Ready to really challenge your overall core strength? Instead of putting that barbell on your back, try holding it in the crooks of your elbows, a move called the Zercher squat. By positioning the load lower and in front of your body, the Zercher squat challenges your back and shoulders to support the weight without stooping over, all while your hips and legs have to do the work of, y'know, squatting. But take it easy at first—this position is far more demanding than the usual squat, so make sure you start light and work your way to a comfortable weight. Here's a primer on how to do it.
Muscles worked: glutes, hamstrings, quads, lower back, and core.