A simple rotation of the sandbag (or kettlebell, if no sandbag is available) while descending into a reverse lunge will challenge your strength and core stability in the transverse plane.
When you add in the power of a swing, what you wind up with is a really cool explosive movement – the swing requires decelerating the implement at the bottom of the movement before you explode from the lead leg into hip and knee extension.
Didn't it seem that the bodybuilders of yesteryear had bigger chests? (We're talking chest circumference here and not pec size, mind you.) Ellington thinks so and he knows why - it was all due to the all-but-lost art of ribcage expansion.