with strong lower back muscles and abdominals that can take a punch or two, you're better off doing an exercise like the plank rather than crunches. See why in this article.
Find out how to perform the Camel Pose, which helps you in exercises such as Butterfly and Kipping Pull Ups, as well as in overhead exercises (OverHead Squat, Overhead Press, Thruster).Yoga for CrossFitters is a Prozis series.
By now, you're probably getting tired of always working your abs in the same way. Here's the second part of the abs exercises compilation, with original and effective variations to completely define your six-pack.