The Diagonal Chop Upgrade
The cable chop exercise is great for the abs and core, but most people shortchange it by rotating their torso too far.
Instead, shorten the range of motion by keeping your torso fairly perpendicular to the cable column. Don't rotate your torso towards the cable more than a few degrees as you begin each rep, and don't rotate your torso away from the cable more than a few degrees as you reach the end of the range of motion.
Fully rotating your torso in each direction at the beginning and end of the range of motion of each rep greatly reduces the rotational tension on your torso muscles. This improved version keeps more constant tension on the muscles to create and resist rotation, helping you make better use of your training time.