Strong abs power strong arms and the Arms and Abs workout targets both. It is seemingly simple and only Level II in difficulty but it doesn't take long for the load to build and the effect of it to make itself felt. Add EC for that extra challenge to the muscles and you have a workout that can bring about some pretty transformative results. Make sure you swivel on the ball of the foot on the same side as the arm doing the punching each time and breathe out explosively to activate your abs and the ab load becomes even more meaningful.
Extra Credit: 1 minute rest between sets.